Table of Contents Next Page


Introduction

Increasing attention has been paid in the last decade or two to the ways in which fisheries may impact marine mammal populations, and to the ways in which marine mammals might compete with, or cause damage to, fisheries. This subject was reviewed on a worldwide basis in 1984 (Northridge, 1984). Subsequently, numerous studies and investigations of marine mammal fishery interactions have been implemented around the world, and the aims of this revision of the previous FAO Fisheries Technical Paper are to summarise subsequent publications on this subject, and so demonstrate the overall scale of such conflicts.

In the 1984 report, a distinction was drawn between those interactions which were mainly operational, such as mammal entanglement, or damage caused by marine mammals to fishing gear, and those which are mainly biological, such as competition for fishery or food resources. Most research done recently has addressed the accidental killing of marine mammals in fishing operations, a source of mortality which has given rise to serious concerns about the status of several marine mammal populations.

In October 1990, the International Whaling Commission (IWC) convened a meeting on cetacean mortality in gillnet and trap fisheries, at La Jolla, in California, which brought together much of the recent work on cetacean entanglement in fishing gear. The executive summary of that meeting stated that kill rates of as low as 2% of a cetacean population may not be sustainable, depending on the life history of the species and the age and sex composition of the kill. Species including the baiji and the vaquita, and local populations of hump-backed dolphins, striped and bottlenose dolphins, and the harbour porpoise were singled out as being unlikely to be able to sustain current catch levels. The proceedings of this meeting, when published, should provide a more detailed account of many of the examples of cetacean mortality in fishing operations which are summarised here.

The extent to which marine mammals compete for food with fisheries has been studied somewhat less extensively. There have been several major impediments to understanding the ways in which marine mammals and fisheries might compete. One such problem is the lack of any detailed understanding of the dynamics of predation rates, and how these relate to either fluctuations in fish availability or fluctuations in marine mammal population size. Furthermore, relationships between marine mammal predation rates and fishery yields have proved very difficult to find or understand, outside of a strictly theoretical context. The whole problem is made more difficult in many cases by the problems involved in trying to quantify marine mammal diets which are often highly variable. Not surprisingly perhaps, few attempts have been made to investigate these competitive interactions.

As in the previous report, interactions are considered on the basis of FAO statistical areas, which are shown on the map above. Revised estimates of marine mammal population sizes, and recent investigations into marine mammal feeding habits have, in general, not been included in this revision, except where they are particularly relevant to a specific interaction.

Area 21 Northwest Atlantic

Eubalaena glacialis Northern right whale.
Entanglements of right whales continue at a relatively low rate in the northeastern United States; O'Hara et al (1986) review the available records and report 10 such entanglements in lobster trap lines (3), groundfish gillnets (5), a herring weir and a squid trawl (1) since 1976. Read (1990) adds a sixth record from Gulf of Marine groundfish gillnets. Most of these animals appear to have survived entanglement. Another record reported by the US to the IWC involved a right whale which died in a cod trap in Newfoundland in 1984. The population size in the northeast Atlantic remains unknown, but the largest number of animals sighted in one day was 70 (Schevill et al 1986). Even the occasional entanglement referred to above may pose a threat to the recovery of this depleted population.

Balaenoptera physalus Fin whale.
Twelve fin whales were reported entangled (but none was known to have died) in lobster trap lines and a gillnet in the northeastern USA from 1975 to 1986 (IWC 1987), and up to 3 per year have been reported entangled in inshore fishing gear in Newfoundland (Lien 1988). O'Hara et al (1986) record 5 out of 12 fin whales caught in inshore fishing gear in Newfoundland as being dead. Population size is unknown, but it seems unlikely that such levels of mortality would be a major influence on population dynamics.

Balaenoptera acutorostrata Minke whale.
Lien et al (1987) estimated average entanglement rates of around 11 minke whales per year in Newfoundland's inshore fisheries. Between 1979 and 1985 58% of such entanglements were in cod traps and 21% in gillnets (O'Hara et al 1986). Lien et al report that around 75% of such entanglements are mortalities. Smaller numbers of minke whales are reported entangled in the lobster trap fishery of New England (4 between 1975 and 1986). New England gillnet fisheries also entangle small numbers of minke whales (7 between 1976 and 1986), most of which are reported dead (O'Hara et al 1986). Read (1990) suggests some possible mortality in Gulf of St. Lawrence set gillnet fisheries, and also reports two minke whale deaths in Bay of Fundy herring weirs between 1980 and 1990. Population level impacts by these sorts of mortalities are unlikely to be significant, as, although population size is unknown, this is probably the most numerous of the baleen whales in this area

Megaptera novaeangliae Humpback whale.
Humpback whales are reported entangled in fishing gear relatively frequently, in traps and gillnets in Newfoundland and in several New England fisheries. In Newfoundland Lien et al (1987) reported between 813 (in 1980) and 255 (in 1985) collisions with inshore fishing gear annually, and estimated that about 48 humpbacks become entangled every year. This has resulted in gear damage of up to $384000 per year. Mortality of entangled whales has dropped from as high as 50% to about 7% in 1987 (i.e. about 3 per year latterly) due to the rescue programme initiated by Lien and colleagues. Groundfish gillnets, cod traps and salmon nets are all involved, with gillnets entangling humpbacks most frequently. As offshore capelin stocks have recovered, Lien et al report that humpback whale numbers inshore have declined, but entanglements still continue to be reported at similar levels, possible due to increased fishing effort, improved reporting, or to an increased population size of humpbacks in the Northwest Atlantic (ca 3000 Whitehead 1982).

Humpback whales have also been reported in the New England lobster trap fishery (3 since 1975) and in New England groundfish gillnet fisheries (14 between 1975 and 1990) (Read 1990). At least five of these incidents were fatal (O'Hara et al 1986). There are also records of two humpback whale entanglements in longlines in New England (O'Hara et al 1986), 2 or 3 in shad gillnets in eastern US waters, and six in herring weirs in the Bay of Fundy and Gulf of Maine (Read 1990). The latter, at least, were all released alive. The humpback whale population has recovered considerably over the past several decades, but commercial fisheries are still regarded as a potential threat to continued recovery (MMC 1989).

Mesoplodon bidens Sowerby's beaked whale.
There is one record of a Sowerby's beaked whale having become caught in a net in Quebec in 1984; it was released alive (Scialabba 1989).

Hyperoodon ampullatus Northern bottlenose whale;
At least one animal has been reported in inshore fishing nets in Newfoundland (O'Hara et al 1986).

Physeter macrocephalus Sperm whale.
Two sperm whales have been reported caught in lines (in 1979), at least one of which was from a lobster pot in New England; both animals were dead (IWC 1987, p189). No other interactions have been reported.

Monodon monoceros Narwhal.
O'Hara et al (1986) refer to a narwhal having been entangled in the inshore fisheries of Newfoundland.

Delphinapterus leucas White whale.
O'Hara et al (1986) also refer to white whale entanglement in inshore fisheries in Newfoundland, but no further details were given. Read (1990) refers to occasional entrapments in Gulf of St Lawrence groundfish gillnets, and in Canadian cod traps.

Pseudorca crassidens False killer whale.
Two false killer whales have been observed taken by the swordfish longline fishery operating off New England (O'Hara et al 1986).

Globicephala melaena Longfinned pilot whale
Pilot whales are recorded to have been taken in inshore fisheries around Newfoundland in small numbers (Leatherwood and Reeves 1983); Piatt and Nettleship (1987) reported 4 pilot whales caught in eastern Newfoundland between 1981 and 1984 in cod gillnets. Read (1990) reports their occasional entanglement in New England groundfish gillnet fisheries in Canadian cod traps, and in the New England-based swordfish driftnet fishery. In this latter fishery, operating largely along the edge of the continental shelf, about 10% of entangled cetaceans were pilot whales. Estimates of total catches are not yet available for this fishery. Pilot whales are also taken in foreign squid and mackerel trawls off the east coast of the US; a total of 249 pilot whales was reported for the years 1978 to 1988 from the fleets of 8 nations fishing in the mid-Atlantic bight, including 141 animals in 1988 (Waring et al 1989). It has been suggested that high catch rates are related to the distribution of fishing effort in particular areas of high pilot whale density (IWC 1990). The small cetacean sub-committee of the IWC noted that catches may have been higher in the past and could have affected the status of the stock (IWC 1990).

Lagenorhynchus albirotris White-beaked dolphin.
Read (1990) refers to occasional captures in groundfish gillnet fisheries in the Gulf of St. Lawrence. Quantitative data are unavailable.

Lagenorhynchus acutus Atlantic white-sided dolphin.
There are very few data on catches of white-sided dolphins in this area, although several authors suggest that captures occur fairly frequently in set nets and traps, in Newfoundland and New England, and there are also reports of some entanglements in the small New England mackerel driftnet fishery (Read 1990). Catches are also reported in the foreign mackerel and squid trawl fisheries, but infrequently (3 animals 1978-1985 reported : O'Hara et al 1986).

Tursiops truncatus Bottlenose dolphin.
Bottlenose dolphins are reported caught in small numbers in the mackerel and squid trawl fisheries of the mid-Atlantic Bight (3 reported in 8 years), in driftnet fisheries in Delaware (1 animal recorded), in the swordfish longline fishery (1 record), and apparently somewhat more frequently in inshore net fisheries in and around Chesapeake Bay. Scott el al (1988) report that up to 20% of stranded animals in Virginia may have died from incidental capture, and suggest that in this area fishery mortality may have a significant effect on local populations, though an adequate assessment is hampered by a lack of information on stock distribution. Read (1990) reported that 15% of cetaceans entangled in the swordfish driftnet fishery operating from New England were bottlenose dolphins. No estimate of total catch is available from this fishery.

Grampus griseus Risso's dolphin
A few accidental captures have been reported in the New England lobster trap fishery and the Atlantic trawl fisheries for mackerel and squid (O'Hara et al 1986), but such incidents seem to be fairly rare. Risso's dolphins are also taken in unknown numbers (14% of the cetacean entanglements observed) in the New England swordfish driftnet fishery (Read 1990).

Stenella coeruleoalba Striped dolphin.
O'Hara et al (1986) report the capture of one individual in a gillnet fishery in the Chesapeake Bay area. Read (1990) reported that striped dolphins formed 4% of the cetacean catch of the New England swordfish driftnet fishery.

Stenella attenuata Pantropical spotted dolphin.
The only reported entanglements of this species appear to be in the New England swordfish driftnet fishery, where they formed 6% of the observed catch (Read 1990).

Delphinus delphis Common dolphin.
Catches of common dolphins have been reported relatively frequently in the mid-Atlantic bight trawl fisheries for mackerel and squid, with 199 animals reported between 1977 and 1988 (Waring et al 1989). 62% of these were taken in the foreign squid trawl fishery which has now been terminated. Catches of perhaps 20 per year continue in the mackerel fishery (Cranmore 1988). Catches are also relatively frequently observed in the New England swordfish driftnet fishery, where this species formed 39% of observed cetacean catches (Read 1990). The impact on local stocks is not known.

Phocoena phocoena Harbour porpoise.
>Harbour porpoises are the most frequently recorded cetacean species taken accidentally in area 21. Catches in Newfoundland in inshore fishing gear (gillnets and traps) have been estimated to amount to around 140 per year, in eastern Newfoundland (Piatt and Nettleship 1987), whilst Lien (1987) gave tentative estimates of 1800–3000 per year for the whole of Newfoundland and Labrador. Catches in Greenland continue in the salmon driftnet fishery, but recent estimates of numbers caught are lacking.

Catches also occur throughout much of the rest of the US and Canadian coasts: Read and Gaskin (1988) examined catches in the Bay of Fundy and estimated annual catches to exceed 100. High catches have also been reported in gillnets in the Gulf of St Lawrence (IWC 1990), while total catches in the Gulf of Maine / Bay of Fundy area may be from 280–800 per year. The total population in the Gulf of Maine / Bay of Fundy region was estimated at around 8000–15000 (Kraus et al 1983), and Woodley and Read (1990) have estimated this population should not be able to sustain catches of more than around 4% per annum. Read and Gaskin (1990) found evidence of changes in the reproductive parameters in this stock, suggesting a population decline. The IWC small cetacean subcommittee therefore suggested that current levels of incidental mortality pose a serious threat to the harbour porpoise sub-population in this area. Sub-populations in the Gulf of St Lawrence, Newfoundland, Labrador and Greenland are also subjected to large directed or incidental catches, but population status in these areas remains unknown (IWC 1990).

Phoca vitulina Common seal.
Common seals are caught in fishing gear not infrequently in both Canada and the US. Piatt and Nettleship (1987) estimated catches of around 30 per year in eastern Newfoundland, while around 20 per year are thought to be taken in gillnet fisheries in Maine, and more rarely on longline hooks, in purse seines and in lobster trap fisheries (Gilbert and Wynne 1985, 1988, Cranmore 1988). The effects of seal predation on Canadian fisheries was assessed by a Royal Commission on seals and the sealing industry in Canada (Anon 1988a), who, on the basis of numerous assumptions, estimated that common seals might cost the fishing industry $1.6 million to $3.7 million.

Phoca groenlandica Harp seal
Harp seals have been taken in large numbers in the inshore fisheries of Newfoundland. Piatt and Nettleship estimated catches of 746 per year in eastern Newfoundland, whereas numbers may be much higher in some other areas (500–2000 in Old Fort, Quebec) (Lien et al 1987). Total numbers caught are unknown, as is the impact on the population. Harp seal predation has been estimated, on the basis of numerous simplifying assumptions to cost $23 million to $75 million per annum (Anon 1988a).

Cystophora cristata Hooded seal
Very small numbers have been reported caught in inshore fisheries in Newfoundland (Piatt and Nettleship 1987). Predation by hooded seals on demersal fish has been claimed to cost Canadian fisheries $87–207 thousand (Anon 1988a).

Halichoerus grypus Grey seal.
Grey seals are caught in small numbers in the New England groundfish fisheries: 4 were reported caught in 1984 (Gilbert and Wynne 1985) for example. Impacts on the local population are unknown. It seems likely that, given the larger numbers present in Canadian waters, that accidental catches occur there also. The Royal Commission on seals and the sealing Industry in Canada assumed that 42–63% of grey seal food was commercial demersal species and estimated, on the basis of several other assumptions, an annual loss to Canadian fisheries of $30–84 million because of seal predation.

Recent information on interactions with fisheries could not be located for the following species which occur in this area: Balaena mysticetus, B. musculus, B. borealis, B. edeni, Mesoplodon densirostris, M. mirus, M. europaeus, Ziphius cavirostris, Kogia breviceps, Orcinus orca, Odobenus rosmarus, Phoca hispida. It should be noted, however, that Read (1990) reported that 12% of cetaceans caught in the swordfish driftnet fishery were as yet unidentified Ziphiids.

Area 21 Summary.

The species most affected by accidental entrapments in fishing gear in this area is the harbour porpoise. Catches of certain of the large whales, notably humpbacks and right whales may also be considered significant, while bottlenose dolphins may be affected locally (in Virginia for example).

The major fisheries involved with marine mammals are the Greenlandic driftnet fishery for salmon, the inshore trap and gillnet fisheries of Newfoundland (and probably elsewhere in eastern Canada which remains comparatively less well studied), the gillnet fisheries and lobster trap fisheries of New England, the offshore midwater trawl fisheries, and the New England swordfish driftnet fishery.

The harbour porpoise may be most severely affected, by gillnet fisheries in the Bay of Fundy/Gulf of Maine region, but also possibly in other gillnet and trap fisheries further north. Humpback whale entanglement, although apparently not hampering recovery of the population in this area, is still a cause for concern as a potential problem. Catches of right whales are not so frequent, but as this population may still be in a precarious state they are also considered to be a potential threat to population recovery.

Area 27 Northeast Atlantic

Balaenoptera acutorostrata Minke whale.
The only record of a minke whale entanglement in this area which could be found is that of a minke whale which was caught in a lobster creel line in Orkney, before escaping, in 1986 (Hislop pers. comm.). The stomach contents of 28 minke whales killed in Norway in 1988 have been examined, and were found to contain herring, cod and krill (IWC 1990) but interactions with fisheries have not been studied yet.

Megaptera novaeangliae Humpback whale
Malinga and Skora (1991) report a single record of this species from the Baltic Sea in 1979. This individual was entangled in a driftnet in Gdansk Bay, but was released alive.

Globicephala melaena Longfinned pilot whale.
Occasional catches of pilot whales have been reported in several fisheries in the Northeast Atlantic. One was reported drowned in a lobster creel line in Orkney in 1984, 1 in a purse seine off Scotland in 1986, three have been reported in set gillnets off Cornwall (2 released alive), and there have been further unconfirmed reports of captures in purse seines off Cornwall and even a possible record of one in a demersal trawl in the same area (Northridge 1988). Perez and Nores (1988) record one pilot whale taken in fishing gear in northern Spain between 1977 and 1988. These isolated accounts are possibly indicative of sporadic accidental mortalities, but further information on the scale of such mortalities or their impact on populations is lacking.

Lagenorhynchus albirostris White-beaked dolphin
White-beaked dolphins are among the more common species in northern European waters and are reported in small numbers in the herring fisheries; 4 are known to have died in 2 separate incidents in 1987 off Scotland, and there is an unknown mortality of white-beaked dolphins off the Yorkshire coast (northeast England) every summer when Dutch midwater herring trawlers operate in that region (Northridge 1988). Malinga and Skora (1991) referred to two individuals being caught by an unspecified fishing boat in the Baltic in the 1980's. There are also unconfirmed reports that this species is caught in Irish salmon driftnet fisheries. Population size is unknown and impacts have not been assessed.

Lagenorhynchus acutus Atlantic white-sided dolphin
One white-sided dolphin was recorded taken in the northeast of England in 1985 in a trawl or a seine net (IWC 1987). No other recent records of accidental captures could be found.

Tursiops truncatus Bottlenose dolphin.
Bottlenose dolphins have been reported caught in gillnets in the south of England in very small numbers, and one is also reported to have died after becoming entangled in a net line (Northridge 1988). Unconfirmed reports indicate some mortality in Irish driftnet fisheries, and there are also reports of occasional captures in French fisheries (Scialabba 1989). Impacts on local populations are not known.

Grampus griseus Risso's dolphin.
Apart from Collet's (1981) record of incidental capture, none other could be found.

Stenella coeruleoalba Striped dolphin
Recorded “sporadically” by Perez and Nores (1988) in fishing gear in northern Spain, this species might also be expected in French and Portuguese Atlantic fisheries, but records are generally lacking. Estimates of catches in the French albacore driftnet fishery for 1990 were 420–460 dolphins (Antoine 1990); the species involved were both striped and common dolphins.

Delphinus delphis Common dolphin.
One of the most frequently reported cetaceans taken in fishing nets in the Northeast Atlantic. Common dolphins are taken in Irish salmon driftnets in unknown numbers (Berrow pers. comm.). An Irish research vessel is reported to have fished 1 Km of driftnet over a three week period for 4 years and taken 2 common dolphins. They have been reported in mackerel purse seines in the southwest of Britain (Pascoe 1986), in English midwater trawl research cruises in the Channel (Northridge 1988), and in an unidentified type of trawl in the Channel (MacBrearty Pers. Comm.). There is a considerable accidental catch of small cetaceans in the English bottom set net fishery off the southwest coast of England, which is thought to consist mainly of this species, although samples have not been obtained. Total annual catches on the basis of very a limited number of interviews with fishermen may number in the hundreds (Northridge 1988). Catches of common dolphins in various French fisheries continue, and large numbers of animals with evidence of entanglement have been washed up on French Atlantic coasts in the past few years. There is also a large French gillnet fishery in this area operating along similar lines to the English one, as well as several trawl fisheries. The French driftnet fishery for albacore in the Atlantic in 1990 was estimated to take around 420– 460 dolphins (Antoine 1990), apparently both this species and striped dolphins. On the North coast of Spain, Perez and Nores (1988) list 7 records of common dolphins taken in fishing gear between 1977 and 1987. Reiner (1980) also listed 11 common dolphins caught in fishing nets in Portugal in 1980. Sequeira (1990) indicated that common dolphins are frequently taken in coastal Portuguese fisheries: 47% of those reported were from gillnet fisheries. The scale of incidental catches of this species is clearly large. (Collet (1983) estimated 2000–2500 dolphins, mainly common dolphins taken in French Atlantic fisheries per annum), but impacts on the population are not known.

Phocoena phocoena Harbour porpoise.
Harbour porpoises are also taken frequently in numerous fisheries throughout European waters. Bjorge and Oein (1989) collected 96 harbour porpoises in 2 months from 580 salmon driftnet fishermen in coastal Norwegian waters of 1988. This fishery has now been closed. Catches have been recorded in small numbers in the Baltic, in Polish salmon and herring nets (Skora et al 1988) and in German set nets for cod (Kremer and Schulz 1990). In Swedish waters Lindstedt and Lindstedt (1989) reported 149 animals in fishing gear (86% in gillnets the rest mainly in trawls) between 1973 and 1987 and a further 23 in June to December 1988. Kinze (1990a) reported on catches in Denmark which occur primarily in set gillnet fisheries for cod and flatfish in Danish waters, and although it has not been possible to determine the total numbers caught, one individual vessel is known to have taken 47 animals in 1989, and 94 animals have been recovered between 1986 and 1989. Total catches by Danish vessels are presumed much higher than this. Kinze (1990b) proposed an annual catch of some 750 porpoises by gillnetters from one port alone in Jutland. A few catches have been recorded at the Faroe Islands, in herring nets (Heje Larsen 1990). In Scotland porpoises are taken in groundfish trawl fisheries in Shetland and elsewhere; total numbers caught are not known, but exceeded 20 in 1988/89. Catches occur in trawl fisheries elsewhere in Britain in unknown numbers, and sporadically in gillnet fisheries mainly along the east coast of England. Some animals have even been reported foul-hooked on longlines. Catches of harbour porpoises seem to occur in most British fisheries, but the scale of the total catch is unknown and so is the impact on the population or populations (Northridge 1988). In Ireland porpoises are frequently taken in set gillnets and drift gillnets, but again the overall scale of catches remains unknown (Berrow pers. comm.). In France harbour porpoises are not frequently encountered, but in Northern Spain, Perez and Nores (1989) found that this is the most commonly caught cetacean in fishing gear, 29 specimens having been recovered from 1977– 87. In Portuguese waters too, harbour porpoises are taken in fishing gears in unknown numbers with other species (Sequeira pers comm). Overall harbour porpoises are taken in more types of fishing gear, and possibly in larger numbers, than any other marine mammal species in this area. Impacts on populations have not been assessed, but as this species is primarily coastal, and therefore comes into contact with fisheries throughout its range, and in view of some apparently substantial mortalities, catches in fishing gear must be considered as a potentially important factor in their life history in this as in other areas.

Phoca vitulina Common seal
Catches have been reported in midwater sprat trawls in the Wash in England (some tens per year when the fishery operates, Northridge 1988), and in protective nets around Scottish salmon farms, where as many as several hundred per year may drown (Ross 1988). Catches are also reported in other static gears around Britain (Northridge 1988), in France and Denmark (Scialabba 1989). Recent data on catches of common seals in other parts of Europe are lacking, but it is reasonable to assume that they occur elsewhere too. Numbers of this species have been greatly reduced, especially in the eastern and southern North Sea, after a viral epidemic in 1988. Feeding habits have recently been studied by Pierce et al (1990) in Scotland and by Harkonen (1988) in the Kattegat and Skagerrak. Clupeids, sandeels and small gadoids predominated. Competition with fisheries has not been assessed in detail. McCarthy (1985) found that common seals were mainly responsible for damage to salmon in gillnet fisheries in Ireland which ranged from 8% to 44.5% of the catch. Occasionally some animals drown in this fishery.

Phoca groenlandica Harp seal
In Norway in recent years there have been very large catches of harp seals, largely in cod set net fisheries along the northern coast of Norway. At least 37 000 harp seals died in Norwegian waters in this way in 1987, but large scale mortalities in net fisheries have been reported since the late 1970's in this area; many of the seals which died were young and in poor condition (Oritsland pers. comm.). It is possible that these seals may have been affected by declines in capelin and other fish stocks in the Barents Sea. Catches have been much reduced since the peak year of 1987, and coincidentally capelin stocks have been recovering.

Halichoerus grypus Grey seal.
Grey seals have been reported in a wide range of fishing gears. In Britain catches are highest in set net fisheries, including a small tangle net fishery in Scotland where catch rates appeared to be quite high (one fisherman took 36 in one season), and in set net fisheries in Cornwall and Northeastern England. Most animals recorded in such nets were young, and from tagging results it appears that a minimum of between 1 and 2% of seal pups end up drowned in fishing gear (Northridge 1988). Grey seals are also reported to be caught in unspecified numbers in Sweden, Finland, Norway and France (Scialabba 1989). Damage to fisheries by grey seals is widely reported. Heap et al (1986) found that around 5% of fish caught in inshore set net fisheries were damaged by seals, and McCarthy (1985) found that grey seals were partly responsible for damage to salmon caught in gillnets which ranged from 8 to 44.5% of the catch. Competition with fisheries was examined by Harwood and Croxall (1988), who found that consumption of most prey species by North Sea grey seals was one or two orders of magnitude less than the fishery yield; exceptions were found for flounders, dabs and ling where fishery yields were very small.

Other species which occur in this area, but for which no recent information on interactions with fisheries has been found include: Eubalaena glacialis, Balaena mysticetus, Balaenoptera physalus, B. musculus, B. borealis, Mesoplodon bidens, M grayi, M. mirus, Ziphius cavirostris, Hyperoodon ampullatus, Physeter macrocephalus, Kogia breviceps, Monodon monoceros, Delphinapterus leucas, Steno bredanensis, Pseudorca crassidens, Orcinus orca, Odobenus rosmarus, Erignathus barbatus, Cystophora cristata, Monachus monachus.

Area 27 Summary

The major species affected by accidental catches in fishing gear in this area are the harbour porpoise and the common dolphin. Competition with fisheries has only been examined in relation to the grey seal.
The most important fisheries in terms of their accidental catches are the gillnet fisheries, mainly set gillnet fisheries, which are distributed throughout coastal waters of this region, and in some places extend for many tens of kilometres offshore. Trawls may also take relatively large numbers of some species in some places, for example harbour porpoises in Shetland, or possibly common dolphins where mackerel midwater trawls are used.

The impact of accidental catches on common dolphin and harbour porpoise populations is not known. Common dolphin populations have not been noticed to be in decline in this region, even though catches may number in the thousands. It has been suggested that harbour porpoise populations may have declined in some areas, such as the Baltic and southern North Seas, but what role, if any, fisheries may have had in such a decline is not clear.

Area 31 Western Central Atlantic

Eubalaena glacialis Northern right whale.
Burn and Scott (1988) refer to two individuals which had been incidentally caught in (unspecified) fisheries in Florida and North Carolina respectively between 1974 and 1984. Given the precarious state of this population (which breeds in inshore waters of the southeastern US) even such a small number of entanglements may be significant.

Megaptera novaeangliae Humpback whale.
Burn and Scott (1988) also report the incidental entrapment of 3 humpback whales in Virginia and North Carolina between 1974 and 1984. Vidal (1990) refers to the capture of a humpback whale calf in a gillnet in the Dominican Republic.

Kogia breviceps Pygmy sperm whale
Again, 3 records of incidental capture are recorded by Burn and Scott (1988) in Virginia and North Carolina between 1974 and 1984. Vidal (1990) reports the capture of one individual taken in a coastal gillnet fishery in the Gulf of Morrosquillo, Colombia, in 1988.

Sotalia fluviatilis Tucuxi
Van Waerebeek (1990) reports on incidental captures of small cetaceans in gillnets in French Guiana, which he assumed included this species. The scale of the interaction has not been established. Vidal (1990) also reports the capture of an individual in 1986, in a gillnet fishery in the mouth of the Sinu river, Colombia.

Pseudorca crassidens False killer whale.
Japanese longliners are reported to have taken at least 8 false killer whales in this area between 1978 and 1987, according to US observer reports (Burn and Scott 1988).

Orcinus orca Killer whale
A killer whale is reported to have drowned in a driftnet in Trinidad in 1987 (Ottley pers comm), but this appears to be the only recorded interaction in this area.

Globicephala macrorhynchus Short-finned pilot whale.
Burn and Scott (1988) refer to the accidental capture of 15 pilot whales in the Japanese longline fishery, which were recorded by US observers, between 1978 and 1987.

Tursiops truncatus Bottlenose dolphin
The bottlenose dolphin is the most widely caught species in this area. Reynolds (1985) reviewed the information on interactions between bottlenose dolphins and fisheries in the southeastern US. In North Carolina the main interaction was with the menhaden purse seine fishery, in which around 15 bottlenose dolphins a year were reported to die, with additional mortalities in other fisheries. In South Carolina the sturgeon and shad gillnet fisheries were also reported to have trapped about 15 bottlenose dolphins per year. The sturgeon gillnet fishery and shad offshore gillnet fishery were subsequently terminated, so that incidental mortality in the inshore shad gillnet fishery is likely to be the main source of such mortality at present. A few records of entrapment of bottlenose dolphins in gillnets in Georgia and Florida were also recorded, but Reynolds also records one informant indicating a large scale mortality (hundreds) of unspecified dolphins in a tuna net fishery off Florida. The nature of this fishery was not clear, and the claim remains unsubstantiated. Dolphins are reported to damage fishing gear on both coasts of Florida, and are apparently shot at by mackerel fishermen. In the Gulf of Mexico, small numbers of bottlenose dolphins may also be killed in shrimp trawls and gillnets, while a few may be shot by fishermen because of net damage. Bottlenose dolphins are the most abundant coastal cetacean species in this area, and so seem likely to be the most at risk from entrapment in coastal fisheries. Ottley (pers comm) reports that dolphins are sometimes taken in driftnets in Trinidad, but no species identification has been made. Van Waerebeek (1990) reported a possibly large incidental capture of small cetaceans, which may have included bottlenose dolphins, in French Guiana. Vidal (1990) reports the capture of one individual in a gillnet in a Colombian coastal fishery. Other gillnet fisheries in Mexico, for example may also be expected to impact bottlenose dolphins in this area. Reynolds (1985) notes that even small numbers of animals killed in fishing gear could have a severe impact on localised populations.

Grampus griseus Risso's dolphin.
Vidal (1990) reported the capture of an individual in Colombia in 1989 in a gillnet fishery.

Stenella longirostris Spinner dolphin.
Spinner dolphins have been reported taken in the Japanese longline fishery (1 animal from 1978–1987 recorded). Another individual is recorded taken in unspecified fishing gear in Florida (Burns and Scott 1988).

Stenella attenuata Pantropical spotted dolphin.
Burns and Scott (1988) provide 2 records of catches in the Japanese longline fishery.

Stenella frontalis Atlantic spotted dolphin.
Vidal (1990) records one individual taken in a gillnet fishery in Colombia in 1989.

Delphinus delphis Common dolphin.
Six common dolphins have been recorded in the Japanese longline fishery (Burns and Scott 1988).

Phocoena phocoena Harbour porpoise
Although at the edge of its range in the northern part of this area, 3 records of entanglement have been collected from Virginia and North Carolina in unspecified fishing gears (Burns and Scott 1988). Read (1990) also referred to catches of this species in US coastal gillnet fisheries in the southern end of its range, and recommended that these should be investigated further.

Trichechus manatus Caribbean Manatee.
Between 1974 and 1984 at least 30 manatees have been reported entangled in Florida crab trap lines, and at least 2 are known to have died. In view of the small population size, such incidents may be significant.

Other species which are known to occur in this region, if only as stragglers, but for which no recent specific information could be found, include: Balaenoptera physalus, B. musculus, B. acutorostrata, B. borealis, B. edeni, Mesoplodon densirostris, M. europaeus, M. mirus, Z. cavirostris, Physeter macrocephalus, Steno bredanensis, Peponocephala electra, Feresa attenuata, Lagenodelphis hosei, Stenella coeruleoalba, Stenella clymene, Inia geoffrensis, (Zalophus californianus), Phoca vitulina and Monachus tropicalis (extinct).

Area 31 Summary.

The species most frequently involved in fishery interactions is the bottlenose dolphin. Right whales and manatees are affected in small numbers but their small population sizes may still mean that this is a significant interaction.

Inshore gillnet fisheries appear to be frequently involved in bottlenose dolphin (and possibly tucuxi) captures. The relatively large number of records of catches in the Japanese tuna longline fishery in this area is almost certainly due to the observer coverage in this fishery, rather than to any relatively higher catch rate in this fishery than in others. The crab fishery in Florida may be important with regard to manatees.

Interactions with fisheries remain almost undocumented in the southerly or non-US parts of this region; the recent report of van Waerebeek (1990) indicates the possibility that significant interactions may occur which have not been reported.

Area 34 Eastern Central Atlantic

Globicephala macrorhynchus Short-finned pilot whale
Heimlich-Boran (1990) reports that some of the pilot whales being studied in the Canary Islands bear net scars, but no information on fishery related mortality is known.

Tursiops truncatus Bottlenose dolphin
Scialabba (1989, citing personal communication with Maigret) reports that this species is taken in unknown numbers by foreign pelagic trawlers off the Mauritanian coast, and in coastal gillnets too. No further details are available.

Delphinus delphis Common dolphin.
This species is also said to be taken in foreign pelagic trawls off the Mauritanian coast in unknown numbers (Scialabba 1989, citing personal communication with Maigret).

Monachus monachus Mediterranean monk seal
Entanglements in coastal gillnets have been reported in Mauritania (Scialabba 1989 citing personal communication with Maigret), but no other published account or quantified data could be found.

Trichechus senegalensis West African Manatee.
Manatees are reportedly caught in coastal and riverine net fisheries in Senegal, at least (Scialabba 1989), and presumably throughout much of the rest of their range. Reeves et al (1988) also report that manatees are caught in fishing gear (deliberately as well as accidentally) in Sierra Leone. The impact of accidental catches in fishing gear is unknown. In Sierra Leone, fishermen also report that manatees remove fish from gillnets (Reeves et al 1989); this has not yet been confirmed.

Other species present in the area, for which no recent information on interactions with fisheries could be found include: Eubalaena glacialis, Balaenoptera physalus, B. musculus, B acutorostrata, B. borealis, B. edeni, Megaptera novaeangliae, Mesoplodon densirostris, Ziphius cavirostris, Physeter macrocephalus, Kogia breviceps, Steno bredanensis, Sousa teuszii, Peponocephala electra, Feresa attenuata, Pseudorca crassidens, Orcinus orca, Grampus griseus, Stenella longirostris, Stenella coeruleoalba, Stenella attenuata, S. frontalis, S. clymene, Phocoena phocoena.

Area 34 Summary.

Very little information is available on marine mammal fishery interactions in this area. Information is so sparse that it would be difficult to guess which species are most frequently caught. The Atlantic hump-backed dolphin and West African manatee are both coastally distributed animals endemic to this region which might be considered most likely to be at risk from inshore fishing activities. Monk seals are also potentially vulnerable as one of the rarest of all marine mammals, but as yet there is little indication that the size of the Mauritanian population has been affected by fisheries. The harbour porpoise, often taken in coastal fisheries in other parts of its range, also occurs in northern waters of this area.

There are some large pelagic trawl fisheries operating over much of the west African coast, as well as purse seine fisheries. The former may certainly be expected to take pelagic dolphin species at least, while there have been previous reports that the latter may make sets on dolphin associated tuna schools, although the extent to which this still continues is not known. Coastal fisheries include many gillnet fisheries which would be expected to take manatees and other coastally distributed species.

There is no indication as to what effect, if any, these fisheries may be having on marine mammal populations in this area, nor have any assessments of competition with fisheries been made.

Area 37 Mediterranean and Black Sea

Balaenoptera physalus Fin whale.
A young fin whale was reported by Di Natale (1989) to have become entangled in a longline to the east of Sicily.

Balaenoptera acutorostrata Minke whale.
Di Natale (1989) reports that two minke whales have been found in unclassified gillnets in the French region.

Ziphius cavirostris Cuvier's beaked whale.
Bello (in press, cited by Di Natale 1989) reports that a Cuvier's beaked whale was taken by a longline in the southern Adriatic. There are further records from the recently terminated Italian swordfish driftnet fishery; two animals out of 150 identified as being caught in fishing gear (presumably driftnets), were of this species (Notobartolo di Sciara 1990).

Physeter macrocephalus Sperm whale.
Apparently rather unusually, sperm whales have been reported fairly frequently in fishing gear in the Mediterranean. Di Natale (1989) refers to one taken in a coastal trammel net, and in a trawl too. Catches in driftnets were fairly frequently encountered: Notobartolo di Sciara (1990) lists 150 stranded cetaceans which were thought to have died in fishing gear (presumably mainly driftnets), of which 24 were sperm whales. Di Natale (1989) considered mortality of sperm whales in driftnets to be the most important mortality factor for sperm whales in the central Mediterranean.

Pseudorca crassidens False killer whale.
Di Natale (1989) refers to 2 false killer whales taken by longlines, in the Tyrrhenian Sea off the Calabrian coast.

Orcinus orca Killer whale.
Di Natale (1989) refers to the capture of a killer whale in a tuna trap in Sicily.

Globicephala melaena Long finned pilot whale
Pilot whales are reported to have been taken in the swordfish driftnet fishery too. 7% of animals recorded by Notobartolo di Sciara were pilot whales.

Tursiops truncatus Bottlenose dolphin.
Bottlenose dolphins have been reported caught in longline, trammel net, driftnet and trawl fisheries in the Mediterranean (Di Natale 1989). Di Natale suggests they may feed on fish taken in trawls, and also reports that they are said to raid coastal set nets in Italy, and to take squid from lines in the Straits of Messina. 9% of Notobartolo di Sciara's (1990) sample of cetaceans were bottlenose dolphins, suggesting a frequent incidental catch in the driftnet fishery. Damage by dolphins has been reported in the inshore fisheries of Tunisia (GFCM 1989), but the species of dolphin and nature of the damage were not recorded. Bottlenose dolphins, however, are the most likely species, in view of the damage reported elsewhere.

Grampus griseus Risso's dolphin
Di Natale (1989) refers to catches in longlines (two individuals), set nets (in France) and driftnets in Italy. 5 (3%) of Notobartolo di Sciara's sample were Risso's dolphins.

Stenella coeruleoalba Striped dolphin
Magnaghi and Podesta (1987) refer to the capture of 8 striped dolphins in a tuna purse seine operation in the Ligurian Sea, 5 of which died. This is apparently not a common occurrence. Di Natale (1989) refers to additional captures in longline, trawl and tangle net fisheries. The striped dolphin was the most frequently taken species in the driftnet fishery (68/150 or 45% of Notobartolo di Sciara's sample). On the basis of interviews with several hundred fishermen involved in this fishery, Di Natale (Pers. Comm.) estimated that total cetacean catches may have exceeded 5000 cetaceans in some years, suggesting a very large number of striped dolphins were taken. The impact on the population is unknown.

Delphinus delphis Common dolphin.
Recorded in both trawl and trammel nets (Di Natale 1989), common dolphins are also the second most numerous (32%) cetacean species in the Turkish Black Sea, where population numbers been recovering after intensive exploitation, and may now number around 150 000 (Celikkale et al 1989); fishermen there complain that the increasing cetacean populations are the reason for declining fish yields (Celikkale 1990).

Phocoena phocoena Harbour porpoise
More or less restricted to the Black Sea, this is the most numerous of the 3 resident cetacean species there, constituting 53% of the total, with an estimated population size of around 240 000. Catches of cetaceans are reported to occur, but the numbers, species and gear types involved are not mentioned (Celikkale 1990), although trawls and purse seines are the major gear types used in Turkish waters. As with the common dolphins, Celikkale (1990) reports that fishermen blame increasing cetacean populations for declines in fish yields.

Monachus monachus Mediterranean Monk seal.
Deliberate and accidental killing of monk seals are among the most important threats to the survival of this species (UNEP 1990). Eight monk seals are reported to have drowned in fishing gear in the Ionian Sea since 1978, of which 3 are known to have died in trammel nets, 2 in gillnets, while 1 was taken on a longline (Anon 1988b). Accidental catches elsewhere have not been quantified but continue. Di Natale and Notobartolo di Sciara (1990) for example, refer to continuing occasional catches of monk seals in Algerian coastal gillnets. Fishermen in Rhodes are reported to have shot dead 20 animals in 1985 in retaliation for damage to gear (Naturopa 1985). The total population may now number only around 600 (UNEP 1990).

Other species known to occur in this area, but for which information on fishery interactions could not be found include: Eubalaena glacialis, Megaptera novaeangliae, Mesoplodon bidens, Hyperoodon ampullatus, Steno bredanensis.

Area 37 Summary

The species most affected by interaction with fisheries appear to be monk seals, striped dolphins and sperm whales. Bottlenose dolphins are also taken in a wide variety of gears, and are reported to cause damage to some fisheries locally.

The most important fisheries with regard to marine mammal fishery interactions are generally the gillnet fisheries. One major driftnet fishery has recently been closed down, but others continue on a smaller scale, and set net fisheries are widespread.

Competition with marine mammals is claimed in the Black Sea, and also recently in Italy (Di Natale pers comm), where in southern areas some fishermen are calling for a reduction in dolphin numbers to curb a perceived competitive threat. The problem is currently the subject of study.

Area 41 Southwest Atlantic

Megaptera novaeangliae Humpback whale.
Siciliano and Lodi (1989) report a single humpback whale entanglement in a gillnet near the Abrolhos Archipelago in Brazil; they also state that numbers of humpback whales off the Brazilian coast appear to have increased in recent years. Praderi (1990) refers to one humpback entangled in Uruguayan shark gillnets.

Physeter macrocephalus Sperm whale
Pinedo et al (1986, cited by Scialabba 1989) report occasional sperm whale captures in unspecified gear types in Brazil.

Sotalia fluviatilis Tucuxi
Tucuxi are reported to become entangled in beach seines and, more frequently, in set gillnets and driftnets throughout their range in the central Amazon (da Silva and Best 1990). These authors suggest that differences in sizes and species of fish taken by fishermen and Amazonian cetaceans is likely to restrict competition between the two. Canella and Ximenez (1990) also refer to tucuxi entanglement in gillnets in the northern region of Brazil, especially in Baia de Marajo, Algodoal, Raposa and Vieira, Sao Luis Island, and to its use for shark bait in Bahia.

Pseudorca crassidens False killer whale
Also reported to be taken occasionally in Brazilian fisheries (Pinedo et al 1986, cited in Scialabba 1989).

Globicephala melaena Long finned pilot whale
Records of 6 pilot whales taken on longlines in Brazilian waters between 1980 and 1985 were reported by Pinedo et al (1986 cited in Scialabba 1989). Bastida and Bastida (1984, cited in Goodall, Galeazzi and Lichter 1988) also report a pilot whale taken in commercial offshore fisheries (purse seine or trawl).

Lagenorhynchus obscurus Dusky dolphin.
Dusky dolphins are reported to be taken in a purse seine fishery off the Argentine coast near Necochea (Monzon et al 1990); 50–100 dusky and common dolphins per year may be taken. An unknown number also becomes entangled in a similar purse seine fishery at Mar del Plata (Crespo and Corcuera 1990). The Mar del Plata surface trawl fishery may also take a few every year, and further small scale catches are reported to occur in unspecified gears in southern Argentina (Scialabba 1989). 23 further records are provided by Goodall, Galeazzi and Lichter (1988), taken in anchovy nets (17) and shrimp nets (3) in Chubut, and shrimp nets (3) in Santa Cruz Province. Crespo and Corcuera (1990) also refer to dusky dolphin mortalities in a trawl fishery in Chubut: the scale of these catches remains unknown.

Lagenorhynchus australis Peale's dolphin
Peale's dolphins have been reported taken in set nets in Tierra del Fuego, but the overall numbers involved are not known (Goodall, Galeazzi and Lichter 1989). One individual was collected from nets in Tierra del Fuego in 1987/8 (Lichter and Goodall 1989).

Tursiops truncatus Bottlenose dolphin
A bottlenose dolphin was reported by Batista and Batista (1984, cited in Goodall Galeazzi and Lichter 1988) to have been taken in an inshore net fishery off Mar del Plata in 1982, and Praderi (1990) refers to three caught in Uruguayan shark gillnets since 1974.

Delphinus delphis Common dolphin.
Common dolphins are also reported taken, with dusky dolphins, at a combined rate of about 50–100 a year in a purse seine fishery off Necochea, Argentina (Monzon et al 1990), and in unknown numbers in a trawl fishery in Chubut (Crespo and Corcuera 1990).

Cephalorhynchus commersonii Commerson's dolphin.
Commerson's dolphin is reportedly taken in trawl fisheries in Chubut, Tierra del Fuego and Peninsula Valdez, in tens of individuals per year (Scialabba 1989). Goodall et al (1988) suggest that some may also be taken in Tierra del Fuego for crab bait, as they are in Chilean Tierra del Fuego, but probably in smaller numbers than in Chile. Incidental mortality in set nets for robalo (Eleginops maclovinus) still continues, but the numbers involved are not known (Goodall et al 1988); incidental catches in inshore gillnets are reported also in the Provinces of Chubut and Santa Cruz (25 recorded in 3 years: Goodall, Galeazzi and Lichter 1988), and in Tierra del Fuego where a minimum 14 animals (+6 more ‘probably’) were drowned in nets in 1987/8 (Lichter and Goodall 1989). Crespo and Corcuera (1990) also refer to catches in bottom and midwater trawls in Chubut, and a midwater trawl fishery in Santa Cruz province of Argentina.

Phocoena spinipinnis Burmeister's porpoise
About 10–15 Burmeister's porpoises are reported taken annually in shark nets set at around 50m off Necochea (Monzon et al 1990). Some are also evidently taken in set nets in Tierra del Fuego (1 reported in 1987/8: Lichter and Goodall 1989), and in coastal gillnets around Buenos Aires (8 reported in 3 years by Goodall, Galeazzi and Lichter 1988). In Uruguay, Praderi (1990) refers to captures of 8 Burmeister's porpoises in shark gillnets since 1974.

Australophocoena dioptrica Spectacled porpoise.
Lichter and Goodall (1989) report 6 spectacled porpoises which ‘probably’ died in nets, presumably gill or tangle nets, in Tierra del Fuego in 1987/8. Crespo and Corcuera (1990) refer to catches of this species in trawls in Chubut and in Santa Cruz in Argentina. Numbers caught are not known.

Inia geoffrensis Boto
Best and da Silva (1989) report on accidental catches of the boto in the Amazon. Total catches are unknown, but are thought to have increased with increased fishing effort. The overall impression was that, in 1984, incidental catches had not yet reached excessive proportions. Lampara seine nets and gillnets are most frequently responsible for incidental captures.

Pontoporia blainvillei Franciscana.
The franciscana is caught in fairly large numbers in gillnets set for sharks along most of its coastal range. Shark fishing in Uruguay started in 1942, and catches of franciscana have been estimated there at an average of 279 per year between 1974 and 1978, and 134 per year between 1978 and 1981. Praderi (1990) states that between 1974 and 1990 over 3000 Franciscanas were taken in Uruguayan shark fisheries. There has been a decreasing trend in fishing effort in this fishery in recent years. Between 1976 and 1985 a total of 723 franciscana have been recovered from a 120 km section of beach in southern Brazil, most of which had died in gillnets (Pinedo et al 1989). Perez Macri and Crespo (1989) report on accidental catches in Argentina and gave an estimate of 340– 350 franciscana deaths per year, mainly in gillnets, but also in other fishing gears. Population sizes are unknown.

Otaria flavescens South American sea lion
Scialabba (1989) reports catches in Uruguay and Argentina in shark nets and trawls, but no estimates of numbers were available. Crespo and Corcuera (1990) report that sea lions damage gillnets in the Necochea and Clarameco shark fishery. Up to 60% of the catch may be damaged. The same authors also refer to catches in Chubut in a trawl fishery.

Arctocephalus australis South American fur seal
Scialabba (1989) also reports catches in Uruguay and Argentina in shark nets and trawls, but no estimates of numbers for this species were available either. Observer reports from trawlers in the Falkland Islands indicate that fur seals are quite often seen near to fishing operations, but in 4 years only 1 record of a fur seal having drowned has been received.

Species in this area for which no recent information on interactions with fisheries has been found include: Eubalaena australis, Caperea marginata, Balaenoptera physalus, B. musculus, B. acutorostrata, B. borealis, B. edeni, Tasmacetus shepherdi, Berardius arnuxii, Mesoplodon layardii, M. hectori, M grayi, Ziphius cavirostris, Hyperoodon planifrons, Kogia breviceps, Kogia simus, Steno bredanensis, Orcinus orca, Globicephala macrorhynchyus, Lagenorhynchus cruciger, Grampus griseus, Stenella longirostris, Stenella coeruleoalba, S. attenuata, S. frontalis, Cephalorhynchus eutropia, Mirounga leonina, Leptonychotes weddelli, Trichechus inunguis.

Area 41 Summary

The large number of species present and the wide range of geographical zones encompassed by this area make generalisations difficult. The major interactions involve the smaller species. Franciscanas appear to be particularly heavily impacted, but the population size and effect of catches in shark nets are unknown. Commerson's dolphins are also reportedly caught quite frequently in Argentina, but again the impact on populations is not known.

The major fisheries involved in incidental catches in this area are the shark gillnet and other inshore gillnet fisheries. Trawls and seines also take a proportion of cetaceans, but apparently to a lesser extent than gillnets.

Area 47 Southeast Atlantic

Cephalorhynchus heavisidii Heaviside's dolphin
Cockcroft (1990) refers to an inshore set gillnet fishery in Namibia suspected of entangling unknown numbers of this species, which is confined to this area.

Arctocephalus pusillus South African fur seal.
The diet of the South African fur seal was studied by David (1987), who found that Cape hakes, anchovy, horse mackerel, pelagic goby and pilchards were all consumed in large proportions, although the diet composition was found to vary between locations. Following a commission of enquiry, the South African government decided that the fur seal population needed to be culled to limit competition with fisheries. This decision was criticised by Butterworth et al (1988) who pointed out that there was no scientific basis for such a decision; the proposed cull was not carried out, but a licensed commercial seal kill has been proposed. The debate on the potential impact of this fur seal population on South Africa's fisheries continues in 1991, with a proposed symposium on the subject.

No other specific information on marine mammal fishery interactions for the last few years could be found for this area. There is a large number of species present in the waters of this area, and several have previously been reported to be subject to incidental capture. The species present include: Eubalaena australis, Caperea marginata, Balaenoptera physalus, B. musculus, B. acutorostrata, B. borealis, B. edeni, Megaptera novaeangliae, Berardius arnuxii, Mesoplodon densirostris, M. layardii, M. hectori, M. grayi, M. mirus, Z. cavirostris, Hyperoodon planifrons, Physeter macrocephalus, Kogia breviceps, K. simus, Steno bredanensis, Sousa plumbea, S. teuszii, Peponocephala electra, Feresa attenuata, Pseudorca crassidens, Orcinus orca, Globicephala melaena, G. macrorhynchus, Lagenorhynchus obscurus, L. cruciger, Lagenodelphis hosei, Tursiops truncatus, Grampus griseus, Stenella longirostris, S. coeruleoalba, S. attenuata, Delphinus delphis, Lissodelphis peronii, Arctocephalus tropicalis, Trichechus senegalensis.

Summary Area 41

Few recent studies appear to have been made in this area. The recent revelation (Ryan and Cooper, 1991) that a driftnet fishery has been operating off Tristan da Cunha for tunas, with a concomitant incidental kill of small whales and dolphins suggests that there may be a considerable mortality to some, as yet unidentified, species. Incidental mortality to Heaviside's dolphin which is restricted to the coastal zone of South Africa and Namibia may also be an important interaction, but recent data on catches and data on population size are lacking.

The fisheries of prime concern are the driftnet fishery for tuna, and any coastal fisheries which may impact Heaviside's dolphin. Neither of these is documented. The possible competition between fur seals and South African fisheries is also evidently an issue of concern, which remains to be resolved.

Area 51 Eastern Indian Ocean

Balaenoptera physalus Fin whale.
One fin whale is reported to have been taken in the Sri Lankan driftnet fishery in 1985 (Leatherwood and Reeves 1990).

Physeter macrocephalus Sperm whale.
Two sperm whales were reported taken in 1982 in the Sri Lankan driftnet fishery (Joseph et al 1983).

Kogia breviceps Pygmy sperm whale.
Pygmy sperm whales are one of the major small whale species taken in the Sri Lankan driftnet fisheries. Up to 6% of the landed catch consists of this species (Dayaratne and de Silva 1990), and as the total annual catch for all species has been estimated at around 15000 to 25000, total annual catches may reach 2700 animals. No data are available on population size or impact of this catch.

Kogia simus Dwarf sperm whale.
Also present as up to 6% of total cetaceans landings (Dayaratne and de Silva 1990), a similar total catch of dwarf sperm whales might be expected; again, there are no population estimates or indications of impacts on the local population.

Steno bredanensis Rough-toothed dolphin
This dolphin occurs in the Sri Lankan driftnet fishery in small numbers only, (5 recorded in total) with a maximum of only 2% in one sample (Dayaratne and de Silva 1990), suggesting a catch of perhaps some hundreds per year. No information on population size or impact of this catch level are available, but this is not a common species worldwide.

Sousa chinensis Indopacific hump-backed dolphin.
Cockcroft (1990) review catches of this species in the Natal shark nets. 67 individuals have been recorded between 1980 and 1988. Peddemors (1990) states that local stocks are possibly threatened by this catch, among other pressures, which amounts to around 5% of the local population. Hump-backed dolphins are also taken in Indian coastal fisheries, in unknown numbers, with an average of 2.2 animals recorded per year by Lal Mohan (1985) in the Calicut gillnet fishery. Elsewhere, Lal Mohan (1990) states that this species, among others, is commonly entangled in coastal driftnet fisheries for seerfish and tunas on the Indian west coast, and is also entangled in set nets and driftnets for pomfrets. Cockcroft (1990a) refers to anecdotal accounts of this species being entangled in gillnets in Madagascar. Niazi (1990) refers to entanglement in medium and large mesh gillnets in offshore waters of Pakistan.

Peponocephala electra Melon-headed whale.
Three melon-headed whales have been reported taken in the Sri Lankan driftnet fishery (Leatherwood and Reeves 1990)

Feresa attenuata Pygmy killer whale
Pygmy killer whales have been recorded in the Sri Lankan driftnet fishery, where they have made up to 4% of the catch in one sample. Population size and impacts of the fishery are not known.

Pseudorca crassidens False killer whale
1 animal has been taken in the Natal shark nets between 1980 and 1988 (Cockcroft 1990). Lal Mohan (1985) also refers to the capture of this species in Calicut, India; catches in the Sri Lankan fishery of up to 6% of one sample have been recorded (Dayaratne and de Silva 1990).

Lagenodelphis hosei Fraser's dolphin
Two Fraser's dolphins have been recorded in the Natal shark nets (Cockcroft 1990), while only one individual was reported in the Sri Lankan driftnet fishery (Dayaratne and de Silva 1990).

Tursiops truncatus Bottlenose dolphin
Bottlenose dolphins are frequently taken in the Natal shark nets, where 271 have been recorded in the space of 9 years (Cockcroft 1990). Peddemors (1990) suggested that current catch rates may approach 5% of the local population and therefore may threaten it. Catches in India are reported quite frequently, and formed 33% of the total catch of cetaceans recorded in the gillnet fishery at Calicut (Lal Mohan 1985). Lal Mohan (1990) also includes this species as one of those commonly taken in seerfish and tuna driftnet fisheries on the west coast of India, and in coastal gillnet fisheries for pomfrets and other species too. In Sri Lanka, this species was found to consist of between 5 and 25% of the total cetacean catch in four different surveys (Dayaratne and de Silva 1990), where the total catch of all cetaceans may be from 25000 to 45000 (Leatherwood and Reeves 1990). Cockcroft (1990a) refers to anecdotal accounts of incidental entanglement of bottlenose dolphins in gillnets in Madagascar. Niazi (1990) refers to unquantified entanglements in medium and large mesh gillnets in offshore waters of Pakistan.

Grampus griseus Risso's dolphin.
Risso's dolphin is taken quite frequently in the Sri Lankan fishery (between 6% and 16% of the total cetacean catch - Dayaratne and de Silva 1990). No populations estimates or information on the impact of this catch are available.

Stenella longirostris Spinner dolphin.
Spinner dolphins are the most frequently caught species in the Sri Lankan fishery, where they formed between 33 and 47% of the total cetacean catch in for different surveys (Dayaratne and de Silva 1990). Total catches may be expected to be numbered well into the thousands per year, but the impact of this level of catch on local populations is unknown. A single animal is reported from the Natal shark nets (Cockcroft 1990), while in India, Lal Mohan (1985) found that it made up more than 50% of the cetacean catch he examined from a gillnet fishery. Niazi (1990) reports that this species is taken in Pakistani offshore deepwater gillnet fisheries. Lal Mohan (1990) states that this species among others is commonly entangled in coastal driftnet fisheries for seerfish and tunas on the west coast of India, and is also taken in other gillnet fisheries for sharks, pomfrets and other species.

Stenella coeruleoalba Striped dolphin.
Striped dolphins are frequently taken in the Sri Lankan driftnet fishery where between 6 and 11% of all cetaceans landed were found to be this species (Dayaratne and de Silva 1990). Three individuals have also been recorded in the Natal shark nets (Cockcroft 1990). Niazi (1990) refers to unquantified catches in the offshore gillnet fisheries of Pakistan.

Stenella attenuata Pantropical spotted dolphin
Up to 27% of all cetaceans landed in Sri Lanka are spotted dolphins (Dayaratne and de Silva 1990), suggesting a total annual catch in the thousands. No information on the level of impact on the population is available.

Delphinus delphis Common dolphin.
Curiously absent from statistics on the Sri Lankan fishery, Lal Mohan (1985) suggests that this species may form around 8% of the total cetacean catches in the Calicut gillnet fishery (14 were recorded in 5 years). It is also known to get entangled in driftnets and bottom set gillnets for pomfrets and other species in Indian (Lal Mohan 1990).

Neophocaena phocaenoides Finless porpoise.
Although a coastal species, there is little information on this species in area 51; it is reported in Indian inshore fisheries, but from whereabouts in India is not recorded (Perrin 1987). Lal Mohan (1990) states that this species amongst others is commonly taken in seerfish and tuna driftnet fisheries throughout the west coast of India, and that seerfish fishing effort has increased in these areas during the 1980's. Niazi (1990) refers to two young finless porpoises taken in a shrimp trawl in Pakistan in 1989, to entanglements in beach seines and stake nets for shrimp, and to entanglements in small and medium mesh finfish gillnets in shallow inshore waters of Pakistan.

Dugong dugon Dugong
Information on dugong catches in Sri Lanka is reviewed by Leatherwood and Reeves (1990); the population size is considered greatly reduced and dugongs are considered in imminent danger of extinction in Sri Lankan waters, due to intentional and accidental captures. Cockcroft (1990a) refers to anecdotal accounts of dugong entanglement in gillnets in Madagascar.

Recent information on interactions with fisheries was not found for the following cetacean species which are known or expected to occur in this region: Eubalaena australis, Caperea marginata, Balaenoptera musculus, B. acutorostrata, B. borealis, B. edeni, Megaptera novaeangliae, Berardius arnuxii, Mesoplodon pacificus, M. densirostris, M. layardii, M. grayi, M. ginkgodens, Ziphius cavirostris, Hyperoodon planifrons, Orcinus orca, Globicephala macrorhynchus, Lagenorhynchus cruciger, Lissodelphis peronii, Australophocoena dioptrica, Platanista minor, Arctocephalus tropicalis.

Area 51 Summary.

The species most heavily impacted by accidental catches appear to be spinner and spotted dolphins, and pygmy and dwarf sperm whales in Sri Lanka, and bottlenose and humpbacked dolphins in Natal. Dugongs are evidently also heavily impacted but this may be more due to hunting. It should be noted, however, that although much information has been collected in recent years on the species composition of the Sri Lankan catch, several species which might have been expected to occur there in the past, have not been found. These include finless porpoises and Irrawaddy dolphins. It is possible that these species may also be heavily impacted in those parts of their range where they remain, but studies are lacking in much of this region. Both Niazi (1990) and Lal Mohan (1990) refer to catches of finless porpoises in coastal fisheries of India and Pakistan.

Lal Mohan (1990) refers to reports of dolphins damaging catch and fishing nets in Indian coastal driftnet fisheries, but the problem has not been studied in any detail.

This area has a very large number of gillnet (set and drift) fisheries, and catches of cetaceans and dugongs might therefore be expected throughout much of the area. The driftnet fisheries of Pakistan, Iran and the Gulf have been very little studied, and the high seas driftnet fishery by Taiwan remains very little known. Clearly all of these fisheries may take marine mammals in large numbers as the Sri Lankan fishery does. The Natal shark net fishery, although small, is also important for local populations of bottlenose and humpbacked dolphins.

Area 57 Western Indian Ocean

Sousa chinensis Indopacific hump-backed dolphin.
Lal Mohan (1990) states that this species is known to become entangled in Indian shark and catfish gillnet fisheries along the east coast of India.

Orcaella brevirostris Irrawaddy river dolphin
Lal Mohan (1990) refers to accounts of this species being taken in the hilsa driftnet fishery in Bangladesh.

Tursiops truncatus Bottlenose dolphin.
This species is reported by Lal Mohan (1990) to be taken in shark and catfish gillnet fisheries in India.

Stenella longirostris Spinner dolphin.
Lal Mohan (1990) also states that this species is taken in shark and catfish gillnet fisheries in Indian waters.

Delphinus delphis Common dolphin.
Common dolphins are also reported by Lal Mohan (1990) in Indian catfish and shark gillnet fisheries.

Neophocaena phocaenoides Finless porpoise.
This species is also reported taken in unknown numbers in Indian shark and catfish coastal gillnet fisheries (Lal Mohan 1990).

Platanista gangetica Ganges river dolphin.
Lal Mohan (1989) and Shrestha (1989) both report accidental catches of this species as factors affecting its abundance, but this does not appear to be as important a factor as deliberate killing. Numbers caught in fishing gear are not known.

Further recent information on marine mammal fishery interactions in Area 57 appears to be absent. A Taiwanese shark and tuna gillnet fishery which operated off Northern Australia, but is now terminated, caught bottlenose dolphins, spinner dolphins, spotted dolphins, humpbacked dolphins and false killer whales, a proportion of them in this area. The fishery was mainly located in Area 71 and is discussed under that section. Other species which are present or though to be present in this area include : Eubalaena australis, Caperea marginata, Balaenoptera physalus, B. musculus, B. acutorostrata, B. borealis, B. edeni, Megaptera novaeangliae, Berardius arnuxii, Mesoplodon pacificus, M. densirostris, M. layardii, M. hectori, M. grayi, M. bowdoini, M. ginkgodens, Ziphius cavirostris, Hyperoodon planifrons, Physeter macrocephalus, Kogia breviceps, K. simus, Steno bredanensis, Peponocephala electra, Feresa attenuata, Orcinus orca, Globicephala melaena, Globicephala macrorhynchus, Lagenorhynchus obscurus, Lagenorhynchus cruciger, Lagenodelphis hosei, Grampus griseus, Stenella coeruleoalba, Lissodelphis peronii, Australophocoena dioptrica, Neophoca cinerea, Arctocephalus pusillus, Arctocephalus forsteri, Mirounga leonina, Hydrurga leptonyx, Leptonychotes weddelli, Dugong dugon.

Area 57 Summary.

Recent information is so sparse that any summary must be based on what might be expected from previous studies and studies in other areas. Certainly, in view of the amount gillnetting in this region, the small coastal species such as the finless porpoise and Irrawaddy dolphin, as well as the dugong might be expected to be impacted to some extent by accidental catches. The driftnet fisheries operating further offshore, in the Bay of Bengal, for example, might be expected to catch spinner and spotted dolphins, at least, and perhaps other species. Driftnet fisheries in the southern Indian Ocean may catch a variety of species such as the spectacled porpoise perhaps, the southern rightwhale dolphin, and common dolphin, for example. All of these fisheries require more detailed information on non-target catches.

Area 61 Northwest Pacific

Eubalaena glacialis Northern right whale.
Kornev (1990) provides data on a stranded right whale which had been entangled in salmon driftnetting.

Balaenoptera edeni Bryde's whale.
Tobayama et al (1990) refer to the incidental capture of a bryde's whale in Japan in 1988. No further details are given.

Balaenoptera acutorostrata Minke whale.
Minke whales have been reported caught in ‘trap nets’ at a rate of around 5 per year for the last 5 years in Japan (Japanese Progress Reports to the IWC, 1986–1990).

Berardius bairdii Baird's beaked whale
At least 2 Baird's beaked whales have been taken incidentally in Japanese trap nets in the past 5 years (IWC 1986–1990).

Ziphius cavirostris Cuvier's beaked whale.
Tobayama et al (1990) refer to the incidental capture of two of these whales in Japan in 1985 and 1986.

Pseudorca crassidens False killer whale.
Two false killer whales were reported taken in Japanese trap nets in 1988 (IWC 1990).

Zhou and Wang (1990) refer to sporadic captures of this species in coastal fisheries of eastern China.

Orcinus orca Killer whale.
Ito (1986) indicates that a killer whale was taken in research salmon driftnets in 1985; presumably some may occur in the commercial fishery on occasion too.

Globicephala macrorhynchus Short-finned pilot whale.
Pilot whales are reported taken in gillnets, primarily Japanese driftnets, at a rate of around 4 per year (1984–1988), and at a slightly lower rate in trap nets (IWC 1986–1990).

Steno bredanensis Rough-toothed dolphin.
Tobayama et al (1990) refer to the capture of one rough-toothed dolphin in an unspecified Japanese fishery in 1985.

Lagenorhynchus obliquidens Pacific white-sided dolphin
Incidental catches of Pacific white-sided dolphins appear sporadically in the Japanese Progress Reports to the IWC. Reported catches in gillnets for example have ranged between 0 and 188 in the past 5 years. This would appear to indicate severe under-reporting from the squid driftnet fishery (discussed under Area 67), in which thousands of this species are thought to be taken annually. Reported catches in trap nets have also fluctuated, but to a much smaller degree, with a mean reported catch rate of about 4 per year over the past 5 years.

Tursiops truncatus Bottlenose dolphin.
Still apparently subjected to periodic drive fishing in Japan, incidental catches in that country have been reported at the rate of around 6 per year in a variety of gear types (IWC 1986–90).

Grampus griseus Risso's dolphin
About 2 Risso's dolphins per year are reported taken in fishing gear in Japan (IWC 1986– 90).

Stenella longirostris Spinner dolphin
11 animals were reported taken in Japanese gillnets in 1985 (IWC 1987)

Stenella coeruleoalba Striped dolphin
Reported catches of striped dolphins in Japanese fishing gear have shown an increasing trend over the past five years, rising from 4 in 1984 to 186 in 1988. Most of these were reported in driftnets, presumably the Japanese large mesh or squid driftnet fisheries. Some are also evidently taken in trap nets and other types of gear.

Delphinus delphis Common dolphin
Common dolphins are reported taken by Japanese vessels at a rate of around 20 per year, mainly in gillnets (IWC 1986–90). Catches are known to occur at a higher rate than this in the squid driftnet fishery, so presumably not all are reported.

Lissodelphis borealis Northern rightwhale dolphin.
Reports of northern rightwhale dolphin accidental mortalities have increased since 1984, notably in gillnet fisheries, from 8 to 268 in 1988. About 2 more per year are reported in trapnet fisheries (IWC 1986–90). Catches in the squid driftnet fishery are known to be very much higher than this, and are discussed under Area 67, where most of the squid driftnet fishery is distributed.

Phocoenoides dalli Dall's porpoise.
Dall's porpoise is the main non-target species taken in both the Japanese landbased and mothership salmon driftnet fisheries. Total catches in these two fisheries have been estimated to be around 3000 per year currently (Jones 1990), after a considerable cut-back in fishing effort in the two fisheries. The mothership fishery has been in operation since at least 1952, and catches of over 20000 per year may have occurred in earlier years.

The impact on Dall's porpoise stocks is not clear, because this is a difficult species to survey (it is attracted to boats) and because stock identities have not been clear. The Bering Sea population is estimated to have been reduced to somewhere between 78% and 94% of its pre-exploitation size, and the Western Pacific population to between 66% and 91% of its original size.

Phocoena phocoena Harbour porpoise
Harbour porpoises are reported to be taken in Japanese trap net fisheries fairly frequently, at a rate of around 20–30 per year, and in 1988 71 were also reported taken in gillnets (IWC 1986–90). Harbour porpoises are also taken in the salmon driftnet fishery at a much lower rate than Dall's porpoise, possibly in the tens of animals per year. The impact of these captures on local populations is unknown.

Neophocaena phocaenoides Finless porpoise
This species is sporadically reported caught in Japanese fisheries, presumably coastal fisheries; 14 were reported taken in trap nets in 1987 for example (IWC 1989). Zhou and Wang (1990) refer to numerous reported captures of finless porpoises in Chinese coastal driftnets and stow nets. These authors state that driftnets are one of the factors which have contributed to the decline of this species in the Yangtze river and that dozens if not hundreds drown annually in coastal fishing nets in Jiangsu province. Records are also reported from the Bohai Sea and the East China Sea.

Lipotes vexillifer Baiji
Peixun and Yuanyu (1988) estimate the total population size to be around 300 animals. 45.5% of known deaths of this animal have been caused by accidental catches on longlines which are intensively used in the winter throughout much of the Baiji's range. Interactions with fisheries appear to be a major threat to the survival of this species.

Eumatopias jubatus Northern sea lion.
Burkanov (1990) refers to catches of sea lions by Soviet trawlers in the Bering Sea, and adds that salmon fishermen shoot some sea lions to prevent damage to their catch.

Callorhinus ursinus Northern fur seal
Fur seals have been reported taken in salmon driftnets by research vessels (Ito 1986), and O'Hara et al (1986) estimated that around 600–1000 might be taken in the commercial fishery annually. Burkanov (1990) refers to captures of fur seals by Soviet trawlers in the Bering Sea, but quantitative data are lacking.

Phoca vitulina Common seal
The Kuril seal (P.v. stejnegeri) is reported to be taken in salmon trap nets in the Nemuro peninsular at a rate of about 200 per year (Wada et al 1986). The population is limited to around 300–350 in Hokkaido and perhaps 2400 in the Kuril Islands (Itoo 1986), having been exterminated in other areas of Japan.

Phoca largha Largha seal.
This species is reportedly killed by Soviet salmon fishermen due to predation on salmon in nets, and further, accidental, mortalities are associated with crab trap-net fisheries (Burkanov 1990).

Other species, for which no recent information has been found, but which might be expected to occur in this region include: Balaena mysticetus, Eschrichtius robustus, Balaenoptera physalus, B. musculus, B. borealis, Megaptera novaeangliae, Mesoplodon densirostris, M. stejnegeri, M. bowdoini, M. ginkgodens, M. carlhubbsi, Physeter macrocephalus, Kogia breviceps, Kogia simus, Monodon monoceros, Delphinapterus leucas, Sousa chinensis, Peponocephala electra, Feresa attenuata, Lagenodelphis hosei, Stenella attenuata, Odobenus rosmarus, Phoca hispida, Phoca fasciata, Erignathus barbatus.

Area 61 Summary

Most of the information in this section has been derived from information relating to incidental captures in Japanese fisheries, together with largely anecdotal accounts from Chinese and Soviet fisheries. Clearly accidental catches in Vietnamese, Korean, and Taiwanese fisheries would also be expected, but little information on this subject is available. Furthermore, the figures available for Japan might be taken to suggest some accuracy and reliability in estimating total catches, whereas it is clear that these reported catches are minimum estimates.

The most severely impacted species in this region is clearly the Baiji, but others such as the Kuril seal may also be heavily impacted by fisheries. Dall's porpoise is reported caught most frequently, but this does not necessarily mean that is has been as heavily impacted as some other less well reported species. In Chinese waters the finless porpoise also appears to have been heavily impacted by gillnet fisheries in some areas at least.

Numerically, the major fisheries which interact with marine mammals are reported to be the salmon driftnet fishery (and the squid driftnet fishery which is largely concentrated in area 67). There are, however, a very diverse range of other fisheries in this area, most of which are not reported on, so that it would be difficult to state categorically that these two driftnet fisheries take most marine mammals. Operational damage caused by several pinniped species is evident in Soviet and Japanese salmon fisheries.

Area 67 Northeast Pacific

Eschrichtius robustus Grey whale.
Mate (1985) reports on grey whale entanglements on the Oregon coast; about 2 animals a year become entangled in crab pot lines, but mortality rates from this cause are unknown. Mate also reports two incidents where grey whales were found entangled in salmon gillnets; one of the animals died. O'Hara et al (1986) report that grey whales are prone to entanglement in Alaskan salmon gillnet fisheries, but specific records were not given. Barlow et al (1990) refer to grey whale entanglement in salmon driftnets in British Columbia, and in the Kodiak and Alaska Peninsula salmon gillnet fisheries. Reports of grey whale mortality in these fisheries, however, are rare.

Balaenoptera acutorostrata Minke whale.
Barlow et at (1990) refer to a single minke whale entanglement in the Washington native American gillnet fishery for salmon.

Megaptera novaeangliae Humpback whale.
Humpback whales are occasionally reported in Alaskan salmon gillnet fisheries. Barlow et al (1990) include records of 17 entanglements in fishing gear in southeast Alaska: 8 in gillnets, 4 in longlines or buoy lines, and 5 in unidentified gears, since 1984. Further entanglements are reported by these authors in salmon fisheries in Prince William Sound and in British Columbia. Mortalities as an immediate result of these entanglements appear to be rare.

Delphinapterus leucas White whale.
Melteff and Rosenberg (1984 cited in O'Hara et al 1986) report a minimum of 12 white whale deaths in salmon gillnets in Alaska in 1983. Barlow et al (1990) state that white whales become entangled in Cook Inlet and Bristol Bay salmon gillnet fisheries, at a rate of 10–20 drowned per year in the latter area.

Orcinus orca Killer whale
Killer whales in Alaska are reported to remove catch from sablefish longline fisheries in the southeastern Bering Sea and Prince William Sound areas. Damage may run to thousands of dollars per day, with predation occurring on up to 20% of sets (Dahlheim 1988). Fishermen are reported to retaliate by shooting killer whales, with a resultant significant increase in mortality in some pods (O'Hara et al 1986). Barlow et al (1990) refer to occasional entanglement of killer whales in British Columbia and Prince William Sound salmon gillnet fisheries, and also refer to records of capture in Alaskan trawl fisheries. The numbers involved appear to be very small.

Lagenorhynchus obliquidens Pacific white-sided dolphin.
Pacific white-sided dolphins are reported taken frequently in the high squid driftnet fishery. Results from the 1989 Joint Observer Program indicated an observed catch rate on a sample of vessels which, if extrapolated, might suggest a total catch of perhaps 10000 animals or more. The impact of this level of catch on the population is unknown. Further catches are reported on a smaller scale in both the Alaska trawl fisheries and British Columbia driftnet fisheries for salmon (Barlow et al 1990).

Delphinus delphis Common dolphin
Common dolphins are also taken, to a lesser extent, in the squid driftnet fishery; observer results suggest a few hundred a year may be killed. The impact on populations is unknown.

Lissodelphis borealis Northern right whale dolphin
This species is taken frequently in the squid driftnet fishery, and observer reports indicate catch rates which suggest a total catch of nearly 20000 animals in 1989. The effect on population size is not known.

Phocoenoides dalli Dall's porpoise
Observer reports from the squid driftnet fishery indicate catch rates which would suggest a total catch in 1989 in excess of 5000 animals. The impact of such a catch on any local population is not known. Further catches are referred to by Barlow et al (1990) in salmon gillnet fisheries in British Columbia, Southeast Alaska, Prince William Sound and the Alaskan Peninsula, as well as the Alaskan trawl fishery. No estimates of total catch in these fisheries is available.

Phocoena phocoena Harbour porpoise.
Barlow et al (1990) review information on entanglement of this species in salmon gillnet fisheries in Washington State, British Columbia, Southeast Alaska, Prince William Sound, Cook Inlet, the Alaska Peninsula, Bristol Bay and northern Alaska; catch rates are not well documented, and impacts on local populations are not known. Infrequent catches were also reported in Alaskan trawl fisheries. As elsewhere in its range, the harbour porpoise appears to be widely affected by interactions with fisheries.

Eumatopias jubatus Northern Sea lion
Loughlin et al (1990) have reported that northern sea lion numbers continue to decline sharply, by 63% in their study area in the Gulf of Alaska and Aleutian Islands between 1985 and 1989, to around 25000 animals. The causes of this decline are unknown. Loughlin and Nelson (1986) noted a high incidental catch in a joint venture trawl fishery for walleye pollock in this area. They estimated that mortalities in this fishery probably exceeded 1400 in 1982 and subsequently declined to around 350 by 1984, possibly due to changes in the fishery. There is a further catch of sea lions in foreign trawl fisheries in this area, which may amount to around 200 sea lions per year (O'Hara et al 1986). Catches in domestic fisheries have not been documented. Loughlin and Merrick (1988) found some correlations between increasing amounts of fish caught and decreasing sea lion numbers in some areas, but such trends were not consistently observed over the whole range.

Zalophus californianus California Sea Lion
California sea lions are reported to cause some minor damage to a herring fishery in Yaquina Bay, Oregon (Brown 1988).

Callorhinus ursinus Northern fur seal.
Northern fur seals are also taken in the squid driftnet fishery. Observer reports in 1989 indicate catch rates suggesting total catches of over 8000, at least two thirds of which may have escaped alive. Catches in trawl fisheries continue at a low level (O'Hara et al 1986).

Phoca vitulina Harbour seal
O'Hara et al (1986) report that about 350 harbour seals are killed in gillnets in the Columbia River annually; considerable damage is also done to fishing gear. There is some additional unquantified mortality in sturgeon nets in the Columbia river too (Brown 1988). Harbour seal population numbers in this latter area continue to increase by around 6–8% per year (Brown 1988). In much of the southeastern Bering Sea, central Gulf of Alaska and in Prince William Sound, harbour seal numbers have declined in recent years (Pitcher 1989). The reasons for this are not known, but interactions with fisheries have been suggested as one possible cause (Pitcher 1989). Barlow et al (1990) refer to harbour seal mortalities in Alaskan trawl fisheries, and Washington State and Prince William Sound salmon gillnet fisheries. Reported entanglements, however, have not been vary numerous.

Most of the marine mammals in this area have been reported to interact with fisheries to some extent, especially the pinnipeds. Recent studies of interactions with fisheries could not be located for the remaining species likely to be found in this area. These include : Eubalaena glacialis, Balaena mysticetus, Balaenoptera physalus, B. musculus, B. borealis, Berardius bairdii, Mesoplodon stejnegeri, M. carlhubbsi, Z. cavirostris, Physeter macrocephalus, Monodon monoceros, Delphinapterus leucas, Orcinus orca, Globicephala macrorhynchus, Grampus griseus, Stenella coeruleoalba, Odobenus rosmarus, Phoca largha, Phoca hispida, Phoca fasciata, Erignathus barbatus, Mirounga angustirostris.

Area 67 Summary

The main species affected by incidental capture in this area include the northern right whale dolphin and Pacific white-sided dolphin, in the squid fishery, but harbour seals and northern fur seals may be taken in large enough numbers that incidental catches are partly responsible for their population declines in Alaska; mortalities in domestic fisheries are poorly known.

The major fisheries involved in interactions are the squid driftnet fishery, inshore salmon gillnet fisheries, and the Alaska pollock fishery, which, it has been suggested, may be partly responsible, by decreasing fish abundance, for declines in sea lion numbers.

Competition between marine mammals and fisheries is everywhere difficult to demonstrate, but a reduction in food supply due to fishing seems a plausible partial explanation for declines in certain species is Alaska.

Area 71 Western Central Pacific

Sousa chinensis Indopacific hump-backed dolphin
One animal was reported in a Taiwanese driftnet fishery for spanish mackerel, tunas and sharks operating off northern Australia between 1974 and 1986 (Harwood and Hembree 1987).

Pseudorca crassidens False killer whale
A single animal is reported by Harwood and Hembree (1987) in the Taiwanese driftnet fishery off Northern Australia.

Tursiops truncatus Bottlenose dolphin
This species formed about 60% of the total identified cetacean catch in the Taiwanese tuna, shark and spanish mackerel driftnet fishery off Northern Australia. The total catch from June 1981 to December 1985 was estimated to be around 14000 cetaceans, suggesting at least 8400 bottlenose dolphins had been caught during this period (Harwood and Hembree 1987). This was judged to be impacting local populations severely, and the fishery was closed in 1986.

Stenella longirostris Spinner dolphin
Spinner dolphins made up some 35% of the identified cetaceans in the catch of the Taiwanese driftnet fishery in Northern Australian waters, suggesting a total removal of at least 4900 spinner dolphins over a period of 54 months (Harwood and Hembree 1987). A newly described dwarf form of this species from the Gulf of Thailand was identified on the basis of ten specimens taken in shrimp trawls in the Gulf of Thailand in 1970/71 (Perrin et al 1989). Dolar (1990) refers to this as one of the three species reportedly taken in purse seine and driftnet fisheries in the Visayan Sea in the Philippines. Total annual mortalities for all three species were thought to number around 2000 and 20 dolphins in the purse seine and driftnet fisheries respectively.

Stenella attenuata Pantropical spotted dolphin
This species formed 4.5% of identified cetaceans in the Taiwanese gillnet fishery (Harwood and Hembree 1987). This was also one of three species taken in two purse seine fisheries and a smaller driftnet fishery (for clupeids and needlefish) in the Visayan Sea in the Philippines reported by Dolar (1990). Total annual mortalities for the three species may amount to more than 2000 individuals in these three fisheries.

Lagenodelphis hosei Fraser's dolphin.
Reported to be taken along with two other species in two purse seine fisheries and a small driftnet fishery in the Visayan Sea in the Philippines. Total annual mortalities of all three species may exceed 2000 (Dolar 1990).

Other species, for which no recent information on interactions with fisheries was found, but which might be expected to be found in this area include: Balaenoptera physalus, B. musculus, B. acutorostrata, B. borealis, B. edeni, M. novaeangliae, M. pacificus, M. densirostris, M. layardii, M. bowdoini, M. ginkgodens, Ziphius cavirostris, Physeter macrocephalus, Kogia breviceps, Kogia simus, Steno bredanensis Sousa chinensis, Orcaella brevirostris, Peponocephala electra, Feresa attenuata, Orcinus orca, Globicephala macrorhynchus, Grampus griseus, Stenella coeruleoalba, Delphinus delphis, Neophocaena phocaenoides, Dugong dugon.

Area 71 Summary

The bottlenose dolphin is clearly the most heavily impacted species of those which have been studied recently, but this is an area where there is very heavy coastal gillnetting, and several other species might therefore also be at risk. These would include for example, Irrawaddy dolphins and finless porpoises. Little is known of the status of these species, and almost nothing about their interaction with fisheries.

The fisheries of this region are diverse and little documented. It is clear however, that coastal gillnets, especially driftnets for tunas and mackerels are widely used. After closure in Australian waters, the Taiwanese driftnet fishery referred to above has continued fishing in Indonesian waters, in the Arafura Sea. Total fishing effort in 1987 in the Arafura Sea was similar to the combined effort for the years 1981 to 1985 in Australian waters, and consequently a high cetacean catch rate might be expected here (Northridge 1991). The extent of any possible competition between marine mammals and fisheries is unknown.

Area 77 Eastern Central Pacific

Eschrichtius robustus Grey whale
This whale is regularly entangled in low numbers in Californian gillnet fisheries. Heyning and Lewis (1990) provide 61 records of grey whale entanglements in the Californian swordfish and shark driftnet fishery and inshore set net fisheries between 1981 and 1989. These records were based on evidence from stranded animals and from sightings at sea. Approximately a third of the records involved dead animals. The inshore set net fisheries were considered to account for most grey whale entanglements. These fisheries have been excluded from shallow water areas since 1985 and entanglement rates may have declined subsequently. The authors report that most entangled grey whales are young animals (3 years old or less) and that the level of entanglement currently observed does not appear to have affected the population size in any significant way.

Balaenoptera acutorostrata Minke whale
Diamond et al (1987) report two minke whales entangled in California swordfish driftnets, in 1984 and 1985; one was released alive. Heyning and Lewis (1990) provide 2 additional records, from 1983 and 1988, and on the basis of anecdotal information from driftnet fishermen, suggest that minke whale entanglements may be more frequent than previously thought.

Megaptera novaeangliae Humpback whales.

Heyning and Lewis (1990) record two humpback whales entangled in Californian gillnets (in 1984). Numbers killed in the shark and swordfish driftnet fishery are unknown, but these authors warn that, in view of the size of the population in this area (1000+ animals), any increase in driftnetting could cause a significant problem.

Mesoplodon carlhubbsi Hubb's beaked whale.
Two beaked whales, probably this species, were observed taken in Californian driftnets in 1985 (Diamond et al 1987), and one stranded individual with net marks was observed in 1986 (Heyning et al 1990).

Steno bredanensis Rough-toothed dolphin.
Taken in small numbers in the tuna purse seine fishery, 16 mortalities were recorded in 1989 in this fishery (Hall and Boyer 1990).

Orcinus orca Killer whale.
Heyning et al (1990) refer to one beached killer whale which was found in southern California in 1985, and which bore evidence of having been entangled.

Globicephala macrorhynchus Short-finned pilot whale.
Pilot whales are also taken in small number in the tuna purse seine fishery. 1 was recorded in 1989 (Hall and Boyer 1990), and Heyning et al (1990) refer to an individual found dead at San Clemente Island, California, which was presumed to have been accidentally taken in fishing gear, in 1988.

Grampus griseus Risso's dolphin.
Heyning et al (1990) record 4 beached animals which were suspected of having died in purse seine operations for squid in 1988 and 1989 in southern California.

Lagenorhynchus obliquidens Pacific white-sided dolphin
45 were reported taken in the tuna purse seine fishery in 1989 (Hall and Boyer 1990). Heyning et al (1990) record two beached animals found in southern California in 1988, which were thought to have died in fishing gear.

Lagenodelphis hosei Fraser's dolphin
Two individuals were recorded taken in the tuna purse seine fishery in 1989 (Hall and Boyer 1990).

Tursiops truncatus Bottlenose dolphin
Taken in relatively small numbers in the tuna purse seine fishery, 145 were reported in 1989 (Hall and Boyer 1990). Heyning et al (1990) refer to a beached animal in southern California in 1988 which was presumed to have died in fishing operations.

Stenella longirostris Spinner dolphin
Spinner dolphins are taken in large numbers by the tuna purse seine fishery in the eastern tropical Pacific. About 22000, from 3 stocks, were estimated to have been caught in 1989 (Hall and Boyer 1990). There are estimated to be around 2.5 million spinner dolphins in the eastern tropical Pacific (ETP) (Gerrodette and Wade 1990).

Stenella coeruleoalba Striped dolphin
179 striped dolphins were taken in the ETP tuna purse seine fishery in 1989 (Hall and Boyer 1990); estimates of population size (4 stocks) total around 1.8 million (Gerrodette and Wade 1990).

Stenella attenuata Spotted dolphin.
The most frequently taken species in the ETP tuna purse seine fishery, catches in 1989 were estimated at around 55000 for two stocks with a total estimated population size of 3.6 million (Hall and Boyer 1990, Gerrodette and Wade 1990).

Delphinus delphis Common dolphin
This species is taken in the California swordfish driftnet fishery. 7 individuals were observed taken in 1985 in observations of about 1% of the total driftnetting effort, and 3 were reported in 1984 (Diamond et al 1987). Heyning et al (1990) reported on beached cetaceans in southern California which bore evidence of having been caught in fishing gear. Common dolphins were the most numerous such species (31 individuals or 45%) between 1975 and 1990. Population sizes in southern Californian waters are not known, but this is reportedly the most numerous cetacean species in the area. Common dolphins are more heavily impacted by the tuna purse seine fishery. An estimated 14000 were taken in 1989 (Hall and Boyer 1990) from 3 stocks with a total population size of around 2.5 million in the ETP (Gerrodette and Wade 1990).

Lissodelphis borealis Northern right whale dolphin
1 individual was observed in 1985 in the driftnet fishery in California in 1985 (Diamond et al 1987).

Phocoena phocoena Harbour porpoise
Henry (1986) observed two harbour porpoises taken in 18 km of gillnetting set in inshore waters of central California in 5 months in 1985. Hanan et al (1987) estimated harbour porpoise mortalities in central Californian set gillnet fisheries for California halibut as 226 individuals in 1985–86, which compared with an estimate of 226 in 1984–85 and 303 in 1983–84. Barlow (1987) estimated the California harbour porpoise population size (central estimate of 1854) and suggested that harbour porpoise abundance in central California is approximately 21–81% of that in 1969.

Phocoena sinus Vaquita
Vidal (1990) has reviewed information on this species. At least 110 have been reported caught in a variety of gillnets (mainly totoaba gillnets) and shrimp trawls since the early 1970's. The population size is not known but is considered very small, and catches in fishing gear are considered a threat to the survival of this species.

Zalophus californianus California sea lion
Some hundreds of California sea lions are taken every year in the driftnet fishery for swordfish (Diamond et al 1987). A further 2–4000 may be taken annually in the inshore gillnet fisheries in California, but the population is still growing in Californian waters (Barlow et al 1990).

Phoca vitulina Harbour seal
Harbour seals are taken in a variety of fisheries in California, mainly gillnet fisheries, with around 1–2000 mortalities a year in the inshore set net fishery; population numbers continue to increase in this area (Barlow et al 1990).

Most of the species recorded in this area have also been reported to interact with fisheries. A summary of information on Californian interactions was given by Miller et al (1983). The species for which no recent information on interactions with fisheries could be found, but which are recorded in this area, include: Eubalaena glacialis, Balaenoptera physalus, Balaenoptera musculus, B. borealis, B. edeni, Berardius bairdii, Mesoplodon densirostris, M. hectori, M. ginkgodens, Ziphius cavirostris, Physeter macrocephalus, Kogia breviceps, K. simus, Peponocephala electra, Feresa attenuata, Pseudorca crassidens, Orcinus orca, Grampus griseus, Phocoenoides dalli, Eumatopias jubatus, Callorhinus ursinus, Arctocephalus townsendi, A. galapagoensis, Monachus schauinslandii, Mirounga angustirostris.

Area 77 Summary.

The species most frequently caught in this area is the spotted dolphin, but more significant are catches of the Vaquita and the harbour porpoise in coastal gillnet fisheries. The vaquita may be threatened with extinction by gillnet fisheries.

The major fisheries are the Eastern Tropical Pacific tuna purse seine fishery which took around 100000 dolphins in 1989. Although catching far fewer cetaceans, inshore gillnet fisheries are also very important for the impact they have on less numerous coastally distributed species. The impact of the Californian swordfish and shark driftnet fishery is less well understood as fewer studies have been made. Investigations by the US National Marine Fisheries Service are currently underway.

Most of the information from this area comes from US waters. Information from Central and South American Pacific waters is largely absent.

Area 81 Southwest Pacific

Hyperoodon ampullatus Southern bottlenose whale.
This species has been reported taken in the large mesh driftnet fishery for albacore in the Tasman Sea (Coffey and Grace 1990). Very little is known of this whale species, and impacts of the driftnet fishery are unknown, but the fishery is due to be terminated in 1991.

Delphinus delphis Common dolphin
Common dolphins were reported quite frequently in the albacore driftnet fishery in the Tasman Sea. Estimates of total catches in this area for 1989/90 were over 4000 (Coffey and Grace 1990). The impact on local populations is unknown, but the fishery is to be closed.

Cephalorhynchus hectori. Hector's dolphin
Hector's dolphin has been taken in bottom set gillnets around New Zealand, and particularly around the Banks Peninsula. The total population has been estimated at around 3000–4000, and incidental captures around the Banks Peninsula amounted to some at least 223 between 1984 and 1988. As a result set netting has been banned in this area (New Zealand 1988).

Phocarctos hookeri Hooker's sea lion
This species is affected by a trawl fishery for squid, around the Auckland Islands. Although only few animals have been reported taken (19 during 1979-1982), the population is relatively small and may total around 6000–7000. Doonan and Cawthorn (1984) conclude that the effect of the fishery on the sea lion population is unclear, but suggest that the fishery may be causing a slow population decline.

Arctocephalus forsteri New Zealand fur seal.
This species is caught in a midwater trawl fishery for hoki off the west coast of South Island. In 1989 47 vessels operated in this fishery and 9 carried scientific observers who recorded 198 fur seals taken in midwater trawls; an additional 6 records were also obtained from other vessels. This catch is somewhat higher than recorded in previous years (MAFF 1990). The impact on local populations is unclear, as population estimates have not been made recently. The total population may be between 30 and 50 thousand.

Most of the species in this area have not been reported to interact with fisheries, at least recently. Other species expected in this area include : Eubalaena australis, Caperea marginata, Balaenoptera physalus, Balaenoptera musculus, B. acutorostrata, B. borealis, B. edeni, M. novaeangliae, Tasmacetus shepherdi, Berardius arnuxii, Mesoplodon densirostris, M. layardii, M. hectori, M. grayi, M. bowdoini, Ziphius cavirostris, Physeter macrocephalus, Kogia breviceps, Pseudorca crassidens, Orcinus orca, Globicephala melaena, Lagenorhynchus obscurus, L. cruciger, Tursiops truncatus, Grampus griseus, Stenella coeruleoalba, Lissodelphis peronii, Australophocoena dioptrica, Arctocephalus pusillus, Mirounga leonina, Hydrurga leptonyx, Leptonychotes weddelli.

Area 81 Summary

The major documented impact in this area has been on Hector's dolphin, but the impact of the driftnet fisheries in this area is unknown, and Hooker's Sea lion has also been impacted by the trawl fishery for squid.

The closure of the driftnet fishery by 1991 will mean that the only remaining fisheries with any recently documented impact on marine mammals will be the midwater trawl fisheries for hoki and squid. Presumably, however, inshore gillnetting away from the Banks Peninsula may also still impact Hector's dolphin and other species.

Area 87 Southeast Pacific

Mesoplodon peruvianus

A recently described addition to the genus Mesoplodon, Reyes et al (1991) record 10 specimens of this species, at least 9 of which appear to have been taken in the Peruvian coastal driftnet fishery. The range and population size of this species are unknown.

Physeter macrocephalus Sperm whale
Brito (pers comm) reports that this species has been taken in swordfish driftnets in Chile; numbers involved are unknown.

Kogia breviceps Pygmy sperm whale.
Van Waerebeek et al (1987) report a specimen from Peru which had apparently been taken by fishermen.

Feresa attenuata Pygmy killer whale.
Van Waerebeek and Reyes (1988) report on a specimen taken in Peruvian coastal gillnets.

Orcinus orca Killer whale.
Brito (pers comm) reports that this species is taken in Chilean driftnets in unknown numbers.

Globicephala macrorhynchus Short finned pilot whale
At least 3 pilot whales have been taken in driftnets in Peru in 1987 (Van Waerebeek and Reyes 1990).

Lagenorhynchus obscurus Dusky dolphin
Van Waerebeek et al (1990) and Read et al (1988) report on large catches of dusky dolphins in Peru and Chile; this fishery, which uses driftnets, is partly directed at dolphins, but also at a range of other fish. Catches at Pucusana were estimated at 711 in 1987. Clearly catches in all of Peru and Chile will be much higher than this. There is no information on population size.

Lagenorhynchus australis Peale's dolphin
This species is reported to be taken for crab bait in southern Chile in unknown numbers (Perrin 1985).

Tursiops truncatus Bottlenose dolphin
Bottlenose dolphins are reported taken in gillnets in Peru; catches at Pucusana were estimated to total 30 in 1987 (Van Waerebeek and Reyes 1990).

Grampus griseus Risso's dolphin
At least one animal is reported to have been landed at Pucusana in Peru (Van Waerebeek and Reyes 1990).

Lissodelphis peronii Southern right whale dolphin
Reported taken occasionally in Tierra del Fuego as crab bait (Perrin 1985). This species is also taken in driftnets in Chile in unknown numbers (Brito pers comm).

Delphinus delphis Common dolphin
Catches of common dolphins in coastal driftnets have been reported in Peru, where Van Waerebeek et al (1990) estimated a catch of 264 in 1987.

Cephalorhynchus eutropia Chilean dolphin
Goodall, Norris et al (1988) review information on catches of this species. Catches are known to occur in a variety of gill and other nets, and some capture for crab bait is also thought to continue. The numbers of animals involved is not known.

Cephalorhynchus commersonii Commerson's dolphin
Goodall, Galeazzi et al (1988) review information on catches of this species. Catches continue in set nets for robalo in Chile, in unknown numbers, and some illegal tangle netting for crabs may also take an unknown number. Perrin (1985) suggests that this is the species most heavily impacted by the crab-bait fishery in this region. Again the numbers taken are unknown.

Phocoena spinipinnis Burmeister's porpoise.
This species is taken in driftnets in Peru, where Van Waerebeek et al (1990) estimated catches of 83 at Pucusana in 1987. Impact on any local populations is unknown. Total catches in Peru are clearly much higher. There are also unquantified catches in Tierra del Fuego, including some for crab bait (Perrin 1985). Catches also occur in the Chilean swordfish driftnet fishery (Brito pers comm).

Other species expected in this area, but for which no recent information has been found, include: Eubalaena glacialis, Caperea marginata, Balaenoptera physalus, Balaenoptera musculus, B. acutorostrata, B. borealis, B. edeni, Megaptera novaeangliae, Tasmacetus shepherdi, Berardius arnuxii, Mesoplodon layardii, Mesoplodon grayi, Ziphius cavirostris, Hyperoodon planifrons, Kogia simus, Pseudorca crassidens, Globicephala melaena, Lagenorhynchus cruciger, Stenella longirostris, Stenella attenuata, Otaria flavescens, Arctocephalus philippii, Arctocephalus australis, Leptonychotes weddelli, Mirounga leonina.

Area 81 Summary.

The dusky dolphin is perhaps the most frequently captured species in this area, but several other species may also be heavily impacted in a variety of fisheries. These include Burmeister's porpoise, the Chilean dolphin, and possibly southern right whale dolphins and Peale's and Commerson's dolphins. Read et al (1988) estimated that around 10000 small cetaceans per year may be taken in Peruvian driftnet fisheries, and most of these are dusky dolphins.

Clearly the most important fisheries are the coastal gillnet fisheries, especially the driftnet fisheries, which operate up the entire coastline of South America, but which, outside of Pucusana in Peru, are little documented. Catches for crab bait may also be important, but recent quantitative information on this is lacking.


Top of Page Next Page