2.4 FAO Statistical Area 34 - West Africa
2.4.1 Survey data
22.214.171.124 West African Slope
Golovan (1978) reviewed the results of several Russian research surveys carried out on the continental slope of West Africa between 32° and 4° N. and at depths between 500 and 1920m. He recorded one species of the family Chlamydoselachidae, six species of the family Scyliorhinidae, 15 species of the family Squalidae and one species each of the families Scymnorhinidae and Echinorhinidae.
Research surveys on the continental slope off West Africa using an epibenthic sledge and a small otter trawl indicated the presence of Apristurus spp., Etmopterus princeps, Etmopterus spinax, Centroscymnus coelolepis and Centroscymnus crepidater (Merrett and Domanski 1985).
126.96.36.199 Canary Islands
Ublein et al. (1998) give details of the depth distribution of Galeorhinus galeus, Squalus megalops, Galeus melastomus, Centrophorus lusitanicus, Centrophorus granulosus, Etmopterus pusillus, and Deania calcea from longline surveys around the Canary Islands. The squalene oil content of the livers of the following deep-water sharks caught in a longline survey of the Canary islands has been determined: Centroscymnus coelolepis, Centroscymnus cryptacanthus, Centrophorus squamosus, Centrophorus lusitanicus, Deania histricosa, Deania profundorum, and Etmopterus princeps (Hernandez-Perez et al. 1997).
2.4.2 The fisheries
Muñoz-Chápuli (1985) has analysed the catches of demersal sharks from trawlers operating between about 27°–37°N off the Moroccan coast and around the Canary Islands. The species present and their abundance in each of three areas are shown in Table 32 Area A is between latitudes 27°– 31°N and includes the Canary Islands, area B is the Moroccan Coast between 31°–34°N and area C is between 34°–37°N). Only Squatina aculeata and Mustelus asterias were not found deeper than 200m. Otherwise there are apparently no published statistics that would enable deep-water demersal shark landings to be identified separately from other coastal and pelagic sharks.
2.5 FAO Statistical Area 47 - Southeast Atlantic
Compagno et al. (1991) have provided a detailed account of the distribution of offshore cartilaginous fishes of the west coast of southern Africa. Depth distributions and an indication of abundance from survey data are given for 32 species, most of which are truly demersal species. Sharks are undoubtedly caught as a bycatch of the hake fisheries and Compagno et al. (1991) have shown that the diversity indices for cartilaginous fishes are much lower at depths and areas where hake dominate the biomass.
2.6 FAO Statistical Areas 48, 58 and 88 (Southern Ocean - CCAMLR areas)
The only elasmobranch fishes included in the CCAMLR reporting system are the rays. There are only three known sharks, Lamna nasus, Somniosus pacificus and Etmopterus sp. (Kock et al. 1985, Stevens Pers. Comm.). These were reported at depths between 100 and 500m off the Kerguelen Islands and elsewhere in the Southern Ocean.
On the slope of the Kerguelen shelf, rays, mainly Bathyraja eatoni and B. irrasa, are a common bycatch from the long-line fishery and sometimes also occur as bycatch in the trawl fishery. Three species of sharks are commonly recorded in the fishery: Lamna nasus in the icefish fishery (shelf depth of 150–250m, Somniosus microcephalus in the Patagonian toothfish fishery, both longline and trawls, from the slope and deepsea, from 300 to 900m and probably deeper. A more rare shark, Etmopterus of granulosus is taken in the deep-sea longline fishery (1000 – 1200m). In the Crozet Island fishery a ray, Raja taaf, is a common bycatch in the longline fishery. The sharks appear to be uncommon but S. microcephalus has been recorded as bycatch from the longline fishery.
2.7 FAO Statistical Area 513 - Western Indian Ocean
Much work on the deepwater elasmobranch resources of the Indian Ocean has been done be research vessels of the Southern Scientific Research Institute of Marine Fisheries, Kerch, Ukraine and not all the information available at that institute in the YugNIRO database has yet been published. As is indicated, the information in this section generally refers to depths greater than 450m.
In the northern Gulf of Aden not less than 10 species of deepwater sharks occur. Among these are:
Heptranchias perlo (Hexanchidae) at depths of 490–530m; a common species
Etmopterus pusillus (Dalatiidae) at depths of 450–600m, rare
Centrophorus granulosus (Centrophoridae) 410–605m, common
Deania profundorum (Centrophoridae) 470–600m, common
Echinorhinus brucus (Echinorhinidae) 405–430m, rare
Pristiophorus sp.n. (Pristiophoridae) 465–600m, rare
Halaelurus hispidus (Scyliorhinidae) 410–605m, very common
Eridacnis radcliffei (Proscylliidae) 410–470m, very common
lago omanensis (Triakidae) 405–605m, common
lago sp.n. 470–485m, rare
In the Sokotra Island region 12 species of deepwater sharks have been recorded:
Etmopterus pusillus (Dalatiidae) at depths of 490–500m, a rare species
Centrophorus granulosus (Centrophoridae) 400–710m, common
Deania profundorum (Centrophoridae) 490–710m, common
Squalus megalops (Squalidae) 400–555m, rare at these depths
Pristiophorus sp.n. (Pristiophoridae) 400–710m, rare
Halaelurus hispidus (Scyliorhinidae) 400–710m, common
Apristurus sp. 700–710m, rare
Cephaloscyllium sp. 405–442m, rare
Eridacnis radcliffei (Proscylliidae) 400m, common
Eridacnis sinuans, 400–555m, common
lago sp.n. (Triakidae) 400–500m, rare
Alopias superciliosus (Alopiidae) 400m, rare at this depth.
3 This section kindly contributed by Dr Sergei I. Usachev, Southern Scientific Research Institute of Marine Fisheries, and Oceanography, Crimea, Ukraine and includes material from Gubanov (1993).
There are no fisheries targeting deepwater sharks in these areas except for Alopis superciliosus. Deepwater sharks are generally taken by bottom trawls as bycatch of shrimp and lobster fisheries. No recent information exists about the fisheries in these areas.
Detailed data on species composition and depth ranges of deepwater sharks of Walters Shoals in the Southwestern Indian Ocean were obtained by the Russian R.V. Vityaz expedition to the western Indian Ocean in 1988–1989 and are available in Parin, Sagaidachny and Shcherbachev (1993). They describe the following elasmobranch fauna:
Centroscymnus coelolepis (Squalidae) captured at depths of 1150–1260m
Centroscymnus crepidater, 1060–1080m
Centrosymnus owstoni, 1175–1760m
Dalatias licha, 775–1260m
Deania calceus, 930–1030m
Deania profundorum, 775–1030m
Deania quadrispinosa, 600–1360m
Etmopterus brachyurus, 650–950m
Etmopterus baxteri, 970–1200m
Etmopterus granulosus, 940–1400m
Etmopterus lucifer, 785–1115m
Etmopterus molleri, 655m
Etmopterus pusillus, 928–940m
Squalus mitsukurii, 250–775m
Squalus cf mitsukurii, 650–660m
Zameus squamulosus, 1100–1230m
Apristurus profundorum (Scyliorhinidae) 1030–1110m
Apristurus cf. Platyrhynchus, 1090–1100m
Apristurus sp.n., 1340–1560m
Halaelurus sp.n., 855–1200m
Halaelurus canescens 830–1120m
Parmaturus sp., 1500–1560m
2.8 FAO Statistical Area 61 - Northwest Pacific
Japan is historically one of the world's most important shark fishing nations, although landings have declined in recent years (Rose 1996). In 1993 the total catch was 25673t, of which 77% was taken by tuna longliners in the distant, offshore and coastal fisheries. In the CITES report, no mention is made of targeted deep-water fisheries or of bycatch of deep-water fisheries. No detailed data on species composition is available from Japanese statistics after 1968 (Bonfil 1994). Bonfil names many of the sharks of importance in Japan, but no deep-water demersal species is included.
Yano and Tanaka (1984) state that deep-water sharks have been exploited in Suruga Bay (Japan) since the 1940s for the squalene in their liver oil. Most of them belong to the genera Centroscymnus, Centrophorus and Deania. Some aspects of the distribution and biology of Centroscymnus coelolepis and Centroscymnus owstoni have been described by Yano and Tanaka (1984, 1988). The vertical distribution and feeding habits of Etmopterus lucifer, Etmopterus unicolor and Centroscyllium ritteri from the continental slope off Chosi (Japan) have been described by Baba et al. (1987).
In the 1960s and 1970s a major international fishery developed on the southern Emperornorthen Hawaiian seamounts for the pelagic armourhead (Pseudopentaceros wheeleri), which undoubtedly affected many other species (Wilson and Seki 1994). Probably one of the most important bycatch species was the demersal shark, Squalus mitsukurii. In a survey of the southeast Hancock Seamount between 1985 and 1988, Wilson and Seki (1994) noted a significant decline in CPUE and estimated that about 80% (±55%) of the initial population had been removed by fishing.
2.9 FAO Statistical Area 81 (part) - New Zealand
2.9.1 The deep-water demersal shark species
Cox and Francis (1997) have described the sharks of New Zealand.
2.9.2 Survey data
In a survey of the deep-water fish resources off the North Island of New Zealand, the following deepwater shark species were recorded: Chlamydoselachus anguineus, Heptranchias perlo, Centrophorus squamosus, Centroscymnus plunketi, Centroscymnus owstoni, Centroscymnus coelolepis, Centroscymnus crepidater, Dalatias licha, Deania calcea, Etmopterus baxteri, Etmopterus lucifer, Etmopterus sp. A, E. cf. pusillus, Oxynotus bruniensis, Odontaspis ferox, Mistukurina owstoni, Apristurus spp., Parmaturus sp., Gollum attenuatus and Pseudotriakis microdons (Clark and King 1989).
In a survey for orange roughy in southern New Zealand waters, the following species were recorded: Centrophorus squamosus, Centroscymnus coelolepis, Centroscymnus crepidater, Centroscymnus owstoni, Centroscymnus plunketi, Centroscymnus Sp. A, Dalatias licha, Deania calcea, Etmopterus baxteri, Etmopterus lucifer, Apristurus spp. A, B, C and D (Clark and Tracey 1992). Four of these were amongst the top ten by weight of all fish caught during the survey: E. baxteri, C. plunketi, C. crepidater and C. owstoni.
2.9.3 The fisheries
Bonfil (1994) reported that between 1989 and 1992, about 4% of the elasmobranchs landed in New Zealand consisted of 13 species of deep-water sharks and at least three species of batoid. Because of the scarcity of information concerning the relevant stocks, effectively it is unknown if New Zealand's deepwater resources of elasmobranchs can withstand the current fishing pressure (M. Francis, NIWA, Wellington, Pers. Comm).
King and Clark (1987) considered that the New Zealand sharks Deania calcea, Etmopterus baxteri, Dalatias licha, Centrophorus squamosus, Centroscymnus plunketi, Centroscymnus owstoni, Centroscymnus coelolepis and Centroscymnus crepidater were of large enough size and sufficiently abundant to be of commercial interest. Deania calcea tended to be the most abundant species in the north, E. baxteri in the south and Centroscymnus in the centre. The livers of all eight species can be used for oil and squalene. The squalene content was highest in D. calceus, C. squamosus and D. licha. A potential problem was that the mercury levels in the small number of samples analysed were above the New Zealand permitted levels.
In a recent paper on New Zealand shark fisheries (Francis in press), Dalatias licha is recorded as an important bycatch that is landed for its flesh. Landings of Deania calcea peaked in the late 1980s and have been low ever since. This may have been caused by changes in the markets for the liver oil, but no data are available for exports except for 1985, when 23t were exported to Japan. Table 33 gives the reported landings data for New Zealand species that may be considered as deepwater, i.e. characteristically taken as depth >200m (Francis in press). A decline had been evident since the peak fishing year of 1994–95, mainly in the landings of ghost sharks (Hydrolagus spp).
Further information on the potential value of shark liver oils is given by Summers (1987) and Summers and Wong (1992).
2.10 FAO Statistical Areas 57, 71 and part 81 (Australian waters)
2.10.1 The deep-water demersal shark species
Australia has a diverse shark fauna, including many deep-water demersal species (Last and Stevens 1994). Many deep-water species, especially of the genera Etmopterus and Apristurus, have not yet been described.
2.10.2 Survey data
Newton and Klaer (1991) provide the following provisional list of sharks from their deepwater survey of the slopes of the Great Australian Bight: Heptranchias perlo, Apristurus spp., Cephaloscyllium nascione, Galeus, boardmani, Centrophorus moluccensis, Centroscymnus owstoni, Centroscymnus coelolepis, Dalatias licha, Deania calcea, Deania quadrispinosa, Deania sp., Etmopterus brachyurus, Etmopterus lucifer, Etmopterus sp., Oxynotus bruniensis, Squalus acanthias and Squalus mitsukurii. In a survey of the upper slope of the southeastern Australian continental slope, Graham et al. (1997) caught 25 species of shark. The most abundant were Squalus megalops, Centrophorus moluccensis, Squalus mitsukurii, Centrophorus harrissoni and C. uyato.
|1986– 87||1987– 88||1988– 89||1989– 90||1990– 91||1991– 92||1992– 93||1993– 94||1994– 95||1995– 96||1996– 97|
2.10.3 The fisheries
The elasmobranch fisheries of Australian waters are small but quite well-documented (Bonfil 1994). Almost all are coastal or offshore pelagic sharks and area 57 accounts for most of the landings. Rose (1996), quoting Bentley (1996), reports that Centrophorus uyato and Squalus mitsukurii and, to a lesser extent Centrophorus moluccensis and C. harrissoni, have recently begun to be exploited for their liver oil off southern Australia.
Deep-water dogfish (mainly Deania calcea, Centroscymnus owstoni, Centroscymnus coelolepis, Centroscymnus crepidater and some Etmopterus and Apristurus spp.) are taken mainly as bycatch in the orange roughy fishery (Stevens Pers. Comm). Little has been published, other than papers on their taxonomy and the squalene oil (Deprez et al. 1990). The flesh of some species is not utilised because of its high mercury content (Last and Stevens 1994). Stevens also notes that there is some targeting of other less deep-living species (Centrophorus spp.) both for meat and liver oil and that these species also figure in bycatch from trawl fisheries. Squalus megalops and Squalus mitsukurii are common on the upper slopes and small quantities are marketed. The latter is sold under the name of 'greeneye dogfish' (Last and Stevens 1994).
3. MANAGEMENT AND CONSERVATION
Deep-water fisheries have developed quite rapidly in recent years, both as a response to improved technology and the need to find new resources to replace over-exploited shallow-water fisheries. These deep-water fisheries can often develop rapidly and can be depleted long before any appropriate management action can be put in place. This situation is exacerbated by a basic lack of knowledge of the fish and their habitat. Only in two areas is our knowledge sufficiently advanced to enable some discussion of the problems as they relate to deep-water sharks. In Australia and New Zealand the surveys associated with the orange roughy fisheries have yielded valuable information on the fish assemblages, including the sharks. There is also information on landings and estimates of discards. In the northeastern Atlantic knowledge of the deep-water ecosystem has advanced considerably in the last few decades. The developing fisheries have been quite well documented by the NATO Advanced Research workshop (Hopper 1995), the ICES Study Group on the Biology and Assessment of Deep-sea Fisheries Resources (Anon. 1995b, 1996b, 1998b) and the unpublished reports of the EC FAIR Deep-fisheries Project (95–655) Developing deep-water fisheries: data for the assessment of their interaction with and impact on a fragile environment. This section will use these investigations to illustrate the problems of management and conservation of deep-water shark resources.
The first major difficulty for most statistical areas is that there is a lack of basic data on landings of deep-water demersal sharks. The term 'sharks various', or similar terms, includes a wide range of shelf and oceanic pelagic and demersal sharks. Separating the various groups from reported landings is difficult. Some estimates can be made using a knowledge of the fisheries and in particular the fishing gear being used. However, if there are several types of fisheries in operation, as off southwest Ireland (see Chapter 1), then it becomes difficult. It is probable that in assessing the relative importance of shark species to fisheries, the deep-water catsharks (Scyliorhinidae) and many small, deep-benthic and oceanic dogfish (Squalidae) fall into the category of 'minimal catch species' (Compagno 1990). However, although the landings may be minimal in terms of all shark species, the discarded catch in the new and developing fisheries on the continental slopes and seamounts is probably quite considerable. Another problem with landings data is that they do not fully take into account the landings of shark products, such as livers or fins (Rose 1996).
If landings data are to have any use for assessment purposes, it is essential that the species are identified correctly. This in turn pre-supposes that all species are adequately described. Unfortunately, this is not the case and even in the northeastern Atlantic, with a history of over 100 years of research, certain genera such as Apristurus and Centrophorus are in urgent need of revision. Even for a fishery biologist, many of the deep-water sharks are difficult to identify. Within the ICES area, 27 different species of demersal shark were recognised by the ICES Study Group on Elasmobranch Fishes (SGEF) (Anon. 1997a). The Study Group also compiled basic biological information on each of the species. It is therefore not surprising that landings dataof deep-water demersal sharks are almost always in grouped categories.
In the longline fisheries of Portugal, some of which target deep-water sharks (see 188.8.131.52), a variety of species are landed. In an effort to check the validity of the official landing statistics for sharks, a market sampling programme was carried out by Institute de Investigaçãdas Pescas e do Mar (IPIMAR) under the auspices of the EC FAIR Deep-fisheries Project. The results showed that the identifications by the fishermen were reasonably accurate. Unidentified sharks only accounted for about 7% and erroneous identification were less than 3% (EC FAIR 95–655, unpublished report).
In the bottom trawl fishery to the west of the British Isles two species, Centroscymnus coelolepis and Centrophorus squamosus, account for most of the landings. The main market is France, where they are collectively known as ‘siki’. The landings of siki have increased considerably during the 1990s, but the information on the relative proportions of the two species is not obtainable from the statistics. Sampling of the landings at the French port of Concameau by the Laboratoire de Biologic Marine du Collège de France has shown that the relative proportions of the two species can vary quite considerably between season and years (EC FAIR 95–655, unpublished report).
ICES ACFM (Advisory Committee on Fisheries Management) has consistently recommended that landings should be recorded at species level (Anon. 1997b). However, one of the problems has been the lack of standard three-digit identifier codes. The ICES SGEF report of 1997 recommended a list of species for changes and additions to the “FAO STATLANT codings (Anon 1997a). These codings are given in full in Anon (1998a), which also recommends changes to the common names used for Galeus spp. and Apristurus spp. Table 34 lists the codings appropriate to the deep-water demersal sharks. While common names have some obvious uses, they can also cause problems. Many of the deep-water species have global distributions and even in the same language there are numerous common names. At the start of the EC FAIR Deep-fisheries Project all participants agreed to use scientific names in all their reports.
|3 - alpha identifier||Species (scientific name)||Species (common name)|
|SHO||Galeus melastomus||Blackmouth catshark|
|SYC||Scyliorhinus canicula||Small-spotted catshark|
|PTM||Pseudotriakis microdon||False catshark|
|SOR||Somniosus rostratus||Little sleeper shark|
|GUP||Centrophorus granulosus||Gulper shark|
|CPU||Centrophorus uyato||Little gulper shark|
|GUQ||Centrophorus squamosus||Leafscale gulper shark|
|CPL||Centrophorus lusitanicus||Lowfin gulper shark|
|ETX||Etmopterus spinax||Velvet belly|
|ETP||Etmopterus princeps||Great lanternshark|
|DNA||Deania spp.||‘Deania’ dogfishes|
|DCA||Deania calcea||Birdbeak dogfish|
|CYO||Centroscymnus coelolepis||Portuguese dogfish|
|CYP||Centroscymnus crepidater||Longnose velvet dogfish|
|CYY||Centroscymnus cryptocanthus||Shortnose velvet dogfish|
|SYO||Scymnodon obscurus||Smallmouth knivetooth dogfish|
|SYR||Scymnodon ringens||Knivetooth dogfish|
|SCK||Dalatias licha||Kitefin shark|
|CFB||Centroscyllium fabricii||Black dogfish|
|OXY||Oxynotus centrica||Angular roughshark|
|OXN||Oxynotus paradoxus||Sailfin roughshark|
The landings of deep-water demersal sharks often account for only a small part of the total shark catch. Those brought to the surface and subsequently discarded are generally so badly damaged and stressed by changes in pressure and temperature that few would survive. The discarding of a significant proportion of the top predators will have important effects on the ecosystem and for biodiversity. In the northeastern Atlantic there is an almost unique situation where there are survey data which pre-date the commercial fishery. There have also been several investigations of discarding in the current fishery. For this reason, it is worthwhile considering this area as an example of some of the problems. The following is a summary of the present status of knowledge.
The continental slope lying to the west of Scotland and Ireland is of considerable interest in terms of deep-water fish and fisheries. Some of the earliest descriptions of deep-water fish were made in this area (Murray and Hjort 1912) and the cruises of the Helga at the end of the 19th Century did much to describe the fauna, including some of the deep-water sharks (Holt and Byrne 1910). There were relatively few surveys in the early part of the 20th century and most simply listed the catch from surveys extending into deeper water for species such as hake (Merluccius merluccius). The situation changed in the 1970s when the loss of fishing opportunities for traditional species resulted in countries such as the United Kingdom and Germany becoming interested in the potential for exploiting deepwater demersal species. In 1973 and 1974 the UK Ministry of Agriculture Fisheries and Food carried out a series of four research vessel and two charter vessel cruises to explore the potential of the deepwater continental slope at depths between about 500 and 1200m. A report of some of the main features of these surveys was published (Bridger 1978). The UK carried out a further survey in 1978. Recognising the importance of these surveys as a baseline for the fisheries that have subsequently developed in these areas, a proposal to work up and archive the logbook data from these surveys was funded by the European Commission (Gordon and Swan 1997). At about the same time, the Institut fur Seefischerei (ISH) in Hamburg also began a series of TIFI cruises between 1974 and 1986. Although some of the data on the teleost species was published (Ehrich 1983), the sharks were not considered to be of commercial interest and were excluded. However, some data on the distribution, abundance and biomass of the sharks can be obtained from an analysis of the data from eight of the cruises (Ratz 1984). It has also been recognised that these surveys represent a valuable resource on the status of the fish assemblages prior to the current exploitation. These data are presently being compiled and analysed as a contribution by ISH to the EC-funded Fair Deep-fisheries Project.
In addition to these surveys which covered a wide geographical area, there have been others which have concentrated on seasonal sampling of more discrete areas. Between 1975 and 1992 the Scottish Association for Marine Science (SAMS) investigated the deep water demersal fish of Rockall Trough between about 55° and 57°N (Gordon and Bergstad 1992; Gordon and Duncan 1985; Gordon and Swan 1993) as part of a more detailed study of the area (Mauchline 1986). The depth range covered by these surveys was from 245 to 2996 m, which made it possible to define the total depth range of all the shark species. Another similar survey was carried out jointly by SAMS and the Institute of Oceanographic Sciences (IOS) in the Porcupine Seabight between 1979 and 1983. General descriptions of the fish populations are given by Merrett et al. (1991a,b). Further information on the deep-sea benthic programme is provided by Jackson et al. (1991) and Rice et al. (1991).
The data on the depth distribution, abundance and biomass by area and depth from these surveys have been summarised by Gordon and Swan (1997b). These data, to some extent, represent the status of the stocks prior to the current exploitation of the deep-water fish populations.
The recent growth of deep-water fishing in the Atlantic began in the 1960s when the USSR and other eastern European countries began to exploit species such as roundnose grenadier (Coryphaenoides rupestris) off Canada at depths down to about 900m. The fishery developed rapidly, with landings peaking at almost 84 OOOt in 1971. The fishery also extended to the eastern North Atlantic (Reykjanes Ridge and Hatton Bank, east of the Rockall Plateau) and the peak catch of over 30 000t of roundnose grenadier was landed in 1975. These fisheries have declined to a much lower level, mainly for political and economic reasons. In the Rockall Trough deep-water fishing began in the early 1970s when first German and then French vessels began to exploit blue ling (Molva dypterygia) at depths down to about 800m. Landings of other deep-water species did not begin until about 1989 when the French fishing industry began to develop markets for species such as roundnose grenadier, black scabbardfish (Aphanopus carbo) and squalid sharks. It is probable that the blue ling fishery began as a targeted fishery on spawning aggregations and the bycatch of other species might have been minimal. However, as the fishery developed, it changed to a more multi-species fishery and it is likely that all the species that are now landed were discarded. As the market for these species and especially roundnose grenadier developed, the fishery moved into deeper waters (to about 1200m). In 1992 stocks of orange roughy (Hoplostethus atlanticus) were found and exploited, thus extending the fishery into even deeper waters (down to 1900m) (Charuau et al. 1995). Scottish trawlers also fish in the deep water, although most target monkfish (Lophius piscatorius) at depths down to about 800 m. In all these fisheries different species of demersal sharks are caught, depending on depth and area. They are either discarded whole, or discarded after removing the liver, or landed. Only two species, Centroscymnus coelolepis (Portuguese dogfish) and Centrophorus squamosus (leafscale gulper shark) are generally landed for human consumption under the name of ‘siki’ (see 3.2).
In addition to the bottom trawl fisheries, there also exist longline fisheries. Norwegian longliners traditionally fish for ling (Molva molva) and tusk (Brosme brosme) along the outer shelf and upper continental slope to the west of the British Isles. Experimental longline surveys in deep water have also been carried out by Norway (Stene and Buner 1991; Olsen 1995). The shark information from Stene and Buner (1991) has been summarised by Gordon and Swan (1997b) (Table 5).
Spain has a longline fishery for hake along the edge of the continental slope and the livers of deep-water sharks are retained. In some cases the carcass is also landed. Recently, there has been a targeted fishery for deep-water sharks in this area (Piñeiro et al. 1998).
The first study of discarding in the Rockall Trough resulted from Irish longline and trawl surveys (Connolly et al. 1996). The longline survey took place in November to December 1995 and the results are based on 17 valid sets between depths of 540 and 1224m. The trawl survey was carried out using a commercial trawler in November 1995. The trawl used was a commercial rockhopper trawl, with a 4.5m headline height and a wing spread of about 24m. The 100mm mesh codend was lined with a 10mm liner. In the trawl surveys the weight of the total catch was estimated from the average weight of a box and the species composition was recorded. The landings were recorded from the haul sheet as the number of boxes. The number of boxes of discards was also recorded and representative boxes were analysed. The weight of discards of each species was then expressed as the weight per tonne of roundnose grenadier landed.
The landings from the trawl were dominated by roundnose grenadier and Centroscymnus coelolepis. There was a wide range of discard species but the deep-water sharks, Deania calcea, Centrophorus squamosus, and Centroscymnus crepidater were among the dominant species. Table 35 shows the weight in kg of the sharks discarded per tonne of roundnose grenadier landed. The total discards of all species amounts to about 7530t per 8000t of roundnose grenadier landed. Shark discards comprise about 52% of the discards of all species.
|Shark species||Kg discarded per tonne roundnose grenadier landed||Tonnes discarded in 1995||Numbers discarded in 1995|
Only 12 species were caught by the longline and of these, six were sharks. The retained sharks were Centrophorus squamosus and Centroscymnus coelolepis which comprised, on average, 75% and 9% of the catch, respectively. The discarded species were Centroscymnus crepidater, Deania calcea, Etmopterus spinax and Galeus melastomus and they comprised about 4% of the total catch and 90% of the discards.
Investigations of discarding by the commercial French and Scottish trawler fleets have been carried out by the Scottish Office Marine Laboratory as a contribution to the EC FAIR Deep-fisheries Project (Blasdale and Newton 1998). Both fleets fish at depths down to about 900 m and only two species, Deania calcea and Centroscymnus crepidater, make a small contribution to the total discards. The mean discard rate for Deania calcea for both fleets was about 2kg/hr.
Also, as a contribution the EC Fair Deep-fisheries Project, IFREMER have carried out discard studies on French trawlers fishing in the Rockall Trough. The main emphasis has been on the roundnose grenadier but some information on other species, including the sharks, has been published (Dupouy et al. 1998). The shark data in terms of numbers of individuals landed and discarded in 1996 is shown in Table 36. The shark species most frequently discarded is Deania calcea.
Deep-water sharks can form a significant component of the discards in both the bottom trawl and longline fisheries. There are quite noticeable differences between the different studies, but this is to be expected as a result of the different areas and depths fished and the gear type used.
|Species||March 96||May/June 96||Sept. 96||Dec. 96|
|3 (0.0)||2(1.2)||4 (2.7)||8 (7.6)|
|1||7(4.9)||3 (2.1)||8 (6.6)|
Centroscymnus coelolepis +
|Centrophorus squamosus||49(93.7)||2(2.1)||8(13.2)||5 (4.6)|
In the commercial bottom trawl fishery, the codend mesh is generally 100mm stretched mesh. However, Kelly et al. (1998) have observed that there was little difference in the length frequency composition of roundnose grenadier obtained using a commercial codend and a research codend of 10mm, suggesting that the meshes are almost closed under the tensions on the trawl in fishing at great depth. Deep-water fish tend to have fragile skins and are not well endowed with mucus. It is probable that most fish, including sharks, which enter the trawl and subsequently escape suffer a high mortality. These escapees have sometimes been called ‘no catch discards’. Thus the total catch of fine-meshed research bottom trawls is probably a good indication of the fish assemblage that is removed by commercial trawling. However, there is a further complication caused by the selectivity of the trawl itself.
In research surveys in the Rockall Trough and Porcupine Seabight, particular emphasis was placed on comparing the catch composition obtained by using different bottom trawls (Gordon and Duncan 1985: Gordon and Bergstad 1992; Gordon et al. 1996; Merrett et al. 1991a). The small shrimp trawls fished on a single warp, which are often used in deep-water surveys, were particularly inefficient at capturing fast swimming species such as the sharks. The converging bridles ahead of the trawl probably serve to deflect these species out of the path of the net. In the commercial fishery only paired warp trawls are used. Little is known of the catching efficiency of these trawls, although it is likely that headline height may influence catches. Some evidence from studies of the diet suggest that Etmopterus spinax, Etmopterus princeps, Centroscymnus crepidater and Apristurus spp. may feed higher in the water column than Centroscymnus coelolepis, Centrophorus squamosus, Deania calcea and Centroscyllium fabricii (Mauchline and Gordon 1983). The French industry tend to use lighter trawls with high headline heights, whereas the Scottish vessels use so-called ‘scraper trawls’ of low headline height, specifically to target Lophius spp. Some significant differences in discards of teleost species were found between the two fleets (Blasdale and Newton 1998), but the discards of Deania calcea were not significantly different between the two fleets. However, these results may reflect the differences in the depths fished by the two fleets rather than in the design of the trawl. The recent trend towards the use of twin-rig trawling in deep water could cause changes in the shark bycatch. The disturbance in front of the trawl caused by the third towing warp could deflect sharks and other fast swimming species out of the path of the nets in the same way as a single warp trawl.
The depth fished is likely to have the greatest influence on the catch composition. In a multivariate analysis of all the trawl catch data in the Rockall Trough, Gordon and Bergstad (1992) showed that depth accounted for most of the variance, with gear type only second in importance. Table 1 shows quite clearly how the catch composition, abundance and biomass changes with depth in the Rockall Trough. This information is summarised diagrammatically in Figure 4. Similar results were obtained in a comparison of the above SAMS data and data from IFREMER surveys (Lorance, Pers. Comm.) To estimate the discarding of shark species, a knowledge of the depth of the target fishery is essential.
Depth distributions of deep-water sharks in the Rockall Trough.
The deep-water sharks are top predators and therefore readily take baited hooks. Longlining is therefore relatively unselective and can result in high discard rates (Connolly and Kelly 1996). If deepwater longlining were to increase in the northeastern Atlantic, the landings and discards might significantly increase, especially in some areas (Table 5).
3.4 Fisheries effects
Although there have been many surveys in the Rockall Trough, direct comparisons between the fish assemblages before and after the fishery are difficult because different gears have been used. In the commercial fishery trends in CPUE are also difficult to interpret because, as in any new and developing fishery, efficiency improves with experience. To overcome this problem, Lorance and Dupouy (1998) analysed the fleet in terms of vessel size, power and technological development. From this, they identified a fleet that had changed little as the fishery developed and used this to compare trends in CPUE for the target species. The results were used to calculate a CPUE index of abundance for the squalid sharks, Centroscymnus coelolepis and Centrophorus squamosus combined, which shows a reduction of approximately 50% between 1991 and 1996 (Table 16). It should be noted that although 1991 was taken as the starting point, these species were being caught and discarded in earlier fisheries for species such as blue ling. There is no information on the possible impacts of the fishery on the stocks of the discarded bycatch species.
The dramatic decline in the landings of Dalatias licha from the Azores (Anon 1998a) may be attributed to a high level of exploitation, but fluctuations in the price of liver oils may also contribute (Anon 1995a).
The Spanish longline fisheries which either target sharks or have sharks as a bycatch show considerable annual and seasonal fluctuations in the landings (Piñeiro et al. 1998). It is probable that many of these fluctuations are caused by changing conditions such as weather, price of liver oil, relative value of other species etc. It is therefore difficult assess the possible impact of the fishery on the stocks.
In New Zealand a study of the population changes associated with the orange roughy fishery on the Challenger Plateau by dark and Tracey (1994) found an estimated reduction in the biomass to about 20% of the virgin level. However, the biomass indices of the other bycatch species did not show the same trends between 1987 and 1989. The biomass of Centrophorus squamosus and Centroscymnus owstoni showed little change. A declining abundance was suggested for Deania calcea and Dalatias licha. There appeared to be no compensatory species replacement for orange roughy.
Graham et al. (1997) have compared the catches of their upper slope bottom trawl survey of southeastern Australia in 1996/97 with an earlier survey in 1976/77. Although natural variability cannot be ruled out, there was a consistent trend indicating that elasmobranchs had been fished down to a low level. The exception to this was the spiky dogshark (Squalus megalops), which showed an increase over the 20 year period. Some of the deeper-living dogsharks were virtually absent from some areas. It appears that the shark bycatch of the multi-species teleost trawl fishery and the growing importance of sharks for both meat and oil has severely depleted the shark stocks.
The discovery of large stocks of the teleost Pseudopentaceros wheeleri on North Pacific seamounts led to an intensive trawl fishery. Following a dramatic decline in catches, the fishery was closed, although surveys continued. The greatest bycatch in this fishery was the demersal shark Squalus mitsukurii. A detailed study on one seamount using longlines showed a decline in CPUE of more than 50% over two years. Further modeling suggested that the initial population had been reduced by 80% as a result of fishing. The decline in the population was not accompanied by a decline in mean length, perhaps indicating that there was little or no recruitment.
3.5 Vulnerability to exploitation
The biological characteristics of elasmobranch fishes apply equally well to the deep-water species and have been listed as follows by the ICES Study group on the Elasmobranch Fishes (Anon 1997a):
However, the Study Group also notes a number of other features that may increase the vulnerability of deep-water sharks to fishing impacts. The survival rate of discards and even escapees is either nil or low. Many species have a wide geographical range, probably involving long migrations. Life history stages can be separated, as for example in the squalid sharks, where for most species the juveniles are not found on the European continental slope. Because deep-water fisheries are comparatively recent, there has been a lack of monitoring or sampling of the stocks and hence a scarcity of biological and life history information. Methods of age estimation are unresolved and validation will be difficult.
The problems associated with obtaining catch statistics for sharks have been outlined by Compagno (1990). In assessing the relative importance of shark species to fisheries, Compagno placed the deep-water catsharks (Scyliorhinidae) and many small, deep-benthic and oceanic dogfish (Squalidae) in the category of minimal catch species.
The main problems associated with deep-water shark management can be summarised as follows.
With few exceptions, the landings of deep-water demersal sharks are of minor importance compared to the fisheries for coastal or oceanic pelagic sharks.
Most landings are a bycatch of other fisheries and the landings tend to be a mixture of several species.
The deep-water demersal sharks are less well known than the coastal sharks (eg Squalus acanthias) or the oceanic pelagics (e.g Prionace glauca) and are usually landed in grouped categories such as “sharks various”.
Often only parts of the shark, e.g. liver or fins, are retained.
Sharks of small adult size or the juveniles of marketable species are discarded. No records are kept of discards and there have been few scientific studies of discarding.
Sharks brought up from deep water in bottom trawls and subsequently discarded will suffer a high mortality.
Almost all sharks will take bait and therefore longlining is not a selective fishery and discarding rates can be high.
Little is known of the distribution, stock structure and migrations of the deep-water demersal sharks.
There are few age estimates of deep-water demersal sharks and none have been validated.
Little is known of the reproductive biology of the deep-water sharks. The squalid sharks, which are the most important in the fisheries, are ovoviviparous and the gestation period could be two to three years.
Because many of the fisheries where deep-water sharks are taken as a bycatch are in the process of developing, CPUE data are unreliable.
Many of the fisheries fall into the category of ‘highly migratory species and straddling stocks’, which is likely to result in uncontrolled fishing in international waters.
Bonfil (1994) commenting on the large bycatch of sharks, most of which are discarded, in the New Zealand deep-water orange roughy fishery stated the following. “The impact of this level of bycatch on the local stocks (of) sharks is unknown but it must be highly damaging and likely to lead to unsustainable exploitation. But this is difficult to verify as little information exists about the biology and population biology of these species. More research is needed on the levels of by catch, survival of discards and the deep sea shark populations themselves”. This statement is still pertinent and is equally appropriate to the ever increasing expansion of deep-water fishing.
The following people are acknowledged for contributing material to sections relating to their area of specialization: B. Seret, Muséum National d'Histoire Naturelle, Laboratoire d'Ichtyologie, France; G. Duhamel, Musée National d'Histoire Naturelle, Paris - Southern Ocean - CCAMLR area; J. Stevens, CSIRO, Australia and Southern Oceans; M. Francis, NIWA, New Zealand; José Miguel Casas, Instituto Español de Oceanografia, Cabo Estay - Canido, Spain
5. LITERATURE CITED
Allain, V. and B. Kergoat 1997. Biodiversitié et strategies démographiques des populations de poissons profond de l'Atlantique nord-est soumise à la pression de la pêche. Vie Mileau 47:285–294.
Anderson, E.D. 1990. Fishery models as applied to elasmobranch fisheries. In: Elasmobranchs as living resources: advances in biology, ecology, systematics, and the status of the fisheries. NOAA Technical Report NMFS 90: 473–484.
Anon 1995a. Report of the Study Group of Elasmobranch Fishes. ICES CM 1995/G:3, 88pp.
Anon 1995b. Report of the study group on the biology and assessment of deep-sea fisheries resources. ICES CM 1995/Assess:4, 91 pp.
Anon 1996a. Report of the Study Group of Elasmobranch Fishes. ICES CM 1996/G4, 49 pp.
Anon 1996b. Report of the study group on the biology and assessment of deep-sea fisheries resources. ICES CM 1996/Assess:8. 145 pp.
Anon 1997a. Report of the Study Group of Elasmobranch Fishes. ICES CM 1997/G:2, 123 pp.
Anon 1997b. Report of the ICES Advisory Committee on Fishery Management, 1996. Part 1. ICES Cooperative Research Report, No. 221: 318 pp.
Anon 1998a. Report of the Study Group of Elasmobranch Fishes. ICES CM 1998/G: 12, 29pp.
Anon 1998b. Report of the study group on the biology and assessment of deep-sea fisheries resources. ICES CM 1998/ACFM: 12, 172 pp.
Anon In press. Report of the ICES Advisory Committee on Fishery Management ICES Cooperative Research Report.
Baba, O., T. Taniuchi. and Y. Nose 1987. Depth distribution and food habits of three species of small squalid sharks off Choshi. Nippon Suisan Gakkaishi 53: 417–424.
Bakken. E., J. Lahn-Johannessen and J. Gjøsaeter 1975. Demersal fish on the continental slope off Norway. ICES CM 1975/ F:29. 15 pp.
Baliño, B.M., H. B. Boten, V. Fleming, A-M. Ruokangas and O.F. Tvedten 1993. Deep-benthos in the Nordic Seas. A seminar report. BFM 402. IFM Rappert, No. 17: 85 pp.
Bergstad, O.A. 1990. Ecology of the fishes of the Norwegian deep: distribution and species assemblages. Netherlands Journal of Sea Research 25: 237–266.
Bergstad, O.A., O. Bjelland and J.D.M. Gordon 1998. Fish Communities on the slope of the eastern Norwegian Sea. ICES CM 1998/0:30, 29pp.
Bigelow, H.B. and W.B. Schroeder 1948. Sharks. In: Fishes of the western North Atlantic, Memoir of the Sears Foundation for Marine Research, Volume 1, Part 1, Yale University, New Haven 1948: 59–546.
Bigelow, H.B. and W. B. Schroeder 1957. A study of the sharks of the suborder Squalidae. Bulletin of the Museum of Comapartive Zoology, Harvard University 117(1): 150 pp + Plates.
Blasdale, T. and A. W. Newton 1998. Estimates of discards from two deep-water fleets in the Rockall Trough ICES CM 1998/0:11, 17 pp.
Bonfil, R. 1994. Overview of world elasmobranch fisheries. FAO Fisheries Technical Paper, 341, Rome, FAO: 119 pp.
Bridger, J.P. 1978. New deep-water trawling grounds to the west of Britain. Laboratory Leaflet, MAFF Directorate of Fisheries Research, Lowestoft, No. 41: 40pp.
Charuau, A., H. Dupouy, and P. Lorance 1995. French exploitation of the deep-water fisheries of the North Atlantic. In: Hopper, A.G. (ed.) Deep-water Fisheries of the North Atlantic Oceanic Slope, Kluwer Academic Publishers, Netherlands: 337–356.
Clark, M.R. and K.J. King 1989. Deepwater fish resources off the North Island, New Zealand: results of a trawl survey, May 1985 to June 1986. New Zealand Fisheries Technical Report, No. 11: 56 pp.
Clark, M.R. and D.M. Tracey 1992. Trawl survey of orange roughy in southern New Zealand waters, June-July 1991. New Zealand Fisheries, Technical Report No. 32, 1992: 27 pp.
Clark, M.R. and D.M. Tracey 1994. Changes in a population of orange roughy, Hoplostethus atlanticus, with commercial exploitation on the Challenger Plateau, New Zealand. Fishery Bulletin US 92: 236–253.
Clarke, M. 1997. Deep-water trawl survey on the eastern slopes of the Rockall Trough. Fisheries Research Centre, Ireland, Demersal Survey Report 7, November 1997.
Clarke, M., P.L. Connolly and J.J. Bracken 1998b. Age estimation of the squaliform shark Centrophorus squamosus (Bonnaterre, 1788) using the second dorsal spine. ICES CM 1998/0:41.
Compagno, L.J.V. 1990. Shark exploitation and conservation. In: Elasmobranchs as living resources: advances in biology, ecology, systematics, and the status of the fisheries. NOAA Technical Report NMFS 90: 391–414.
Compagno, L.J.V., D.A. Ebert and P.D. Cowley 1991. Distribution of the offshore demersal cartilaginous fish (Class Chondrichthyes) off the west coast of Southern Africa, with notes on their systematics. South African. Journal of Marine Science 11: 43–139.
Connolly, P.L. 1997. Deep-water longline survey on the eastern slopes of the Rockall Trough. Fisheries Research Centre, Ireland, Demersal Survey Report 4, August 1997: 20 pp.
Connolly, P.L. and C.J. Kelly 1994. Sampling surveys for deep-water demersal fish in 1993. Fishery Leaflet, No. 163, Fisheries Research Centre, Ireland: 20 pp.
Connolly, P.L. and C.J. Kelly 1996. Catch and discards from experimental trawl and longline fishing in the deep water of the Rockall Trough. Journal of Fish Biology 49 (supplement A): 132–144.
Connolly, P.L. and C.J. Kelly 1997. Deep-water trawl and longline surveys in 1995. Fishery Leaflet, No. 173, Marine Institute, Ireland: 20 pp.
Correia, J., I. Figueiredo, M.J. Figueiredo and P. Machado 1997. Distribuição geografica e batimétrica de recursos de profundidade na região algarvia e suas variaçães sazonais em 1994. Parte II: Peixes cartilagíneos. Instituto de Investigaçãdas Pescas e do Mar.
Cox, G. and M. Francis 1997. Sharks and rays of New Zealand. Canterbury University Press, Christchurch, New Zealand: 68pp. Deprez, P.P., J.K. Volkman. and S.R. Davenport 1990. Squalene content and neutral lipid composition of livers from deep-sea sharks caught in Tasmanian waters. Australian Journal of Marine & Freshwater Research 41: 375–387.
Dupouy, H., V. Allain and B. Kergoat 1998. The discards of roundnose grenadier in the French fishery in ICES Subareas VI and VII. ICES CM 1998/0:20, 10pp.
Ehrich, S. 1983. On the occurrence of some fish species at the slopes of the Rockall Trough. Archiv für Fischereiwissenschaft 33: 105–150.
Erzini, K., J.M.S. Gonçalves, L. Bentes, P.G. Lino and J. Ribeiro 1998. The hake semi-pelagic (“pedro-boia”) longline fishery in Algarve (southern Portugal) waters: catch composition, catch rates, discards, hook selectivity, and interannual variability. ICES CM 1998/0:2, 12 pp.
Francis, M.P. 1998. New Zealand shark fisheries: development, size and management. Mar. Freshwater Res. 49(7): 579–592.
Golovan, G.A. 1978. Composition and distribution of the ichthyofauna of the continental slope of north-western Africa. Trudy Instituta Okeanologiya 111: 195–258.
Gordon, J.D.M. 1986. The fish populations of the Rockall Trough. Proceedings of the Royal Society of Edinburgh 88B: 191–204.
Gordon, J.D.M. and O.A. Bergstad 1992. Species composition Of demersal fish in the Rockall Trough, North-eastern Atlantic, as determined by different trawls. Journal of the Marine Biological Association of the United Kingdom 72: 213–230.
Gordon, J.D.M. and J. A. R. Duncan 1985. The ecology of the deep-sea benthic and benthopelagic fish on the slopes of the Rockall Trough, northeastern Atlantic. Progress in Oceanography 15: 37–69.
Gordon, J. D. M. and J. A. R.Duncan 1987. Deep-sea bottom living fishes at two repeat stations at 2200 and 2900 m in in Rockall Trough, northeasten Atlantic Ocean. Marine Biology 96: 309–325.
Gordon, J. D. M. and J. Mauchline 1990. Depth-related trends in the diet of a deep-sea bottom-living fish assemblage of the Rockall Trough. In: Barnes, M. and Gibson, R.N. (eds.), Trophic Relationships in the Marine Environment, Proc. 24th Europ. Mar. Biol. Symp., 1990: pp 439–452, Aberdeen University Press.
Gordon, J.D.M, N.R. Merrett, O.A. Bergstad and S.C. Swan 1996. A comparison of the deep-water demersal fish assemblages of the Rockall Trough and Porcupine Seabight, eastern North Atlantic: continental slope to rise. Journal of Fish Biology 49 (Supplement A): 217–238
Gordon, J.D.M. and S. C. Swan 1993. Biological parameters of deep-water fish species. Report to the Commission of the European Communities, DG XIV/C/1, 1992/10: 122 pp + appendices.
Gordon, J.D.M. and S.C. Swan 1997a. Final Report of EC DGXIV/C1 Contract 94/017 Deep-water demersal fishes: data for assessment and biological analysis.
Gordon, J.D.M. and S.C. Swan 1997b. The distribution and abundance of deep-water sharks on the continental slope to the west of the British Isles. ICES CM 1997/BB: 11.
Gubanov, E.P. 1993. Sharks of the Indian Ocean. Atlas-identification guide. (Akuly Indijskogo Okeana. Atlas-opredelitel). Moscow, VNIRO. 240 pp. (In Russian)
Graham, K.J., B.R. Wood and N.R. Andrew 1997. The 1996–97 survey of upper slope trawling grounds between Sydney and Gabo Island (and comparisons with the 1976–77 survey). FRV Kapala Cruise Report 117, Published by NSW Fisheries, Australia.
Haedrich, R.L., and N.R. Merrett 1988. Summary atlas of deep-living demersal fishes in the North Atlantic basin. Journal of Natural History 22: 1325–1362.
Haedrich, R.L, G.T., Rowe, and P.T. Polloni 1980. The megabenthic fauna in the deep sea south of New England. Marine Biology 57: 165–179.
Hansen, P. M. and F. Hermann 1953. Fisken og Havet ved Gr˜nland. Skrifter fra Danmarks Fiskeri og Havunders˜gelser 15: 128 pp.
Hareide, N.-R. 1991. Rapport Frå pr˜vefiske med M/S Stålodd ved Jan Mayen og aust-Grønland. Aug./Sept. 1991. M˜reforsking, ålesund, Unpublished manuscript.
Hareide. N. -R. 1992. For˜oksfiske med linefartoyet M/S Skarheim ved vest-Gr˜nland,Mai-Juni 1992. Moreforsking, ålesund, Unpublished manuscript.
Hareide, N.-R. and G. Garnes 1998. The distribution and abundance of deep water fish along the MidAtlantic Ridge from 43° N to 61° N. ICES CM 1998/0:39, 16pp.
Hareide, N.-R. and B. Thomson 1997. Felles Fiskebestander-nye ressurser Dypvannsfisk I Intenasjonalt Farvann. Rapport for Nordisk Atlantsamarbejde (NORA): 96 pp.
Hernandez-Perez, M., R.M. Rabanal Gallego, P.J.P. Alayon and A. B. Hernandez 1997. Squalene content in livers from deep-sea sharks caught in Canary Island waters. Marine and Freshwater Research 48: 573–576.
Holt, E.W.L and L.W. Byrne 1910. Fourth report on the species of the Irish Atlantic Slope. List of Recorded Species, with references. Fisheries Ireland, Scientific Investigations, 1908, V, : 7pp.
Hopper, A.G. (Editor) 1995. Deep-water fisheries of the North Atlantic slope. Kluwer Academic Publishers, Netherlands: 420 pp.
Hornung, H., M.D. Krom, Y.Cohen and M. Bernhard 1993. Trace metal content in deep-water sharks from the eastern Mediterranean. Marine Biology 115: 331–338.
Iglesias, S. and J. Paz 1995. Spanish North Atlantic deep-water fisheries. In: Hopper, A. G. (ed.) Deepwater Fisheries of the North Atlantic Oceanic Slope, Kluwer Academic Publishers, Netherlands: 287–295.
Jackson, P.A.B., M.H. Thurston and A.L. Rice 1991. Station data for the IOS Benthic Biological Survey of the Porcupine Seabight region (NE Atlantic) 1977–89. Institute of Oceanographic Sciences Report No. 281: 88 pp.
Jakobsdóttir, K.B. 1998. Maturity and other biological aspects of two deep water squaloid sharks, Centroscyllium fabricii (Reinhardt, 1825) and Etmopterus princeps Collett, 1904, in Icelandic waters. ICES CM 1998/0: 35, 24 pp.
Jónsson, G 1975. Skrá um íslenska fiska ásampt lýsingu á nokkrum peirra, Hafrannsóknir 7: 76 pp.
Jorgensen, O.A. 1995. A comparison of deep water trawl and long-line research fishing in the Davis Strait. In: Hopper, A.G.(ed.) Deep-water Fisheries of the North Atlantic Oceanic Slope, Kluwer Academic Publishers, Netherlands: 235–250.
Kelly, C.J., M. Clarke and P.L. Connolly 1997. Catch and discards from a deep-water trawl survey in 1996. Marine Institute, Ireland, Fishery Leaflet 175, Oct. 97.
Kelly, C.J., Connolly P.L. and M.W. Clarke 1998. The deep water fisheries of the Rockall trough; some insights gleaned from Irish survey data, ICES CM 1998/O:40, 22pp.
King, K. and M. Clarke 1987. Sharks of the upper continental slope - are they of value? Catch 14(4): 3–6.
Kock, K.H., G. Duhamel, and J.-C. Hureau 1985. Biology and status of exploited Antarctic fish stocks: a review. Biomass 6: 143 pp.
Last, J.R. and J.D. Stevens 1994. Sharks and Rays of Australia. CSIRO, Australia, 1994: 513 pp + 84 plates.
Lorance, P. and H. Dupouy 1998. C.P.U.E. Abundance indices of the main target species of the French deep-water fishery in ICES Sub-areas V, VI and VII. ICES CM 1998/O:19, 17 pp.
Magnússon, J. 1998. Deep water fisheries at Iceland. ICES CM 1998/O:66, 13pp.
Magnússon, J.V. and J. Magnússon 1995. The distribution, relative abundance, and biology ofd the deep-sea fishes of the Icelandic slope and Reykjanes Ridge. In: Hopper, A.G.(ed.) Deep-water Fisheries of the North Atlantic Oceanic Slope, Kluwer Academic Publishers, Netherlands: 161–199.
Markle, D.F. and J.A. Musick 1974. Benthic-slope fishes found at 900 m depth along a transect in the western N. Atlantic Ocean. Marine Biology 26:225–233.
Mauchline, J. (Editor) 1986. The Oceanography of the Rockall Channel. Proceedings of the Royal Society of Edinburgh 88B: 356 pp.
Mauchline, J. and J.D.M. Gordon 1983. Diets of the sharks and chimaeroids of the Rockall Trough, northeastern Atlantic Ocean. Marine Biology 75: 269–278.
Menezes, G., H.M. Silva, H. Krug, E. Balguerias, J. Delgado, J.G. Perez, I.L. Soldevilla, J.L. Nespereira, D. Carvalho and J.S. Morales 1997. Design optimisation and implementation of demersal cruise surveys in the Macaronesian Archipelagos. Final Report European Commission DG XIV/C/1 Study Contract 94/034: 162 pp + appendix.
Merrett, N.R. and P.A. Domanski 1985. Synopsis of catch and analysis data of deep-sea bottom-living fishes collected off the Moroccan slope, eastern North Atlantic (27 – 34) on Discovery cruise 77. Institute of Oceanographic Sciences, Report No. 208: 29pp.
Merrett, N.R., J.D.M. Gordon, M. Stehmann and R.L. Haedrich 1991a. Deep demersal fish assemblage structure in the Porcupine Sea Bight (eastern North Atlantic): slope sampling by three different trawls compared. Journal of the Marine Biological Association of the United Kingdom 71: 329–358.
Merrett, N.R., R.L Haedrich, J.D.M. Gordon and M. Stehmann 1991b. Deep demersal fish assemblage structure in the Porcupine Sea Bight (eastern North Atlantic): results of single warp trawling at lower slope to abyssal soundings. Journal of the Marine Biological Association of the United Kingdom 71: 359–373.
Moore, J.A. and J.K. Galbraith 1998. Results of exploratory fishing off the northeastern United States. ICES CM 1998/O:44, 9pp.
Moura, O., I. Figueiredo, P. Bordalo Machado and V. Henriques 1998. Research on deep-water species off the Portuguese continental coast. ICES CM 1998/O:67, 24 pp.
Muñoz-Chápuli, R. 1985. Análisis de la capturas de escualos demersales en el Atlántico NE (27 oN – 37 oN) y mar de Alborán (Mediterraneo occidental). Investigacion Pesquera 49: 121–136.
Murray, J. and J. Hjort 1912. The Depths of the Ocean. Macmillan and Co., London: 821 pp.
Nakaya, K. and M. Stehmann 1998. A new species of deep-water catshark, Apristurus aphyodes n. sp., from the Eastern North Atlantic (Chondrichthyes: Caracharhiniformes: Scyliorhinidae). Archive Fisheries and Marine Research 46: 77–90.
Newton, G. and N. Klaer 1991. Deep-sea demersal fisheries of the Great Australian Bight: a multivessel trawl survey. Bureau of Rural Resources Bulletin, No. 10, Australian Government Publishing Service, Canberra.
Nunes, A.A. 1994. Peixes a Madeira. Direcçäo Regional dos assuntos culturais, Funchal: 284pp + plates.
Olsen, H.E. 1995. Norwegian experience of deep-water fishing with longlines. In: Hopper, A.G. (ed.) Deep-water Fisheries of the North Atlantic Oceanic Slope, Kluwer Academic Publishers, Netherlands: 367–371.
Parin, N.V., K.N. Nesis, A.Yu. Sagaidachny and Yu.N. Shcherbachev 1993. Fauna of Walters Shoals, a seamount in the southwestern Indian Ocean. Trans. P.P. Shirshov Institute of Oceanology. Vol. 128: 199–216.
Petrakis, G. 1998. Catch per unit of effort fluctuations in deep waters in west coast of Greece (Ionian Sea). ICES CM 1998/O:50. 9pp.
Piãeiro, C. G., M. Casas and R. Bañón 1998. Current situation of the deep-water fisheries exploited by Spanish fleets in the north and northeast atlantic: a review. ICES CM 1998/O:10, 13 pp.
Pohle, G., T.J. Kenchington and R.G. Halliday 1992. Potentially exploitable deep-water resources off Atlantic Canada. Canadian Technical Report Fisheries and Aquatic Sciences, 1843: 85 pp.
Quero, J.C., J.C. Hureau, C. Karrer, C.A. Post and L. Saldanha 1990. Check-list of the fishes of the eastern tropical Atlantic. Volume 1, UNESCO, Portugal: 519 pp.
Ratz, H.-J. 1984. Qualitative and quantitative Untersuchungen der Ichthyozonose an der archibenthischen Zone des Rockall-Grabens and umliegender Banke (Westbritische Gewasser). Mitteilungen Institut für Seefischerei, Hamburg No. 34: 152 pp.
Reinert, J. 1995. Deep water resources in Faroese waters to the south, southwest and west of the Faroes - a preliminary account. In: Hopper, A.G.(ed.) Deep-water Fisheries of the North Atlantic Oceanic Slope, Kluwer Academic Publishers, Netherlands: 201–225.
Rice, A.L., D.S.M. Billett, M.H. Thurston and R.S. Lampitt 1991. The Institute of Oceanographic Sciences Biology Programme in the Porcupine Sea Bight: background and general introduction. Journal of the Marine Biological Association of the U.K. 71: 281–310.
Rose, D.A. 1996. An overview of world trade in sharks and other cartilaginous fishes. TRAFFIC International: 106 pp.
Santos, R.S. F.P. Porteiro, and J.P. Barreiros 1997. Marine Fishes of the Azores, Annotated checklist and bibliography, Arquipelago- Life and Marine Sciences (Supplement 1), Bulletin of the University of the Azores: 1–244.
Silva. H. M. 1983. Preliminary studies of the exploited stock of kitefin shark Scymnorhinus licha Bonnaterre, 1788) in the Azores. ICES CM 1983/G: 18, 13pp + 4figs.
Silva H.M. 1987. An assessment of the Azorean stock of kitefin shark, Dalatias licha (Bonn., 1788) ICES CM 1987/G: 66, 10pp.
Silva, H.M. and G.M. Menezes 1996. An intensive fishing experiment in the Azores. EC DG XIV/C/1 Study Contract 94/028: 62 pp.
Snelgrove, P.V.R. and R.L. Haedrich 1985. Structure of the demersal fish fauna off Newfoundland. Marine Ecology Progress Series 27: 99–107.
Stefanescu, C. 1991. Comunidades ictiologicas demersales del mar catalan (Mediterraneo Noroccidental) por debajo de los 1000 m de profundidad. Doctorate Thesis, University of Barcelona, Spain.
Stene, A. and A. Buner 1991. Fors˜ksfiske med liner vest for Shetland, Faer˜yene og Hebridene, samt på Reykjanesryggen. M˜reforsking, ålesund, Norway: 60pp.
Summers, G. 1987. Squalene - a potential shark product. Catch 14(9): pg 29.
Summers, G. and R. Wong 1992. Cosmetic products from semi-refined shark liver oil. INFOFISH International 2/92: 55–58.
Templeman, W. 1963. Distribution of sharks in the Canadian Atlantic (with special reference to Newfoundland waters). Bulletin of the Fisheries Research Board of Canada 140: 77 pp.
Ublein, F., F. Bordes, R. Castillo and A.G. Ramos 1998. Spatial distribution of shelf and slope dwelling fishes collected by bottom longline off Lanzarote and Fuerteventura, Canary Islands. P.S.Z.N: Marine Ecology 19: 53–66.
Viriato, A., M.J. Figueiredo, I. Figueiredo and J. Correia, J. 1997. Atlas de apoio à pesca de arrasto na vertente continental portuguesa. Instituto de Investigaçãdas Pescas e do Mar: 51pp.
Wilson, C.D. and M.P. Seki 1994. Biology and population characteristics of Squalus mitsukurii from a seamount in the central North Pacific Ocean. Fishery Bulletin, US 92: 851–864.
Whitehead, P.J.P., M.-L. Bauchot, J.-C. Hureau, J. Nielsen and E. Tortenese 1984. Fishes of the northeastern Atlantic and the Mediterranean. Volume 1, UNESCO, Paris: 510 pp.
Yano, K. and S. Tanaka 1984. Some biological aspects of the deep sea squaloid shark Centroscymnus from SurugaBay, Japan. Bulletin of the Japanese Society of Scientific Fisheries 50: 249–256.
Yano, K. and S. Tanaka 1988. Size at maturity, reproductive cycle, fecundity, and depth segregation of the deep sea squaloid sharks, Centroscymnus owstoni and C. coelolepis in Suruga Bay, Japan Nippon Suisan Gakkaishi 54: 167–174.
Yatsu, A. and O. J˜genson 1988. Groundfish biomass estimates from a stratified-random bottom trawl survey off East Greenland in 1987. ICES CM 1988/G:61.