Balaena mysticetus Bowhead whale
Braham (1982) estimates the Beaufort Chukchi and Bering Sea stocks to number around 4000, from an estimated initial population of 18 000. Braham et al (1979) have also estimated that the Beaufort Sea part of this stock numbers around 2 200. In 1981 28 bowhead whales were struck by US Inuit whalers, of these 17 were landed. An unknown proportion of animals which were struck but not landed probably die (IWC 1983 p 142).
Eshrichtius robustus Grey whale
Hershkovitz (1966) states that this species occurs as far north as 72°N. The food is thought to include bottom dwelling invertebrates, but not fish.
Balaenoptera physalus Fin whale
Tomilin (1967) suggests that the diet of this species is mostly crustaceans in the more northerly parts of its range.
Balaenoptera musculus Blue whale
The diet is composed of large crustaceans (Tomilin 1967).
Balaenoptera acutorostrata Minke whale
Occurring up into the ice fields, the diet of this species in high latitudes remains unclear, but could presumably include arctic cod.
Megaptera novaeangliae Humpback whale
Physeter macrocephalus Sperm whale
Monodon monoceros Narwhal
Delphinapterus leucas White whale
Fraker (1980) has estimated the Mackenzie stock, in the Beaufort Sea, of this species as 4 or 7 000 individuals. Around 300 animals are taken by Inuit and Inupiat hunters in this area each year (Fraker 1980). Other data are given in the species account.
Orcinus orca Killer whale
Phocoena phocoena Harbour porpoise
Odobenus rosmarus Walrus
Harwood (1981), citing Fay et al, has pointed out that if the walrus population is near its carrying capacity, and is limited by its food supply, then the development of a clam fishery in northern waters could affect the dynamics of the walrus population. About 6 000 animals are also taken every year for human consumption and dog food.
Phoca vitulina Harbour seal
Phoca largha Largha seal
Phoca hispida Ringed seal
Phoca groenlandica Harp seal
Phoca fasciata Ribbon seal
Erignathus barbatus Bearded seal
Cystophora cristata Hooded seal
Very little is known of the feeding habits or population sizes of marine mammals in the arctic regions of area 18. Presumably pelagic crustaceans are important in the diets of most species.
There do not appear to be any commercial fishing operations in this area. The FAO Year-book of Fishery Statistics (1983) indicates that the total catch of 3 groups of fish, namely flounders, halibuts, soles etc., cods, hakes, haddocks etc. and ‘miscellaneous fish’ was zero for the year 1981.
A number of species of marine mammal are hunted in this area for subsistence purposes.
There is little data on the size of these catches, except for the bowhead and white whales which are mentioned above.
There are no records of interactions between any local or artisanal fisheries and marine mammals.
According to Marquette et al (1982) about 95.8% of all zooplankton and nekton in the Beaufort Sea area are consumed by arctic cod (Eleginus navaga). Presumably therefore this species makes up a considerable part of the predatory biomass of the arctic regions. So far it is only exploited in areas 27 and 61 by the USSR.
Eubalaena glacialis Right whale
Reeves and Mead (1978) have recorded a number of this species becoming entangled in fishing gear. They report one individual tangled in the lines of a lobster pot off New Jersey in 1976, though this was later released. Another was reported entangled in netting at Cape Cod in 1976, and two more historic accounts of whale entanglement are mentioned. They conclude that whilst “there is no evidence to indicate that such entanglement happens often, or that it invariably leads to death or debilitation … it should not be overlooked as a potential hazard to individual whales and therefore as an obstacle to the recovery of this small stock.” The population size is unknown, but the report of the sub-committee on Protected Species and Aboriginal Whaling (IWC 1983) indicates that 59 individuals have been photo-identified. A population in the hundreds might be expected. The same report indicated that faecal analysis showed a diet of copepods.
Balaena mysticetus Bowhead whale
Mitchell and Reeves (1981) suggest two Bowhead Stocks, with approximately 700 in the Hudson Bay area, and 600 in the Davis Strait/Baffin Bay area. These represent 15% and 5% respectively of the estimated initial population sizes of the 2 stocks, before exploitation. There are few fisheries in this area at present, and few opportunities for interaction. The diet does not include any fish species (Tomilin 1967).
Balaenoptera physalus Fin whale
Perkins and Beamish (1979) record the entrapment of one individual of this species in a salmon net off Labrador. The Canadian Progress Reports to the IWC list 7 other such cases of entrapment in gill nets off Newfoundland in 1979, 3 in 1980, l in a herring net and 2 in gill nets, and another 1 in 1981 in a herring net. About half of these appear to have been found dead. As has been noted, fin whales are also known to eat commercial fish such as herring, capelin and arctic cod (Jonsgaard 1966, Tomilin 1967), although so far in area 21 this does not appear to be a problem. The population size may be in the thousands for this area.
Balaenoptera musculus Blue whale
The number of blue whales left in the north west Atlantic is unknown but considered very small, and may not exceed a few hundred. No fish are consumed by this species.
Balaenoptera acutorostrata Minke whale
This species seems to become entangled in fishing gear fairly frequently, and records of such cases may be found in the Progress Reports of Canada in the annual Report of the IWC. In 1981 only 1, dead, individual was recorded from a ‘commercial net’. In 1980 12 were recorded, 10 of which were dead. These were trapped in salmon nets, gill nets, and traps, including salmon traps. 9 entrapments are recorded for 1979. Perkins and Beamish (1979) estimate that an average of 3 minkes a year are caught in fishing gear in New-foundland, with a minimum mortality rate of 0.77 in such cases. They state that most records are from cod traps, with a few from gill nets. The minke whale has already been mentioned as another fish eating whale known to feed on some commercial species, although, as with the fin whale, this does not appear to present a problem at present. Again, the population size in this area is unknown. A figure in the low tens of thousands however may not be too unreasonable.
Balaenoptera borealis Sei whale
The stocks of sei whales in this area are still protected by IWC regulations. Gambell (1977) gives an estimate for the north west Atlantic population of 2 078 based on sightings estimates. Mitchell and Chapman (1977) have identified two separate stocks, with centres of abundance in the Labrador Sea and on the Nova Scotia Shelf. Tag-recapture experiments have yielded estimates for the size of the latter population at between 1 393 and 2 248 whales. The Labrador stock is reported to have a minimum of 965 whales from census data. No interactions are recorded.
Balaenoptera edeni Bryde's whale
Mead (1977) reports the most northerly record of this species on the U.S. Atlantic coast as 37°59'N, which is just inside area 21. The population in this area is likely to be very small, and there are no reports of conflicts with fisheries in area 21.
Megaptera novaeangliae Humpback whale
This species is perhaps the most involved in gear entanglements of al baleen whales in this area, and numerous accounts are given in the Canadian Progress Reports to the IWC, with 33 records in 1981. The 1982 Progress Report indicates a total of 43 humpbacks killed in nets from 1969–1980, with a further 88 having been released alive from nets. Humpbacks are particularly prone to this type of interaction as they feed on the capelin stocks in the waters around Newfoundland (Perkins and Beamish 1979), and the effect of such levels of mortality on the recovery of the humpback population cannot be insignificant. Whitehead (1982) has also put forward one view that the fact that the capelin stocks in that region have been severely overfished may also hinder the recovery of this stock of humpback whales. Perkins and Beamish also noted that most entanglements occurred in cod traps, as well as salmon nets, and that such entanglements were extremely expensive for the fishermen to whom the nets belonged. They state that cod traps in 1978 cost US $7–8 000. The population size of this species in the north west Atlantic has been estimated by sightings and acoustic records to number between 1000 and 1 500 in 1978 (Balcomb and Nicholls 1978) and between 2 300 and 4 100 by Whitehead (1982).
Mesoplodon bidens Sowerby's beaked whale
There are no reported interactions with fisheries, and the population size of all members of this genus remain unknown. Very few individuals of any species have been recorded.
Mesoplodon densirostris Blainville's beaked whale
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Mesoplodon europaeus Gervais' beaked whale
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Mesoplodon mirus True's beaked whale
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Ziphius cavirostris Cuvier's beaked whale
Hershkovitz (1966) states that this species occurs as far north as Rhode Island on the American side of the Atlantic. There are no population estimatess, and no apparent interactions with fisheries. This species feeds on squid.
Hyperoodon ampullatus Northern bottlenose whale
Bengaminsen (1972) provides an account of feeding and distribution. This species was until recently hunted by the Norwegians and Mitchell (1977) has suggested that the population is currently depleted. Preferring deeper waters the bottlenose whale spends the summer in high latitudes, and feeds on squid. Interactions with fisheries seem unlikely at present.
Physeter macrocephalus Sperm whale
Townsend's (1935) maps show some of the densest regions of exploitation of sperm whales in the western central Atlantic south of 40°S; the ‘western’ and ‘southern’ grounds straddle the boundary between area 31 and area 21. The population size in area 21 is unknown, but may be in the low tens of thousands in summer at least. The report of the sub-committee on sperm whales (IWC 1982) gives an estimate of 58 000 for the stock exploited by Icelandic whalers. The development of squid fisheries in area 21 may affect some interaction, operational or biological, with this species, but none are known at present.
Kogia breviceps Pygmy sperm whale
Sergeant and Fisher (1957) record the presence of this species in Canadian waters as one individual. Although strandings are not uncommon on the east coast of the U.S.,it is apparently not common on a world scale. No population estimates are available. There are no recorded interactions with fisheries.
Monodon monoceros Narwhal This species is still hunted in northern Canada, especially around Baffin Island; 406 individuals were taken in 1981 (IWC 1983 p 160). The report of the small cetacean sub-committee (IWC 1981) refers to one estimate of the narwhal population in the Lancaster Sound area being around 20 000. The narwhal also eats a number of commercial species, including Greenland halibut, and some crustacea (Finley and Gibb 1982), although as yet this has led to no apparent conflict.
Delphinapterus leucas White whale
Between 616 and 703 white whales were taken in Canada in 1981 (IWC 1983 pl60). The report of the small cetacean sub-committee (IWC 1982) give an estimates for white whale stocks in the east Canadian arctic of around 9 000 whales. This species also eats some commercial species (see Gurevich 1980), but again no conflict with fishing interests is apparent.
Pseudorca crassidens False killer whale
Although no conflicts have been recorded between this species and fishermen in area 21, conflicts may be noted in other parts of the world notably Japan (see area 61) where this species eats both commercial fish and squid, and damages fish on lines. Accordingly such conflicts cannot be ruled out in the future in other parts of the world.
Orcinus orca Killer whale
This species is also noted for conflicts in other parts of the world, due in part to its fish eating habits (see IWC 1982 pp628 – 629), but as yet no such conflicts have been recorded in area 21. The diet in this area may include harp seals and minke whales (Sergeant and Fisher 1957); there are no population estimates for this species in area 21.
Globicephala melaena Long-finned pilot whale
No longer subject to any commercial hunting in area 21, this species is widespread especially around Newfoundland where it feeds on commercial squid, and to some extent fish, (Sergeant 1962). It has rarely been reported entangled in fishing gear such as traps and gill nets in Newfoundland (see Prog. Rep. Canada, IWC 1982). Interaction seems therefore to be minimal at present, but the presence of squid fisheries in the area could represent another potential interaction as indicated by Mercer's (1975) analysis which linked a decline in the catches of pilot whales with an increase in those of squid.
Lagenorhynchus albirostris White-beaked dolphin
This species is known to feed on herring, cod and other commercial species (Tomilin 1957, Sergeant and Fisher 1957). There are no estimates of population size, but the population, however, is thought to be centered more in area 27. The extent to which commercial fish species are present in the diet suggests that some degree of interaction is likely. Leatherwood and Reeves (1983) state that it is common in spring off Cape Cod, and abundant, at least seasonally, further north.
Lagenorhynchus acutus White-sided dolphin
Katona et al (1978) have found one individual of this species which was presumed to have been killed in a gill net in the Gulf of Maine, and which also had herring, squid and hake remains in its stomach. Gaskin (1983) also states that this species is taken incidentally in the mackerel (set) nets of Cape Cod Bay. Leatherwood and Reeves (1983) suggests that this is another fairly common species, adding that it used to be caught incidentally in the Newfoundland drive fishery for piol whales. There is some possibility of this species competing for food with commercial herring and other fisheries, but as yet this has not been reported.
Tursiops truncatus Bottlenose dolphin
Although this species is frequently reported in fishing nets from around the world there do not appear to be any records of such entanglements in area 21; Sergeant and Fisher (1957) describe it as rare in Canadian waters, but it is more common further south in area 21, where it has supported some commercial fishing (Mitcell 1957). The diet is very varied (Tomilin 1967) and is likely to include some commercial species.
Grampus griseus Risso's dolphin
No population estimates are available for this species. No interactions are known at present, the diet is thought to be confined to squid.
Stenella coeruleoalba Striped dolphin
Hershkovitz (1966) states that it is found from southern Greenland to Argentina. There are no population estimates or interactions with fisheries recorded for this area.
Delphinus delphis Common dolphin
Known to eat small fish including some commercial species, there do not seem to be any by-catches in this area, and no other records of interactions with fisheries. Presumably, however, there is some degree of ‘biological’ interaction, which at present remains obscure.
Phocoena phocoenaHarbour porpoise
There is a directed take of this species in West Greenland amounting to a few hundred a year. Incidental catches of this species are also apparently common along much of the Canadian and US coasts in area 21. Gaskin (1983) summarizes information on the catches of this species, and states that its feeding habits and neritic habitat virtually ensure its vulnerability to a number of net types. Gill nets cause the majority of deaths which may amount to a few thousand a year, although other gear such as cod traps, set nets and weirs are also responsible for some deaths. Food fishes are known to include a number of commercial species including herring, mackerel and small gadoids (Gaskin 1983).
Odobenus rosmarus Walrus
The population in the Atlantic is recovering from severe depletion and at the moment there appears to be no interaction with fisheries, although as Harwood (1981) has pointed out concerning the Pacific population, any development of a shelfish fishery in more northerly waters could alter this situation. Brenton (1979) estimates the population in area 21 to be in the region of 10 000.
Phoca vitulina Harbour seal
A varied diet including commercial species suggests that there is bound to be some interaction between this species and fishermen locally. Bonner (1979c) states that some animals are hunted for fur in northern regions, but there are apparently no data on incidental catches. The population may number around 20 – 30 000 (Bonner 1979c).
Phoca hispida Ringed seal
The northerly distribution of this species may prevent conflicts with fisheries; however flounder, arctic cod and crustaceans are all known to be eaten (Popov 1982). The population in area 21 is unknown, but this is possibly the most numerous seal in Arctic regions, with a total population of 6–7 million (Stirling and Calvert 1979).
Phoca groenlandica Harp seal
This species has been hunted extensively for a considerable length of time, and still supports an annual kill of thousands of pups and adults. Interactions with fisheries have been limited to capelin; the depletion of the capelin stocks of the Newfoundland area have led to the suggestion that this may affect the population dynamics of the capelin eating harp seal (IUCN 1981), but these effects are at present unclear. The NCC (1982) states that “ on the available evidence, it is uncertain whether this stock - for which the range of current estimates is 1–2 million animals - is increasing or decreasing.” They add that changes in the food supply may affect the chances of recovery of this stock.
Erignathus barbatus Bearded seal
There does not appear to be any conflict between this northerly species and fisheries although some commercial species including herring and flounder are known to be eaten (Popov 1982). There are no population estimates from this area (Stirling and Archibald 1979).
Cystophora cristata Hooded seal
Sergeant (1976) states that there is some mortality associated with discarded fragments of netting, and Sergeant (1979) also states that there is some mortality associated with the salmon drift nets of the West Greenland salmon fishery, although he maintains that this is unlikely to have any significant effect on the population. The diet includes a number of commercial species although it is very catholic, which may reduce the likelihood of conflict. The population size is unknown, but may be in the hundreds of thousands (Reeves and Ling 1981). The NCC (1982) adds that although there is no reliable method to estimates the population size, the available evidence suggests that the population is still declining even after a reduction in the size of the commercial harvest.
Halichoerus grypus Grey seal
Food is known to include commercial species including cod, hake, herring, and occasionaly salmon (Mansfield 1963). Although there appears to be no data on incidental kills in area 21, Bonner (1981a) refers to considerable damage to Candian fisheries which is attributed to Grey seals. Nets set for mackerel may be emptied of their catch, and Grey seals may be responsible for stealing cod from line fisheries, and for stealing bait from lobster traps. Grey seals have also been culled in Canada because they are hosts to the nematode Porrocaecum decipiens which infests fish and considerably reduces their value. The population in area 21 may be around 22 000 (Bonner 1979d).
Of the 33 species listed above, at least 12 are known to eat commercial fish species, and 4 or 5 others probably do also. Of the remainder possibly 4 of the baleen whales feed only or mostly on swarming crustacea, and 10 species are thought to feed mostly on squid. The walrus and the striped dolphin may feed on benthic and small mesopelagic organisms respectively, which at present probably present little overlap with fisheries.
At least 7 species have been reported in gear interactions, mostly in fixed and gill nets around Newfoundland. Although the reportage of these gear interactions is relatively good, it would seem probable, given the number of marine mammals which are known to feed on commercial fish stocks in the area, that many more such go unreported. It is also worth noting that even in this area which is one of the better documented fisheries areas, there is very little information relating to presumed or actual ‘biological’ conflict between marine mammals and fisheries. It would seem likely that this is either already, or else is likely to become, an important factor in the population dynamics of a number of species and the future of a number of fisheries, even though it remains poorly documented. This may be particularly important in the case of the harp seal population, which is probably the most important mammalian predator of fish in this area after man.
DEMERSAL FISH RESOURCES
The demersal fish resources of this region have been exploited for centuries, by European as well as North American boats; the cod fishery in particular has been very important in the history of the fisheries of this region (Innis, 1954). As with other temperate water areas the catch is made up to a large extent by comparitively few species, of which the members of the family Gadidae are by far the most important. Cod alone is estimated to have a potential of around 1.5 million tonnes. The FAO Yearbook of Fisheries Statistics recorded the annual catch of all demersal species for 1981 as 1 225 998 tonnes. Nearly all the stocks are heavily fished, and some have been depleted by over-exploitation (see reports from the Northwest Atlantic Fisheries Organisation, NAFO, and its predecessor, the International Commission for the Northwest Atlantic Fisheries, (ICNAF).
GADIDAE
Gadus morhua Atlantic Cod.
The total recorded catch of this species was 588,318 tonnes in 1981. Garrod (1977) lists 10 separate important cod stocks in the northwest Atlantic region. Although cod extends as far north as around 70°N on the coast of West Greenland, the main area of cod exploitation and abundance lies further to the south off Labrador, Newfoundland, and as far south as Nova Scotia, within which area it is the most abundant commercial species.
Cod are known to make annual migratory movements in these regions following the spawning migrations of the capelin stocks, and may be found near the bottom from near shore surf areas to depths exceeding 200m (NOAA 1983). Migrations occur offshore in spring to spawning grounds and fish then move into shallower waters in the summer. Cod is taken both by modern trawlers, now, with the departure of most of the European long range fleets, predominantly Canadian and U.S., and also by artisanal fisheries in cod traps and other types of gear, particularly in the inshore waters of Newfoundland. Of the US catch in 1981 between 11 and 33% of the catch was taken by gill netting (NOAA 1983).
Melanogrammus aeglefinus Haddock.
This species is one of several which are of major commercial importance in the Nova Scotia and New England areas, and which replace the dominance of cod in those more southerly regions. Individuals of this species may weigh up to about 5kg and are most common in depths of 43-135m, ranging from West Greenland to Cape Hatteras (NOAA 1983). Catches for the whole area exceeded 80 000 tonnes in 1981, which represents a recovery from annual catches of less than 30 000 tonnes in the early 1970's, after boom year catches of more than 200 000 tonnes in the late sixties (FAO 1981, Gulland 1983). One of the most important stocks is fished on Georges Bank off New England, which stock alone accounted for 25 000 tonnes of the 1981 catch (NOAA 1983). Almost all of the catch is accounted for by Canada and the US, using gill nets and otter trawls (FAO 1983 NOAA 1983).
Merluccius bilinearis Silver hake.
This species extends from the Newfoundland Banks to South Carolina, with major concentrations again off the New England coast. Spawning occurs in shallow waters from March to November, whilst extensive migrations of adults lead to overwintering in the deeper waters of the Gulf of Maine, and the outer slopes of the continental shelf. Adults may grow up to about 65 cm (NOAA 1983). The catch of this species has declined from over 170 000 tonnes in 1976 to 61 000 tonnes in 1981 (FAO 1983); this is thought to be due to a severe decline in stock biomass which started in the 1960's and which has been recovering only slowly and in places since the early 1970's (NOAA 1983). Of the 61 000 tonnes taken in 1981, 40 000 tonnes were taken by the USSR, and most of the rest by the USA (17 000 tonnes). The fishery is mostly by trawl (Gulland 1971). FAO (1981) estimates the total potential of this species at around 250 – 500 000 tonnes.
Urophycis tenuis White hake.
26 000 tonnes were landed in 1981, of which 19 500 tonnes was taken by Canada, catches having been stable since 1977 at least (FAO 1983).
Pollachius virens Saithe.
58 000 tonnes were taken in 1981 which shows an increase over the preceding 5 year period, two thirds of this was taken by Canada and one third by the U.S. (FAO 1983). The increase in catches is the result of increased directed effort in the past five years where previously saithe was taken mostly as a by-catch with other groundfish species. Saithe are most abundant on the southwestern Scotian Shelf and in the Gulf of Maine. As juveniles they are found in inshore and shallow waters, moving offshore as they grow older. Saithe may grow to about 16kg in weight (NOAA 1983).
SCORPAENIDAE
Sebastes spp. Redfish.
Between 100 and 200 000 tonnes of two or three species of Atlantic redfish have been taken in each of the past 6 years (FAO 1983). The U.S. fishery at least has experienced a decline in CPUE for Sebastesfasciatus and a decline in the index of its abundance (stratified mean catch per tow) in the past 3 or 4 years (NOAA 1983). Gulland (1983) too provides data (table 5–9) indicating a decline in the catches of redfish in ICNAF area 3. Redfish are relatively deepwater species, slow growing, attaining lengths of around 50 cm. They are fished throughout the region, from West and South Greenland (esp.S. marinus south to Newfoundland (S. mentella) and to the Gulf of Maine (esp. S.fasciatus) (FAO 1981, NOAA 1983), almost exclusively by trawl (Gulland 1971).
PLEURONECTIFORMES
Hippoglossoides platessoides American plaice
This species is the most important flatfish species in the region in terms of weight of catch. In 1981 90 000 tonnes were taken (FAO 1983). The main areas of commercial concentrations of this species lie in the southern Gulf of St. Lawrence, and on the shelf off Nova Scotia (FAO 1981). Most of the catch is taken by Canadian ships, but the U.S. takes around 10 000 tonnes from the Gulf of Maine also (FAO 1983, NOAA 1983). This species is found all along the continental shelf from Labrador to Rhode Island, chiefly in waters between 50 and 100 fathoms (90 – 182 m) (NOAA 1983), and adults may attain lengths of up to 80 cm (Pauly 1978).
Reinhardtius hippoglossoides Greenland halibut.
42 000 tonnes of this species were taken in 1981, most of which was taken by Canada (29 000 tonnes), with a small amount taken by Greenland (5 800 tonnes) and the rest taken by foreign ships (FAO 1983). This fish may attain lengths of more than 1 metre, and weights of more than 10 kg (Bowering and Brodie 1981). It is a slow growing species confined to colder waters of the North Pacific and Atlantic Oceans. The fishery in area 21 is pursued in the Davis Strait, and has increased rapidly since 1973 when only 9 000 tonnes were taken (Atkinson et al 1981).
Limanda ferruginea Yellowtail flounder.
Ranging from Labrador to Chesapeake Bay, and occurring in commercial quantities in a number of areas, Georges Bank, off southern New England and Cape Cod, and in Division 3NLO, to the east of Newfoundland. Adults may attain weights of up to lkg, although much of the catch is of smaller individuals, and may be found in water 20 – 30 fathoms (37 – 73m) in depth (NOAA 1983). Total catch was 33 000 tonnes in 1981, of which the USA took 15 000 tonnes and Canada 17 000 (FAO 1983) with a fishing mortality in the US fishery in excess of 1.0 compared with an estimated Fmax of 0.5(NOAA 1983). The fishery is conducted with both trawls and purse seines.
Pseudopleuronectes americanus Winter flounder.
Found from Labrador to Georgia along the North American coast, areas of peak abundance appear to be from Chesapeake Bay to the Gulf of St. Lawrence (NOAA 1983). Catches in 1981 were 23 000 tonnes, nearly all of which (19 000 tonnes) was taken by the U.S.A. (FAO 1983). The status of the stocks are unknown (NOAA 1983).
Glyptocephalus cynoglossus Witch flounder.
13 000 tonnes were taken in 1981, and catches have declined steadily over the preceding 6 years (FAO 1983). This species seems to prefer waters of more than 100m in depth and is most abundant in the areas around the Gulf of Maine. Adults may attain weights of around 2kg (NOAA 1983).
Other demersal species including Cusk (Brosme brosme) weakfish (Cynoscion spp.), roundnose grenadier (Coryphaenoides rupestris) are taken in smaller quantities (less than 10 000 tonnes per year), whilst a number of other species are taken in smaller quantities still.
PELAGIC FISH RESOURCES
In 1981 just over 0.5 million tonnes of pelagic fish resources were landed in the area. Almost all of the major pelagic stocks in this area have been heavily overfished. The bulk of the pelagic catch in this area is made up from just 4 species, but some other species are also important economically, notably the Atlantic salmon.
CLUPEIDAE
Brevoortia tyrannus Menhaden.
The Atlantic menhaden has supported a fishery since the mid nineteenth century; catches peaked in the mid 1950's at around 700 000 tonnes and subsequently declined to under 200 000 tonnes in the late 1960's. Since then catches have been increasing again (Schaaf 1979). The catch in 1981 was recorded as 262 000 for area 21 although the total US catch including that from area 31 exceeded 400 000 tonnes (FAO 1983). The fishery is almost entirely pursued by purse seiners, and the catch is used for fishmeal (Reintjes et al 1978).
Clupea harengus Atlantic herring.
The total catch in 1981 was 224 000 tonnes, a considerable decline from catches in excess of 1 million tonnes in the late 1960's, stocks having been greatly overfished. Herring are found along the continental shelf from Labrador to Cape Hatteras, and are fished in at least 5 separate stocks from Newfoundland to the Gulf of Maine which is the area of their greatest abundance (NOAA 1983, Sissenwine and Waring 1979). The catch is taken almost entirely by Canada and the US and employs both fixed and mobile gear (NOAA 1983).
Mallotus villosus Capelin.
The offshore capelin fishery began in the early 1970's as an industrial fishery of a few thousand tonnes and was quickly expanded over the next few years. In 1976 more than 360 000 tonnes were taken and the offshore stocks were quickly depleted so that no offshore fishing was allowed in 1979 or 1980 (FAO 1983, Carscadden et al 1981). In the meanwhile the inshore fishery has expanded, so that the total catch in 1981 was recorded as 39 000 tonnes (FAO 1983). Some anxiety has been expressed over the state of the capelin stocks in relation to the feeding habits of harp seals, which are known to feed extensively on the capelin, and there is some evidence that the depletion of capelin may have affected the energetics of the harp seals (IUCN 1981).
SCOMBRIDAE
Scomber scombrus Atlantic mackerel.
The catch of this species in area 21 in 1976 was 242 000 tonnes, the next year this had dropped to 75 000 tonnes and currently (1981) the catch statistics show a catch of 28 000 tonnes (FAO 1983). Catches in the early 1970's were even higher, 420 000 tonnes in 1973, due to the intensive international fishery of that time and exceptional recruitment in the late 1960's. Most of the catch then was taken in ICNAF subarea 5 (off Cape Cod). By 1977 the number of countries participating in this fishery had been greatly reduced. The offshore fishery employs both purse seines and gill nets, whereas inshore small boat fisheries employ a great range of gear types, both fixed and mobile (Anderson and Paciorkowski 1980), some of which (set nets) are known to capture marine mammals incidentally (Gaskin 1983). The catch of mackerel is mostly divided amongst Canadian, US and Polish boats now, with the US taking less than 5000 tonnes (NOAA 1983).
SALMONIDAE
Salmo salar Atlantic salmon.
The Atlantic salmon is fished in the rivers and estuaries of a number of countries on both sides of the Atlantic. There are also important pelagic fisheries in feeding areas at sea, notably at West Greenland. Although catches in this region are usually only around 1 000 tonnes, and the total fishery for this species in the North West Atlantic is around 3 000 tonnes per annum, this represents an important fishery economically. Salmon at sea are taken largely by drift netting, and are taken along the coast upon their returns to their native rivers to breed by a number of gear types, especially fixed nets. Drift nets are known to cause some mortality to small cetaceans, and pinnipeds are also seen by salmon fishermen as pests, either as vectors of parasites or as predators on salmon (Christensen and Lear 1974, IUCN 1981).
INVERTEBRATE RESOURCES
A number of species figure prominently in the catch statistics of this region. Gulland (1983) points out that scallops and clams are over-estimated because their weights include the shell, and that by far the most valuable species in more northerly waters is the deep water shrimp Pandalus borealis, which is trawled for in the Davis Strait; 45 000 tonnes were taken in 1981. The blue crab Callinectes sapidus is also an important commercial species locally in the Chesapeake Bay area, where over 50 000 tonnes were taken in 1981, mostly by traps set on long lines.
SQUIDS
Nearly 50 000 tonnes of squid were taken from area 21 in 1981 (FAO 1983). The two main commercial species are Loligo pealei and Illex illecebrosus, which are caught both by distant water foreign fleets at the edge of the continental shelf, and by local boats in inshore waters (NOAA 1983). Locally jigging appears to be the main method of catching squid (Voss 1973). Voss (1973) has noted the large numbers of squid eating marine mammals in this region and has agreed with Gulland (1971) that the resource may be very large.
Canada and the United States dominate the fisheries of this area, with catches of 1.16 and 1.24 million tonnes respectively for 1981. Greenland takes around 100 000 tonnes per annum, and a number of European countries also take some fish and squid in this area. Gulland (1983) has pointed out the importance of cod both historically and at present in the fisheries of this area, and indeed the Gadid family accounts for around 800 000 of the 2 800 000 tonnes of all species landed in 1981. Demersal fish accounted for 1 225 000 tonnes and pelagics around 500 000, the remainder being invertebrate.
A large portion of the total catch is therefore seen to be taken by trawling, the development of which is summarised by Gulland (1983). Purse seining is also important in pelagic fishing (see Pelagic Resources). These two methods of fishing appear to involve little interaction with marine mammals in this area.
Traditional fishing gear such as set nets, traps and weirs, and hand lines are still important in many of the coastal regions (Gulland 1983), and most of the species of fish mentioned above are also caught in inshore waters in such gear. These types of gear feature very prominently in the interactions with marine mammals as they seem particularly prone to incidental capture of, and often destruction by, marine mammals especially whales. Lien (1981) states that collisions between fishing gear and whales have increased over the past 10 years for a number of reasons, biological and economic, and that damages to gear and lost fish in 1979 and 1980 were equivalent to 2–3% of the total annual value of the inshore Newfoundland catch.
Gaskin (1983) amongst others has also stressed the importance of the introduction of monofilament gill nets in marine mammal entrapments. The number of fishermen fishing with such gear in Canada as suggested by survey work, far exceeded the number to whom licences have been supplied. This type of gear is, in Gaskin's opinion responsible for far more deaths to small cetaceans than other forms of gear.
To summarise, it would appear that whereas commercial trawling and purse seining equipment poses little threat of operational interaction with marine mammals or vice versa, coastal gear such as the traditional set net gears may be more prone to such conflicts. Similarly gill nets made from monofilament fibre feature prominently in gear conflicts with marine mammals. Large marine mammals such as baleen whales and in particular the humpback whales Megaptera novaeangliae, are most often implicated in coastal gear. Lien (1981) has estimated that humpbacks are responsible for 70–90% of such damage. Other species involved are Balaenoptera acutorostrata, Balaenoptera physalus, Eubalaena glacialis, Delphinapterus leucas, and Globicephala melaena. Not all such conflicts involve nets, and a number of entanglements have been reported between whales and crab pot lines and other forms of guy-line.
Amongst the smaller marine mammals gill netting is thought to cause most mortality; the species involved here include Phocaena phocaena, Lagenorhynchus acutus and Cystophora cristata, although humpbacks and other larger cetaceans are also very often caught in such gear.
Until recently biological interactions between marine mammals and fisheries in this area were not at all obvious. The recent expansion of many fisheries, both of traditional ones and the opening up of fisheries for relatively new species like capelin, has meant that such interactions have become more visible. At the same time many marine mammal species which were until recently at very low levels of abundance have started to increase once more. The reduction of capelin stocks, coupled with the recovery of the humpback whale
population in area 21, has lead to the suggestion that the shortage of capelin may now be hindering further recovery of the humpback population (Whitehead 1982). At the same time the relative changes in the two populations may be a factor in the increase in gear damage in Newfoundland. The capelin shortage could also be affecting the harp seal population (IUCN 1981).
The expansion of fisheries into more northerly waters, such as the recent increase in catches of Greenland halibut and the shrimp Pandalus borealis could also create a new level of interaction with a number of marine mammal species which inhabit those waters and feed on such prey items, for example some of the seals and the narwhal and white whale.
The rapid expansion of the squid fishery should not go unmentioned either. The abundance of squid eating marine mammals in the area has been noted as an indicator of the abundance of squid. A number of these species, such as pothead or pilot whales and sperm whales may now be increasing in population size, so that conflict cannot be ruled out if the squid fishery continues to expand. Mercer (1975) has already pointed out that when peaks in pilot whale landings started to decline, peaks in squid catches increased. The reverse might therefore be expected as pilot whale abundance increases.
The more obvious interactions in this area are principally operational in nature, despite the fact that this area is one of the most heavily fished in the world. This is partly due to the fact that the species which are caught do not overlap to such a great extent with the main food items of marine mammals in the area.
Operational interactions
Gear interactions are largely coastal ones involving small scale fisheries. Right whales, fin whales, minke whales, humpback whales, white-sided dolphins, harbour porpoises and hooded seals are all known to become entangled in a variety of gears, notably inshore set nets and traps.
Biological interactions
Grey seals are vectors of fish parasites which can cause considerable loss to the cod fishery in particular. Recently there has been the suggestion that biological interactions between marine mammals and fisheries may be becoming more important. Expansion of certain fisheries may impede the recovery of a number of marine mammal stocks. Harp seals and pilot whales in particular may be important potential competitors with fisheries.
Eubalaena glacialis Right whale
The number of this species which remain in the North Atlantic is very small, perhaps only a few hundred. No interactions with fisheries are known or likely at present and no commercial fish species are eaten.
Balaena mysticetus Bowhead whale
Jonsgaard (1981) states that at most 9 animals have been sighted in this area in the last 23 years; the possibility of a breeding stock is therefore slight, and interactions with fisheries are also unlikely.
Balaenoptera physalus Fin whale
The population size in the north east Atlantic is unknown, but may be in the thousands. This species like other baleen whales is depleted, but unlike some others is known to feed on commercial fish species (Tomilin 1967), such as herring and capelin, stocks of both of which are at present heavily exploited in the area. The possibility that the fishery may therefore affect the recovery of fin whale stocks cannot be excluded.
Balaenoptera musculus Blue whale
Presently also at very low levels of abundance; 245 sightings of 462 blue whales were reported by Icelandic whaling vessels in the summer 1982 whaling season (IWC SC/35/Prog. Rep. Iceland 1983). This species does not feed on fish, and is unlikely to be affected by commercial fisheries.
Balaenoptera acutorostrata Minke whale
The minke whale has been well known as a fish eater, especially of herring, for several centuries at least (Von Brandt 1972). Jonsgaard (1982) amongst others has also noted a number of commercial species eaten by the minke whale, including cod. The minke whale may be less abundant now than in former years, as are a number of its food species, in area 27, which may be bringing it into closer conflict with several fisheries, notably those for capelin, herring and cod. As yet however, little has been reported on the matter.
Balaenoptera borealis Sei whale
The sei whale population size in area 27 is unknown, but depleted, presumably numbering no more than a few thousand. Fish are not an important part of the diet, however, so it may be that this species does not interact with any fishery.
Megaptera novaeangliae Humpback whale
The report of the Sub-committee on Protected Species and Aboriginal Whaling (IWC 1982) suggests that this stock spends the winter in the Caribbean region, whilst stating that some animals have been seen in the Azores in the past. No population estimate is available; however, this is unlikely to be more than a few thousand. The diet of this whale is known to include fish species, such as capelin, (Tomilin 1967) for which there is an intensive fishery in the north eastern parts of area 27. The possibility of this fishery affecting the rate of recovery of the population of humpbacks in area 27 cannot therefore be overlooked.
Mesoplodon bidens Sowerby's beaked whale.
Very rarely seen, there is little likelihood of this deepwater squid eating species interacting with any commercial fisheries at present.
Mesoplodon europaeus Gervais' beaked whale.
Occasionally straggling into European waters on the Gulf Stream, this is another deep-water species, unlikely to come into contact with any fisheries.
Mesoplodon grayi Gray's beaked whale.
This species too is rarely seen and deepwater in habitat.
Mesoplodon mirus True's beaked whale.
As with the other Mesoplodon species this one is rare and unlikely to conflict with fisheries.
Ziphius cavirostris Cuvier's beaked whale.
Rarely seen, this species feeds on squid and is unlikely to be involved in any interaction with fisheries at present.
Hyperoodon ampullatus Northern bottlenose whale
Mitchell (1977) has provided evidence that the population is at present depleted after decades of hunting in the North Atlantic. The bottlenose whale prefers deeper water, feeds on squid and is unlikely to interact with fisheries, unless squid stocks are to become heavily exploited.
Physter macrocephalus Sperm whale
Townsend's maps show the main areas of sperm whale distribution around the Azores, where there was and still is a whaling industry based on this species (see e.g. Clarke 1981). The population in the North East Atlantic is unknown but may be presumed to be in the thousands. The report of the Sub-committee on Sperm Whales (IWC 1982) gives an estimate of 58 000 for the stock exploited by Icelandic whales. As with other mainly squid eating species, no interaction with fisheries is likely unless an intensive squid fishery is developed.
Kogia breviceps Pygmy sperm whale
Duguy (1977) refers to this species as unusual in French waters, and although Clarke (1981) records it as present in the Azores it is not common there either. Nothing is known of the size of the population, and as the diet is also not clear, there is nothing that can be surmised about interactions with fisheries.
Monodon monoceros Narwhal
Known to eat commercial fish species (Tomilin 1967), the population size in area 27 is unknown, but may still be severely reduced (Tomilin 1967). This again brings up the possibility of some interaction with commercial fisheries for food species, although Tomilin suggests the main diet in those areas is pelagic squid.
Delphinapterus leucas White whale
Bjorge et al (1981) have noted the fish eating habits of this species which apparently has also annoyed local fishermen on at least one occasion in Finnmark, Norway, after an ‘aberrant migration’ into that area. Tomilin (1967) describes it as widespread in cold coastal waters, and the Report of the Sub-Committee on Small Cetaceans (IWC 1982) gives figures of 232 and 1 570 as minimum and maximum counts of white whales in the Barents, Kara and White Seas. Tomilin also records a number of commercial fish species in the diet, including salmon, so there is at least the potential for conflict.
Steno bredanensis Rough-toothed dolphin
Duguy (1977) does not record this species in French waters, and Clarke (1981) does not record it in the Azores either. Hershkovitz (1966), however, records the distribution of this species as from the Netherlands to Portugal. It is presumably rare in this area, and as its diet here is also unknown, the likelihood of interaction with fisheries cannot be assessed.
Pseudorca crassidens False killer whale
Apparently not a common species in this area, and one without recorded interactions with fisheries here either. Given its pelagic and oceanic habits the chances of interaction seem small, although in other areas commercial fish are eaten.
Orcinus orca Killer whale
There have been a number of suggestions that killer whales may be deleterious to fish stocks, particularly the herring stocks around Norway (see Hiby and Harwood 1981), but theoretical analysis by Hiby and Harwood has shown that killer whales do not necessarily affect the dynamics of herring. There is no doubt, however that this species is seen as a nuisance by some fishermen at least. Christensen (1982) also records the fact that fishermen off Iceland have found killer whales to be such a nuisance in fishing for halibut that at times they have had to abandon the fishing. Mitchell (1975a) writes that killer whales in Icelandic coastal waters were perceived as such a threat that the U.S. Navy was asked to get rid of them. Hundreds were killed this way in the 1950's. There are no population estimates for area 27, but this species is certainly not rare, at least in colder coastal waters.
Globicephala melaena Long-finned pilot whale.
This species occasionally turns up in fishing nets as an incidental catch in area 27. Duguy and Hussenot (1982) give details of 5 such incidental captures on the French Atlantic coast between 1971 and 1981, 3 in bottom or midwater trawls, and 2 in gill nets. There has also been a certain amount of exploitation of this species, notably in the Faroe Islands, where over 1 000 are taken a year. The population size is unknown but presumed stable, and may number in the hundreds of thousands. The food is chiefly squid (Sergeant 1962) although fish may also be eaten.
Globicephala macrorhynchus Short-finned pilot whale.
Clarke (1981) records this species from the Azores, although it is not apparently common, and does not occur much further north than this. Interactions with fisheries are therefore unlikely.
Lagenorhynchus albirostris White-beaked dolphin.
This species is known to feed on commercial fish, including cod, whiting and herring (Tomilin 1967). According to Tomilin it is most common in the North Sea especially up to Norway and the eastern coast of Britain. Aguayo (1978) considered it to be one of the ‘normal inhabitants’ of the Baltic. Leatherwood and Reeves (1983) state that a few are taken accidentally each year in trawl nets in the North Sea. The occurrence of a number of commercial fish species in the diet may indicate some degree of competition for food resources.
Lagenorhynchus acutus Atlantic white-sided dolphin
Also known to eat commercial fish species, the population size of this species is unknown, but Tomilin (1967) states that it enters Norwegian fjiords in vast numbers in pursuit of herring. It has also been recorded in the Baltic, but Aguayo (1978) suggests that it may be rare there.
Tursiops truncatus Bottlenose dolphin
Incidental catches of this species are reported by Duguy (1977) and Duguy and Hussenot (1982) who state that 3 have been taken in mid or deep water trawls on the French Atlantic coast in the 10 years 1971–-1981. Duguy (1977) says this species is widespread but not common, and Aguayo (1978) suggests that it may be a regular visitor to the Baltic. The population size is unknown, and the diet in this area has received little attention, but presumably includes some commercial species. Interactions with fisheries are probably more widespread than reported for this species.
Grampus griseus Risso's dolphin
This species is also incidentally caught in nets on occasion. Duguy and Hussenot (1982) report 2 found in gill nets from 1971 to 1981 along the French Atlantic coast. Clarke (1981) suggests that this species is common in the Azores, whereas Aguayo (1978) states that it only visits the Baltic on rare occasions. The diet is chiefly squid, and so apart from the occasional net entanglement, there seems little likelihood of any interaction with fisheries at present.
Stenella coeruleoalba Striped dolphin
This species is yet another which is infrequently found in nets as an incidental capture. Duguy and Hussenot (1982) report 2 in gill nets on the Atlantic French coast, but also state that several thousand of this species and the common dolphin may have been killed in the ten year period 1971–1981, by French fishermen at sea, for food. The effect of this on the population is unknown. Diet in this area is unclear, as are any other potential interactions with fisheries.
Delphinus delphis Common dolphin
Duguy and Hussenot (1982) report 25 individuals of this species being captured between 1971 and 1981; 2 on shark longlines, 8 in gill nets and 15 in trawls. Collet (1983) also records 16 confirmed incidental captures in French Atlantic coastal fisheries in 1981. This species is known to eat sprats, sardines and anchovies off the coast of France (Tomilin 1967). It is probably also caught regularly elsewhere, but does not seem to be reported as such. Duguy (1977) states that it is the most common small cetacean on the Atlantic French coast, and adds that large numbers of this species are taken by French fishermen whilst at sea as fresh meat for the boat crews. The effect of this on the population is unknown, as is the extent of the interaction between this species and fisheries which operate on its food species.
Phocoena phocoena Harbour porpoise
Andersen and Clausen (1983) have suggested that a considerable number of this species, possibly hundreds per year may be taken in Danish trawl nets. Gaskin (1983) gives data on the numbers of this species stranded in Scottish nets. Up to 24 have been taken in a year, mostly in set nets which fish for cod. Gaskin also cites numerous other authors' opinions that this species may be becoming rarer in area 27, although Easton et al (1982) suggest otherwise on the basis of British stranding records. Aguayo (1978) suggests that this species is one of the ‘normal inhabitants’ of the Baltic, but gives some indication that it may now be much rarer there than in previous years. The population size is unknown, and the extent of interaction with fisheries is also unclear, but there is certainly some by-catch, and presumably some overlap in the fish species taken. Tomilin (1967) includes herring, capelin, mackerel, sardine, cod, Baltic cod, whiting, eel, small salmonids, and sole in the diet of this species for the Atlantic.
Odobenus rosmarus Walrus
The population in area 27 is confined to two regions, around Spitsbergen and Novaya Zemlya, and probably numbers no more than a few hundred (Fay 1981). There is no apparent conflict with fisheries at present, and none likely unless a mollusc fishery is developed in these waters.
Phoca vitulina Harbour seal
Known to eat commercial species of fish, especially in shallow or inshore waters, the population in the north east Atlantic may total about 50 000. Between 6 and 8 000 individuals are apparently killed by hunting every year in area 27 (Bonner 1979c), mostly in Iceland. The population in the Baltic is currently at a critically low level, with perhaps only 150 animals left (Almkvist 1977); there are also said to be complaints from fishermen in the Baltic with regard to this seal (Almkvist 1977). There does not appear to be any data on incidental catches, but it is clear that as a result of the diet of this species there is competition with fisheries in a number of places (Bigg 1981).
Phoca hispida Ringed seal
One of the two main pinniped inhabitants of the Baltic, this species is otherwise confined to the more northerly regions of area 27, in the Barents Sea (Frost and Lowry 1981). It is also said to be the most abundant seal in the Arctic with a total population of 6-7 million; there is a harvest in the White Sea of 3 500 annually (Stirling and Calvert 1979). Stenman (1978) suggests that the ringed seal is responsible for damage to salmon fisheries in the Baltic, but this is the only area where such interactions are recorded, although the diet may include some commercial species (Frost and Lowry 1981).
Phoca groenlandica Harp seal.
Although most numerous in area 21, there are sizeable populations in area 27 also. The population in the Barents Sea has come into serious conflict with fishermen in northern Norway recently. In the years from 1978 to 1981 large numbers of these seals migrated south to feed on capelin which migrates to the coast of Norway. Bjorge et al (1981) state that as many as 10 000 harp seals may subsequently have drowned in cod set nets for each of these years, causing millions of kroner damage to nets and catch. Oritsland (pers. comm.) reports that invasions of the coast of Finnmark by large numbers of harp seals have continued in 1982, 1983 and 1984.
Erignathus barbatus Bearded seal.
Burns (1981) cites Chapskii's (1966) estimate of 300 000 for the entire North Atlantic, this species is confined to more northerly regions and feeds on benthic organisms. At present there are no apparent interactions with fisheries, and none would seem likely.
Cystophora cristata Hooded seal
Distributed around Jan Meyen Island and as far east as Bear Island, the population size in this area is unknown, but may be in the hundreds of thousands (Reeves and Ling 1981). Sergeant (1976 cited in Reeves and Ling) has suggested redfish may be an important part of the diet, in which case some competition with fisheries may occur. Oritsland (pers. comm.) reports that some hooded seals are taken on longlines and in driftnets set for salmon off the coast of northern Norway, although damage to fish and gear is apparently of minor importance.
Halichoerus grypus Grey seal
The population of this species is estimated at around 100 000 individuals in area 27, very few of which remain in the Baltic. The species is commonly found feeding inshore and is continuously in conflict with fishermen due to the damage it causes to nets, especially set nets, and catch, especially salmon. Stenman (1978) gives details for the Baltic, where around 2% of the salmon catch is said to be damaged by grey seals. Grey seals are also a nuisance in Scotland and Norway (ICES 1981), and it has been suggested may cause serious loss to the fishing industries of such countries as quite a number of commercial species are known to be included in the diet. (Parrish and Shearer 1978, ICES 1981). Recent work by the Sea Mammal Research Unit in the UK has suggested that this effect may have been overestimated as much of the grey seal diet may consist of small less valuable fish such as sand eels (NCC 1984). The Sea Mammal Research Unit have examined seal faeces from 9 haulout sites around the British Isles. Their results indicate that, overall, 60% of the diet of British grey seals is made up of sand eels (Ammodytes), 12.4% was tusk and ling (Brosme brosme and Molva molva), 6.7% Trisopterus, 6.3% whiting (Merlangius merlangius), 5.8% flatfish, 5.1% haddock saithe and pollack, 3% cod, and less than 1% blue whiting, blenny, goby, herring, sprat and horsemackerel.
There is also the problem that grey seals are known to be hosts for the fish parasite Phoconoema decipiens (IUCN 1981) which also causes losses to the fishing industry. This may be a particular problem locally, and has even been the reason for some culling of grey seals (Bonner 1981a).
Monachus monachus Mediterranean monk seal
Sergeant et al (1978) record a few isolated sightings of this species at the Azores, but there is probably no breeding population there and the numbers of animals involved probably precludes any appreciable interaction with fisheries in this area.
Interactions between marine mammals and fisheries are comparatively well documented in area 27, and yet it is apparent that for a number of species, such as the harbour porpoise, common dolphin and harbour seal, the extent of interaction remains unclear. Of the 36 species described above, at least 17 are known to eat commercial fish species. A further 8 or 9 are thought to feed primarily on squid. The extent of fishing operations in area 27 is such that almost any marine mammal which is known to eat commercial fish species will compete to some degree with a fishery. Similarly there are probably few species, perhaps only the very rarely recorded ones, which are not likely to become incidentally captured in fishing operations in some part of the area.
Fortunately, incidental captures in this area do not seem to involve very large numbers of animals, the exception perhaps being provided by Andersen and Clausen's (1983) account of the harbour porpoise in Danish trawl nets, and the unusual catches of harp seals in recent years in northern Norway.
As might be expected in an area which is both heavily fished and has a large number of feeding marine mammal species there are a comparatively large number of recorded ‘competitive’ conflicts between marine mammals and fisheries.
DEMERSAL FISH RESOURCES
Catches of demersal species in 1981 totalled 5 469 846 tonnes (FAO 1983). As with the northwest Atlantic, the main commercial species are flatfish, especially the plaice, and the gadid family especially cod. The commercial fisheries of this region are amongst the oldest in the world and many of the modern fishing methods were first developed in this region; perhaps as a result of this many of the stocks in this region are fully or over-exploited. The region remains however the second most productive in the world after area 61.
GADIDAE
Gadus morhua Atlantic cod
This species is perhaps the most important of all in this region and has been fished for from European shores for many hundreds of years. There are numerous stocks, scattered from the English channel through the North Sea to the Baltic in the east to Iceland in the west and to the Barents Sea in the north. Many of these stocks are probably over exploited as the reports of the ICES working groups on roundfish demonstrate. In the North Sea for example the stock has been declining whilst catches have remained stable; the fishing mortality has increased to around 1.0, whereas Fmax may be around 0.25. Similarly in division 6a, to the west of Scotland the current fishing mortality far exceeds the value of Fmax.
In most areas cod is trawled for, although in the North Sea the Danish seine is also used for this and other species of demersal fish (Gulland 1983) as an effective alternative to trawling. In a number of areas more traditional methods employing stake nets, lines, gill nets, etc. are still used. Bjorge et al (1981) refer to set nets in northern Norway for the entrapment of cod, and Gaskin (1983) also refers to stake nets for cod, trapping harbour porpoises in Scotland. The total catch of cod in area 27 exceeded 1.7 million tonnes in 1981.
Micromesistius poutassou Blue whiting
This species produces the next largest catch after cod of the demersal species in area 27. 870 000 tonnes were taken in 1981 whereas over one million were taken in each of the two preceding years. The main spawning area is to the west and north of Scotland, ranging from off the coast of southwest Ireland up to the area between the Farce Islands and the Orkneys. Ranging as an adult from the Mediterranean to Spitzbergen, the species was until recently only very lightly exploited. It is found during the spawning season at several hundred metres depth over the edge of the continental shelf, and as it is too dispersed for much of the rest of the year this is where most of the fishing effort is concentrated. The fishery is pursued mostly by large trawlers (over 40m in length) with the use of single mid water trawls, and occasionally high headline bottom trawls where the fish are close to the shelf edge (Pawson 1979).
Pollachius virens Saithe
Mainly distributed to the west of the British Isles, in the northern North Sea, and around the Faroes, Iceland and Norway. In 1981 this species yielded over 420 000 tonnes, from at least 5 stocks identified by the ICES Saithe working group. The fishery is mostly pursued by trawlers, although there is a significant purse seine fishery for the juveniles in the North Sea and off Norway, carried out mostly by Norwegian ships.
Trisopterus esmarkii Norway pout.
This is one of the so called industrial fish, used solely for reduction to meal and oil which has only recently been exploited. It is a small fish, usually found within a few metres of the sea bed in water 100 to 250 metres deep. The fish is confined to the northern North Sea and the adjacent areas, and appears to be caught mostly by Danish trawlers. The catch has declined from a peak of over 800 000 tonnes in 1974, but the status of the stock is far from clear as recruitment appears to be highly variable.
Melanogrammus aeglefinus Haddock
This species has a similar though less extensive distribution to cod. It has apparently been over exploited in the North Sea and to the west of Scotland, but catches around the Faroes have remained more stable. Total catches of this species were 333 000 tonnes in 1981, up on 1980, but below the level of the early 1970's when more than 500 000 tonnes were being caught annually. The fishery is mainly pursued by trawling, although Gulland (1983) points out the North Sea Danish seine fishery for this and other species.
Merlangius merlangius Whiting
Total catches of this species in 1981 were 189 000 tonnes, and have been fairly stable for the last 5 years, but are lower than catches in the mid seventies which exceeded 250 000 tonnes (FAO 1983, 1977). This species is largely confined to the waters around the British Isles, with small spawning grounds and populations centred on the Faroe Islands and southwest Iceland. The population appears to be fully exploited at present.
SCORPAENIDAE
Sebastes spp. Redfish
Deepwater slow growing fish, these species are mainly found in northerly waters from south of Greenland to the Barents Sea. The annual catch in 1981 was 250 000 tonnes.
AMMODYTIDAE
Ammodytes spp. Sandeels
The main species in this fishery is A. marinus, which is distributed in commercial quantities around the British Isles, in the North Sea and along the coast of Norway. Adults are most abundant at depths of between 20 and 40 metres in the northern North Sea, although in recent years deeper waters have also been exploited successfully. Catches increased to a peak in 1978 of 800 000 tonnes, and have since decreased to 630 000 tonnes in 1981. 66% of landings in 1978 came from the Dogger Bank in the northern North Sea. There is still considerable uncertainty as to the status of this stock. Most of the catch is taken by Danish trawlers.
PLEURONECTIDAE
Pleuronectes platessa Plaice
This species has been exploited for a long time and was one of the first to be fished for with trawls in the North Sea. Catches have been relatively stable, around 150 000 for a number of years, but most stocks have been heavily exploited. The fishing mortality on the North Sea stock is thought to be well in excess of Fmax. This species is mostly fished for by trawl and by Danish seines.
OTHER SPECIES
The species mentioned above all yielded more than 100 000 tonnes in 1981. A number of other stocks however yield catches in excess of 10 000 tonnes, which in an area less productive than this would constitute a major commercial yield. Amongst the gadoids, hake and ling (Merluccius merluccius and Molva molva) yielded 77 and 58 thousand tonnes respectively in 1981. The sole Solea solea yielded 25 000 tonnes which is an important catch economically, and the monkfish or anglerfish (Lophius piscatorius) also yielded a sizeable catch in 1981 of 49 000 tonnes.
PELAGIC FISH RESOURCES
Some 5 million tonnes of pelagic fish were taken in 1981. Of this total over half consists of capelin, largely used for reduction to meal and oil, which has replaced herring as the most important species by weight. Many herring stocks have collapsed through overfishing, and are now at a low level. Most other pelagic species are probably fully exploited.
OSMERIDAE
Mallotus villosus Capelin
The capelin stocks of Iceland, northern Norway and the Barents Sea have only been exploited since the 1960's, since when catches have risen to a peak of 3.7 million tonnes in 1977, and have since dropped off slightly. The fishery is largely pursued by Icelandic, Soviet and Norwegian boats using purse seines. Gulland (1983) states that the stocks appear to be in a reasonably healthy state.
CLUPEIDAE
Clupea harengus Atlantic herring
Once one of the two most important fish species in the northeast Atlantic, the herring has been overfished to such an extent that recruitment in a number of places has all but disappeared. Herring has been and still is fished for in a number of ways, but perhaps most effectively by the purse seine. Catch quotas on most stocks have been greatly reduced, in some cases to zero, and there are signs of recovery in some areas.
Sprattus sprattus Sprat One of a number of ‘industrial’ fish taken in large quantities (238 000 tonnes in 1981) chiefly by Danish boats using trawls, in coastal waters around the North Sea and in the Baltic. There has been some debate as to the effect this fishery may be having on the recovery of the North Sea stocks of the herring, as considerable quantities of herring are also taken as by-catch by this fishery.
Sardina pilchardus Sardine
A more southerly species, taken in the coastal waters off France Spain and Portugal, with a catch in 1981 of over 500 000 tonnes. Most of this catch was taken by Portuguese and Spanish boats, the majority of which are small inshore vessels under 50 GRT (Agra Europe 1981).
CARANGIDAE
Trachurus trachurus Horse mackerel
156 000 tonnes were taken in the southern region of area 21 in 1981, which is a decrease from the early 1970's, when over 300 000 tonnes were taken.
SCOMBRIDAE
Scomber scombrus Mackerel
About 575 000 tonnes were taken in 1981, from 2 stocks, one in the North Sea and one to the west of Britain. ICES working group reports reveal that both of these stocks are over exploited, and it seems doubtful that the North Sea can continue to support the size of fishery that it currently does. Mackerel are taken in a variety of ways, most effectively perhaps by purse seining, but in some areas such as south west England, handlining is also used.
Other important pelagic fish stocks include the anchovy (29 000 tonnes) in the southern region, and a number of tuna species which although they do not support a great weight of catch are nevertheless important commercially. Albacore Thunnus alalunga is the most productive tuna species, with 28 000 tonnes taken in 1981. Salmon too should be mentioned particularly as it is still taken in traditional set net along coasts of Scotland and Scandinavia, where there is sometimes considerable antagonism between salmon fishermen and grey seals which frequently visit salmon nets, damaging gear and catch.
INVERTEBRATE RESOURCES
CRUSTACEA
A number of species are commercially important notably Cancer pagurus, the edible crab, Pandalus borealis, the northern prawn, Nephrops norvegicus the Norway lobster, and Crangon crangon the common shrimp. These species are taken in a number of ways. The northern prawn is trawled for by Danish boats in the Kattegat and Skagerak, and by other trawlers further north also (54 000 tonnes in 1981). The common shrimp (40 000 tonnes) is taken particularly in sandy estuaries around the North Sea often with special shrimp nets. (Holthuis 1980).
MOLLUSCA
Cockles (Cardium edule), mussels (Mytilus edulis), scallops (Pecten maximus),and oysters (Crassostrea spp.) are all important locally, and are mostly harvested in a small scale manner, often by hand.
CEPHALOPODA
Squid forms a remarkably small part of the total catch in this area, around 35 000 tonnes in 1981 or 0.2% of the total yield of all species. A further 15 000 tonnes of octopus were taken. Voss (1973) states that most of the squid catch is incidental to trawl fisheries for finfish, and that the total potential for the northeast Atlantic is much greater than current catches.
This area is one of the most productive in the world with a total production of over 11.6 million tonnes in 1981, it ranks second after the Northwest Pacific. Gulland (1983) divides the area into 4 major subregions, which are the northern region from Greenland to Iceland and north Norway and Russia, the Baltic Sea, the area around the British Isles including the North Sea, and the southern region from Ushant to Gibralter.
Gulland suggests that the proximity of markets coupled with the high productivity of the area has been responsible for the early and sustained development of fisheries here. Each of Gulland's subregions has a group of fish which are locally important. So in the north, cod and, until recently, herring were the most important. Now redfish, haddock, and most notably capelin have also become important. Further south a larger number of species, cod, herring, mackerel, sole, plaice, whiting and haddock have all been important, and still are, but Norway pout, sand eel, sprat and blue whiting are added to the list in recent years. In the Baltic, again cod and herring are important, the latter species having played an important role in the economy of the Baltic historically (Cushing 1982). Sprat is the other important fish in the Baltic, though in recent years catches there have declined as the numbers of sprats has declined dramatically. In the southern region, sardines, hake and sea breams replace the northern species in importance.
The productivity of the region, together with its complex political and geographical structure makes any simple unravelling of the fisheries very difficult. Norway has the largest catch in this area of more than 2.5 million tonnes in 1981 most of which was capelin (1.3 million tonnes). The Soviet Union, Iceland and Denmark all also took more than 1 million tonnes in 1981. After this the UK, France, the Federal Republic of Germany, the Netherlands and Spain are all important in terms of total catch.
The fishing methods of area 27 are dominated by the trawl and purse seine both of which were developed in this area, but Gulland (1983) points out that these two methods have not totally eclipsed the older fishing techniques. Danish seines are still used in the North Sea, and set nets are also still used in a number of places. Gill nets are still used in Norway and Iceland to catch spawning cod. Traps and shrimp nets are also used in the capture of crustacean species. The region therefore contains a rich mixture of ancient and modern methods of fishing, maintained by a number of economic, social and geographical factors.
There are numerous reports of incidental captures in this area involving small cetaceans in particular. Many of these are reported to the Small Cetacean Sub-Committee of the IWC.
Operational interactions
Common dolphins and harbour porpoises are commonly caught in European waters in a variety of gears including trawls.
Harp seals have been taken incidentally in cod nets in large numbers in northern Norway.
Striped, Risso's and bottlenose dolphins as well as pilot whales and some seal species are all occasionally caught in trawl and gill nets.
It is noticeable that in contrast to area 21 few if any large cetaceans are recorded as having been captured incidentally. This may be because of different fishing methods, or else the baleen whales in this area feed in areas where set nets and other forms of gear in which they may be prone to become trapped, may not be used.
Biological interactions
Competitive interactions in this area as elsewhere are difficult to ascertain. Nevertheless it would seem that a number of species of marine mammal could well be in direct competition with commercial fisheries at present. These include the fin and humpback whales currently recovering from over exploitation and feeding on heavily exploited fish stocks. Other species may not be depleted to the same degree, but may still be affected by commercial fisheries. On the other hand in two cases where fisheries were thought to be suffering from competition with marine mammals, it has been suggested that the effects may not be as serious as had been claimed. The killer whales in Norway were claimed to be affecting herring stock recovery, but Hiby and Harwood (1981) in a theoretical analysis have shown that this need not be necessarily so. Similarly, the effects of grey seals on salmon fisheries have also been shown to be less dramatic than had been claimed (Stenman 1978, NERC 1984), although locally they are still often regared as a serious pest.
Eubalaena glacialis Right whale
Tomilin (1967) records the right whale from Bermuda, and Moore (1953) lists it as one of Florida's marine mammals. Feeding is presumably concentrated in the summer and to the north of its range. No interaction with fisheries is therefore likely in area 31. The population in the western Atlantic is unknown, but unlikely to be more than a few hundred.
Balaenoptera physalus Fin whale
Tomilin (1967) states that this species is rare in the tropics, whilst Jonsgaard (1966a) states that it occurs as far south as 29°N off Florida. Interactions are unlikely in area 31 as this species is hardly ever seen there, and feeds mostly in more northern regions. (Tomilin 1967).
Balaenoptera musculus Blue whale
The southerly limit of the winter migrations of the Atlantic stock are unknown, but Jonsgaard (1966a) states that this is at least as far south as Atlantic city. Numbering only a few hundred in the North Atlantic, at most, this species represents no threat to fisheries at present, eating only pelagic crustacea, principally Thysancessa inermis, in the North Atlantic, and according to Tomilin (1967), no fish.
Balaenoptera acutorostrata Minke whale
Rarely recorded in area 31, Moore and Palmer (1955) state that at least 4 are recorded as having stranded in Florida until then, as far south as 25°N. Although the most Ichthyopagous of baleen whales, there can be little chance of any interaction with fisheries in area 31, due to their scarcity in this region.
Balaenoptera borealis Sei whale
Jonsgaard (1966a) reports them as far south as Mexico and Florida, and Erdman et al (1973) also report this species from the north east Caribbean, Mead (1977) provides a comprehensive list of records of this species in the area. According to Tomilin (1967) they are known to eat fish, but are best adapted to eat small pelagic crustacea, notably Calanus spp. in the North Atlantic. Although more warmth loving than B. physalus, they are still seen only very infrequently in area 31 and hence are unlikely to interact with fisheries.
Balaenoptera edeni Bryde's whale
A more tropical whale than other baleen species; Jonsgaard (1966a) reports this species was caught in Grenada in the 1920's. Hershkovitz (1966) also reports it from the Caribbean, and Payne (1979) from the Gulf of Mexico; it is, however, missing in Moore's (1953) list of species in Florida. Gambell (1977) suggests there may be a resident population in the area. The population size is unknown, but as the food is known to include commercial fish species elsewhere, some degree of competition with fisheries may occur here.
Megaptera novaengliae Humpback whale
This species regularly migrates to the Caribbean, to a number of breeding sites in the winter (as far south as Grenada). Hunted there by Yankee whalers in the last century, (Townsend 1937) this practice is continued on a very small scale by whalers in Grenada, though, this fishery appears to be dying out, (Caldwell & Caldwell 1975). Winn et al (1975) estimate the population in the Caribbean at between 785 and 1157, a great increase in the last 60 years. Humpbacks do not appear to feed in the winter or at least only to a very small extent (see eg. Mackintosh 1965 and Chittleborough 1965), so no interaction is likely with fisheries.
Mesoplodon densirostris Blainville's beaked whale
Again, according to Moore (1966) this species may inhabit the central Southern North Atlantic, straying to North America. Gunter (1955) records a specimen stranded in Padre Island, Texas, in 1946 and Caldwell and Caldwell (1971b) record one from Florida. Moore (1958: not seen) also records one from the Bahamas.
Mesoplodon europeaus Gervais' beaked whale
According to Moore (1966), this species probably inhabits the Antillean region and the Gulf of Mexico, straying northward along the Gulf Stream. Rankin (1953) reported 2 specimens from Jamaica, and according to Leatherwood and Reeves (1983) others have stranded in Florida, Texas, Cuba and Trinidad. No feeding data is available, but they are assumed to feed on squid.
Mesoplodon mirus True's beaked whale
Another deepwater species, which, according to Moore (1966), inhabits areas off the continental shelf of North America in the mid-Atlantic; it does not apparently stray into the Caribbean region, but has occasionally been stranded on the Atlantic coast of the United States. As with other beaked whales, squid is presumed to form the bulk of the diet.
Ziphius cavirostris Cuvier's beaked whale
Recorded throughout the area. Erdman (1962) reports one specimen from Puerto Rico, and cites Aguayo for another in Cuba. Moore (1953) lists it as present in Florida, and Erdman et al (1973) confirm its presence in the north east Caribbean. Caldwell et al (1971a) also record its capture in the St Vincent small whale fishery, and Caldwell et al (1971) report the species from Georgia and South Carolina. Despite this, like all other beaked whales, this species is not common, and according to Tomilin (1967) is normally found pelagically, although the number of strandings indicate that it does wander closer to shore. Erdman's (1962) specimen in Puerto Rico contained squid remains only, although Leatherwood and Reeves (1983) state that it also eats deepwater fish.
Physeter macrocephalus Sperm whale
Townsend's (1935) maps of the distribution of sperm whales clearly show enormous feeding grounds in the central Atlantic, and to a slightly lesser extent in the eastern Atlantic. Both of these grounds extend into the northern regions of area 31, and there are numerous other reports dotted around the Caribbean, West Indies and out to the “twelve forty” ground, centred at 12°N, 40°W. Taruski and Winn (1976) report sperm whales from Grenada to the Caicos banks in water deeper than 100 fathoms. Caldwell et al (1971a) noted that from October to March sperm whales might be caught in the St Vincent fishery. Erdman et al (1973) confirm the relative scarcity of sperm whales in the north east Caribbean in the summer. The sperm whale, according to Tomilin (1967), amongst many other, is essentially a squid eater, and so presumably any seasonal distribution is linked to squid availability. No estimates of the numbers of sperm whales in the area are available, but a figure in the thousands of animals at least visiting the area would not seem unreasonable. There has not been any interaction with fisheries, and unless a squid fishery is developed none seem likely in this area.
Kogia breviceps Pygmy sperm whale
Moore (1953), Gunter et al (1955) and Caldwell et al (1971) all attest to the presence of this species in the south eastern United States, yet there appears to be no evidence of its presence elsewhere in area 31. This is probably an artefact of its rarity. Tomilin (1967) states that it feeds principally on squid, although other items have been found in stomachs. No interaction is known nor seems likely.
Kogia simus Dwarf sperm whale
Probably even rarer than the preceding species and apparently recorded only from the eastern seaboard of the U.S. (Caldwell et al 1971), this species, like the last, is thought to feed on squid. No interactions are likely for the same reasons as above.
Steno bredanensis Rough-toothed dolphin
Recorded from Georgia, USA (Richardson 1973), Florida (Moore 1953) and also found in the St Vincent fishery by Caldwell et al (1971a). Payne (1979) also records 3 stranding incidents in the Gulf of Mexico, one involving 16 animals which were shown to have fed on pelagic octopi. These appear to be the only records of this animal. Once again interactions are unknown and unlikely due to its rarity and the absence of intensive cephalopod fisheries.
Sotalia fluviatilis Tucuxi
Found in the river systems of Venezuela and Guiana, and in the shallow seas around the coast of north eastern South America. They feed on catfish, other fresh water fish and crustaceans (Mitchell 1975). Bruyns (1971) cited in Mitchell (1975a) states that they are held in high esteem and are not hunted, but Best and da Silva (1984 in press) record the frequent incidental capture of this species in the Amazon. Presumably such captures occur in other parts of the range also. The population size is unknown.
Peponocephala electra Melonheaded whale
Only rarely recorded in area 31 this is an uncommon species worldwide. Caldwell et al (1976) found it in St Vincent, where they discovered fish otoliths, squid beaks, two isopods, and a very large red shrimp. No interaction with fisheries is known or likely.
Feresa attenuata Pygmy killer whale
Caldwell and Caldwell (1971a) record the first Caribbean occurrence of this species in the St Vincent fishery. James et al (1970) also report the first record from the Gulf of Mexico, and refer to another in Costa Rica, while Caldwell and Caldwell (1975a) describe a fourth record from Florida. This is an apparently rare species, with only a dozen or so records from around the world, although Pryor et al (1965) found a school of more than 50 near Hawaii. No interaction is known and none is likely due in part at least to the paucity of records of this species.
Psuedorca crassidens False killer whale
Odell et al (1980) describe a recurrent mass stranding in Florida and the Dry Tortugas, and Caldwell et al (1971a) found this species amongst those caught at St Vincent. Tomilin (1967) states that it eats squid and fish and is usually found far from coasts, though it may come closer to shore following cephalopods. Odell et al (1980) found that captive specimens ate mackerel, herring, smelt and some squid, and Watson (1981) reports seeing this species eating bonito. As yet no conflict is reported with this species, but the fact that it does eat commercially important fish makes a future conflict somewhat more plausible than with previously mentioned species in this area.
Orcinus orca Killer whale
This species has been recorded from Florida (Moore 1953) and St Vincent (Caldwell et al 1971a) where it has appeared in the whale catch. Numbers are unknown, but it does not appear to be common. Food is known to include gregarious fish and marine mammals, though Caldwell et al (1971a) also report turtles as a food item. This species does not apparently appear in large numbers or close to the shore as it does in Norway, and so no conflict with fisheries has been reported nor is one likely, given the catholic diet and apparently low density of this species in this area.
Globicephala macrorhynchus Short-finned pilot whale
Widely distributed throughout the region, this is the main species caught in the St Vincent fishery. Kritzler (1952) reporting on the mass stranding of 48 individuals, and subsequent captivity of 4 in Florida, states that squid is their main food. No interaction with fisheries is known at present, nor likely. The population size is unknown, but they are presumably not rare.
Lagenodelphis hosei Fraser's dolphin
The only record in area 31 appears to be that of Caldwell et al (1971a) in St Vincent. Leatherwood and Reeves (1983) state deepwater fish, crustacea, and squid are eaten. Conflicts are unknown, and unlikely.
Tursiops truncatus Bottlenose dolphin
This species is also very numerous in this area and is perhaps the most noticeable as it is chiefly a coastal species, wandering as far as the edge of the continental shelf. Moore (1953) describes it as common in Florida and it is also reported over much of the rest of the Caribbean. Payne (1979) states that 83% of its diet in the gulf of Mexico is mullet, and Shane (1980) adds a number of other demersal and neritic species. Leather-wood (1979) cites Cato and Prochaska (1976) as stating that Tursiops damages nets and catch in Florida to the tune of $0.5 million a year. They estimated the population of Tursiops in the area to be around 5000, but Leatherwood (1979) found the population to number around 500. Caldwell and Caldwell (1971) report this species both in the St Vincent fishery and as caught incidentally in beach seine nets in the southern Caribbean. Leatherwood and Reeves (1982) provide a comprehensive account of other minor interactions with fisheries. There are probably more interactions between this species and fishermen which are not recorded.
Grampus griseus Risso's dolphin
Tomilin (1967) describes this species as rare but widespread in warm and temperate waters. There are few obvious references to it in area 31 although Caldwell et al (1971b) record it at St Vincent. According to Tomilin (1967) it lives mainly or solely on squid, diving deep and long. No conflict is reported or likely.
Stenella longirostris Spinner dolphin
Recorded in area 31 by Moore (1953), Erdman et al (1973), and many others. This species is one of the main victims in the incidental dolphin take in the tropical east Pacific. It is most common in deepwater and as Caldwell and Caldwell (1971) point out, any tuna seining developed in this area may well be responsible for incidental mortality to this species. There are no abundance estimates but is is presumably fairly common.
Stenella coeruleoalba Striped dolphin
Odell and Chapman (1976) describe this species from Florida where it had fish otoliths in its stomach. Tomilin (1967) states that it is rare, but Leatherwood and Reeves (1983) describe it as widespread, and state that it feeds on small mesopelagic fish as well as shrimp squid. Like the last two species it too has been caught in the purse seine fishery for tuna in the Pacific, and hence may be susceptible if such a fishery were to develop in this area.
Stenella species Spotted dolphins
Moore (1953) lists Stenella attenuata as one of Florida's marine mammals. This is the species which has suffered most in the nets of the tuna fishery in area 77 and unlike the preceeding two species, it feeds in the surface layers on fish, as well as some squid. Payne (1979) records Stenella plagiodon as the most common Stenella species in the Gulf of Mexico. Siebenaler and Caldwell (1956) suggest that this species feeds on pinfish and squid, presumably on the surface. Like the other Stenella species, these too are vulnerable if tuna seining operations expand, using dolphin schools as markers for tuna fish.
Stenella clymene Clymene dolphin
A little known spinner dolphin, recorded on a few occasions in this area (Perrin et al 1981). Its status is unknown, but presumably its apparent rarity does not preclude it from incidental mortality in any projected tuna seine fishery.
Delphinus delphis Common dolphin
Moore (1953) and Erdman et al (1973) both describe this species from the north of area 31, and it seems to be quite common at sea there, although it may be rarer in the south. Like the Stenella species this too is caught in tuna nets being a pelagic schooling species. Tomilin (1967) describes it as a typical ichthyophagous species, feeding far from shore on smallish fish such as herring, anchovy and pipefish, as well as carangids, mullets and many others. Leatherwood and Reeves (1983) state that they feed in the deep scattering layer on fish and squids. This species too may be vulnerable to expanded pelagic fisheries in the area, although no conflicts are reported as yet.
Inia geoffrensis Boutu
Known to occur, according to Hershkovitz (1966) in the river systems of Colombia and Venezuala, this species is apparently fairly common in parts of its range although Leatherwood and Reeves (1983) believe that increasing numbers are being killed in recent years, but catch data are unavailable. The food is thought to consist of characins and catfish, two of the most plentiful groups of fish in South American fresh waters. There is some incidental catch of this species in gill net fisheries in the Amazon (see area 41) so presumably they may also be caught in the Orinoco and other rivers flowing out to area 31. However there are no data on this.
Zalophus californianus Californian sea lion
This species is reported from Georgia and South Carolina by Caldwell et al (1971), having escaped from captivity. Feral sea lions are not known to have bred, but if a breeding population became established, it might quickly become a nuisance locally.
Phoca vitulina Harbour seal
May wander as far south as Georgia and Florida, but in insignificant numbers.
Monachus tropicalis Caribbean Monk seal
Presumed extinct.
Trichechus manatus Caribbean manatee
Shane (1983) estimates the population in Florida to total around 1 000. Elsewhere the population size is unknown. In Florida at least there is a high mortality associated with boat collisions with this species (FAO 1978). Presumably a large number of these boats are fishing boats, commercial or recreational, and in this respect manatees may be said to be interacting with fisheries. Manatees are also caught accidentally in gill nets in the rivers in northern South America, (Lavigne pers. comm.), but there appear to be no detailed data on this. As this species is entirely herbivorous, competitive interactions for food are unlikely.
Information on marine mammals in this region is extremely patchy. Extensive information exists for the more northerly parts, but, particularly off the coast of northern South America the data are more scarce. Of the 33 or so species of marine mammal found in this area, 6 species of baleen whale probably do not feed in these waters, and are anyway not common. Bryde's whale may feed on small shoaling fish, such as menhaden and possibly sardinellas. At least another ten species are thought to feed mostly or entirely on cephalopods, and do not at present interact with fisheries, and the diet of another 6 uncommon species is unclear.
Of the remaining species, the two predominantly freshwa er species eat a variety of fish and crustacea, some of which are also fished for commercially. The bottlenose dolphin is known to feed on mullet and other neritic species. All of the delphinid species in this region may feed on small pelagic shoaling fish, which may include some commercial species as well as myctophids and other non-commercial species. One is herbivorous.
