Some of the most important shark fisheries in the North Atlantic have been carried out by Norwegian vessels. These fisheries have varied since the end of World War II with an increasing trend up to 1963, followed by a general decrease to levels around 7500t/yr since 1981 (Figure 2.2). Catches rose in the last three reported years. Elasmobranchs are not important for Norway judging from recent trends which show that elasmobranchs represented only 0.44% of the total fisheries production of Norway. Moreover, Norwegian shark and ray fisheries contribute only 1.21% to the world elasmobranch production during 1987–1991 (Table 2.2).
Catches of piked dogfish Squalus acanthias, have commonly accounted for the largest part of the total elasmobranch catches. Nevertheless, important fisheries for porbeagles existed in the 60's and for basking sharks during the last decade. While marketing and economical constraints have traditionally inhibited basking shark fisheries (Maxwell 1952; O'Connor 1953; Kunslik 1988), apparently the porbeagle, (Lamna nasus), fishery declined, at least in part, as a result of over-exploitation (Gauld 1989, Myklevoll 1989a, Anderson 1990).
Figure 2.8. Elasmobranch catches of Argentina, by species, by species groups, during 1977-1991 (Data from FAO).
Figure 2.9. Elasmobranch catches of Norway, by species groups, during 1977-1991 (Data from FAO).
Norwegian elasmobranch fisheries are recovering after a prolonged decline. For the first time in almost 20 years, catch trends are increasing. FAO data for 1978-1991 (Figure 2.9) show catches of piked dogfish declining from more than 12 000t in 1978 to 2986t in 1986 then rising to 9627t in 1991, averaging 5715t/yr (53% of elasmobranch catches for this period). Catches of basking sharks, (Cetorhinus maximus) show a pattern similar to that of piked dogfish although their recovery is more modest. Basking shark catches fell from 11 335t in 1979 to only 352t in 1987, but were 1932t in 1990 and averaged 3929t/yr (36%) during this period. Catches of rays are fairly stable around 1115t/yr (10%). Small quantities of probeagles are still caught on average 67t/yr.
Although the published data from the directed Norwegian fishery of the 60's is not considered (Gauld 1989; Anderson 1990), it is clear that this fishery caught large amounts of porbeagles. The summary of this fishery given here is based on Aasen (1963) and Myklevoll (1989a). Operations started as a coastal activity and after 1930 expanded from Norwegian waters northwest to the Orkney - Shetland area and the Faroes, then south into Irish waters and finally went to Canada and northern USA. Distant water operations by specialised freezer vessels 43-50m long deployed longlines with up to 5000 hooks in waters 10 - 30 m deep. Sharks less than 10kg were discarded as no market for them existed. The home fleet consisted of wooden boats 23-30m long which kept the catch on ice. Once the NW Atlantic porbeagle stocks declined to unprofitable levels by 1965, the fleet switched to mako sharks off North West Africa. Dressed carcasses of porbeagles were exported frozen to Italy while fins were marketed in the Far East. At present, only by catches of porbeagles from purse - seining, trawling and gillnet fisheries are landed. Norwegians do not even take their 200t TAC in EC waters.
The basking shark fishery started in the 16th century when the dried flesh was used as food (Kunzlik 1988 and Myklevoll 1989b), and has been an important tradition directed fishery. The major expansion of the fishery started in 1960, stimulated by demand for liver oil. Small wooden vessels 15-25m long, using harpoons operated mainly during April-August. Experiments to use the flesh of basking sharks (for fishmeal) and their hides failed. Consequently, in practice comparable to “finning”, Norwegian fisherman took just the liver for oil extraction and discarded the carcasses. Later, they also took the fins for export to the Orient. During 1959 - 1980, catches ranged between 1266 and 4266 sharks per year, but have since declined. EEC agreements with Norway were limited their catches to 400 / yr of livers since 1978. This corresponds to 2 400t / yr whole weight, taking livers as 1/6 of whole weight. Socio-economic constraints which include limited markets and an ageing fleet coupled with erratic distribution of the sharks, are the reasons for the decline of this fishery and this fishery for basking sharks has not taken even the TAC in EEC waters. The oil from the livers is sold for extraction of squalene, a hydrocarbon used in cosmetics and aviation but richer sources have since been found in deep - sea sharks of the genus Centrophorus and the market for basking sharks is shrinking. In general, the dynamics of Norwegian elasmobranch fisheries seem to be strongly influenced by economic and social factors (Myklevoll 1989a, 1989b, 1989c). Many of these fisheries in Norway have declined or collapsed for reasons independent of the resource size.
Much about the Norwegian fishery for piked dogfish Squalus acanthias in the northeast Atlantic is summarized by Holden (1977) and Myklevoll (1989d). This fishery dates from 1931. Subsequent expansion of the markets led to Norwegian catches of 8767t by 1937 peaking at almost 34 000t in 1963. Since then catches have slowly fallen to less than 6 000t in the 80's. During 1950 - 1970, Norwegian longliners fished mainly in their coastal waters during winter and in Scottish waters during summer and autumn. The fishery exported most of the catch which was used in fish and chips shops in England. Until the early 70's, this fishery constrained the expansion of the British fishery, due to the larger sizes, better appearance and lower price. In recent years, large numbers of piked dogfish migrated into unusually northern parts of Norway enabling a fishery. This might account for the increase in catches during 1989 - 91.
During the first half of this century, Norway had a fishery for greenland sharks, (Somniosus microcephalus), both as a specialized activity and in combination with sealing. Judging from the data reported by Myklevoll (1989c) this fishery peaked in 1917 when 17 049 hectolitres of livers were landed. Probably because of failling market prices, the fishery ceased in 1960. Skates and rays have never been exploited a targeted fishery in Norway and all catches are incidental to piked dogfish, ling, halibut and trawl fisheries (Myklevoll 1989e). Species of no commercial value and small specimens are commonly discarded.
Despite developing several specific shark fisheries, Norwegian interest in elasmobranch research have been relatively poor. Of the three most important shark fisheries of Norway (piked dogfish, porbeagle and basking sharks), only the piked dogfish has been studied in any depth in a research programme from 1958 to 1980. This produced the first known assessment of an elasmobranch fishery (Aasen 1964). Aasen estimated a maximum equilibrium yield of 50 000t/yr for what he considered a single stock of piked dogfish for Northern and Western Europe. By 1961, this yield was already surpassed. Porbeagles were briefly studied while the fishery was expanding and this produced one of the first attempts to estimate growth in sharks from vertebral rings (Aasen 1963). There has been only limited research done on basking sharks.
Norwegian vessels fish orange roughly off Australia and New Zealand, but no details about these activities could be found. The use the, probably large, by catches of deep sea sharks from this fishery is unknown (see Section 2.3.4).
The elasmobranch fisheries of the ex-USSR were important. Former USSR fisheries for elasmobranchs were not recorded separately from the rest of their fish catches in FAO yearbooks before 1964. Since records began, catches have soared, reaching 59 000t in 1975, declining equally precipitously to about 20 000t in 1977. Since then, catch levels have varied between 10 000-20 000t /yr (Figure 2.2). With the breakup of the Soviet Union, catches plummeted in 1990-1991. Elasmobranchs contributed 0.11% of the total catches for 1987-1991, the lowest among major elasmobranch fishing countries. The contribution to world elasmobranch fisheries by this country was 1.75% in the same period. As for most former USSR fisheries, the elasmobranch catches came from catches of its enormous globalfishing activities and a great variety of species are reported under two main headings: rays and various elasmobranchs. The changing characteristics of former USSR fisheries, which largely depended on agreements with various nations, makes their analysis difficult.
Data from FAO (Figure 2.10) show that from 1978 to 1991, rays accounted for 66% (8761t / yr) of the total former USSR elasmobranch catches. Various elasmobranchs represented 31% (4109t / yr) of the catch. Catches of Squalus acanthias accounted for the remaining 3% (327t / yr) of the total. Most of elasmobranch catches of the former USSR probably were taken by large trawlers which is shown by their large catches of batoids. Rays were taken mainly in FAO areas 21 (37%), 47 (26%), 27 (15%) and 37 (10%) with the remaining (12%) taken in areas 34, 41, 51 and 71. Catches of various elasmobranchs came chiefly from areas 37 (37%), 47 (31%) and 34 (25%), with the rest (7%) taken in areas 27, 51, 71 and 81. Catches of these two groups in Area 37 consist of thornback ray Raja clavata and picked dogfish Squalus acanthias fisheries in the Black Sea.
Ivanov and Beverton (1985) indicate that specialized fisheries for these two species are carried out by Crimean and Caucasian fishermen in the Black Sea. Thornback rays are fished with baited longline and caught in bottom gillnets set for piked dogfish. Piked dogfish are also taken by trawl off the northwester coast and by bottom longlines and fixed nets along the coasts of Crimea and Caucasia. After the continuous decline of elasmobranch catches by former USSR fisheries until 1982, catches (mainly of batoid fishes) slowly increased until political events practically shut down all fisheries.
The United Kingdom has one of the most stable elasmobranch fisheries in the world. There has been a steady decrease from 30 000t / yr in the early post-war years to the current level of about 22 000t/yr (Figure 2.2). During 1978 - 1991, catches varied between 20 000t and 25 000t and are correlated to changes in the catches of piked dogfish Squalus acanthias which averaged 63% (13 820t/yr) of total elasmobranch catches (Figure 2.11). Almost 47% percent of piked dogfish catches this period were caught in England and Wales, with an equal amount caught in Scottish waters. The remaining 6% came from Northern Ireland. Catches of rays averaged 36% (7877t/yr) of all elasmobranchs and have remained fairly constant with a slight tendency to increase. Approximately 49% of ray catches are taken in Scotland and the same amount in England - Wales, while Northern Ireland contributes about 2%. Less than 1% of the total elasmobranch catch of the UK is made up of Scyliorhinids, Squaloids and unspecified elasmobranchs. As a group, chondrichthyans are relatively important to UK fisheries comprising 2.63% of the total catches during 1987 - 1991.
Holden (1977) summarizes the information for the piked dogfish (Squalus acanthias) fishery, which has been fished by England since the begining of the century but catches did not exceed 2850t until 1931. Scottish catches appeared in records in 1954 and combined catches in UK remained between 6000 - 10 000t / yr during the 60's and peaked at 19 400t in 1978. During 1950-1970 the amount of spinydogfish caught was dictated by local market demand, and was taken as by catch by trawlers targeting cod, haddock and hake.
According to Kunzlik (1988), fisheries for basking sharks (Cetorhinus maximus) existed in the UK during the 40's mainly on the west coast of Scotland. Most were short lived because of marketing difficulties (Maxwell 1952). Basking sharks were hunted mostly during the summer with hand or whaling harpoons from vessels adapted from other fisheries but catches never surpassed 300 sharks per year (approximately 600t/yr). As for Norwegian and other basking shark fisheries in the world, they mainly took livers and present catches are minimal. Since 1983, only one boat fishes, opportunistically, for basking sharks in Scotland.
Porbeagle sharks have been sporadically landed in small quantities (less than 30t/yr), mainly on an incidental basis. The exception was in 1987 - 1988 when porbeagles were unusually abundant for a couple of months in the Shetland Islands and 35 - 45t were taken in four months (Gauld 1989).
Although UK catches of skates and rays are larger in the North Sea, most of the available information comes from the Irish Sea. British fisheries for skates and rays in the Irish Sea consist mainly of Raja montagui, R. clavata, R. brachyura and R. naevus (Holden 1977), in respective order of importance. Fishing pressure has apparently caused a decline in some local stocks. Brander (1977-91) believes that skates and rays of the Irish sea are in need of immediate management measures to allow stock to recovery and attributes the disappearance of Raja batis from the Irish sea to excessive commercial fishing. According to data summarized in Ryland and Ajayi (1984), stocks of rays in the Bristol Channel, which used to provide 27% of the UK ray catch, were halved during 1964–1974. For the North Sea, Vinther and Sparholt (1988) estimate the biomass of R. radiata, and all other rays during the mid 80's, as 160 000-252 000t and 294 000–464 000t respectively. Data presented by these authors suggest declines in the abundance of R. batis, R. clavata, R. naevus and increases in abundance of R. radiata. A later biomass estimate of R. radiata is 100 000t (Sparholt and Vinther 1991).
Figure 2.10. Elasmobranch catches of USSR, by species groups, during 1977-91 (Data from FAO).
Figure 2.11. Elasmobranch catches of U.K., by species groups, during 1977-1991 (Data from FAO).
Research on elasmobranchs is comparatively active in Britain; however, management seems to be neglected. A fair amount of research was done on piked dogfish (Holden 1968, Holden and Meadows 1962, 1964) but despite the general guidelines proposed by Holden based on his assessment of the fishery, no regulation measures were taken. Also, despite the availability of a reasonable number of basic studies on rays, no management specifically directed to these fishes appears to exist. This might be due, at least partially, to the complications of setting management regulations for multispecific fisheries, especially bottom - trawl fisheries.
Elasmobranch fisheries of the Irish Republic have been of minor importance until recently, when catches exceeded 10 000t / yr (Figure 2.2). In the period 1987 - 1991 they contributed 1.03% to the world catch. Despite this small amount, elasmobranch catches are relatively important for Ireland, representing 3.03% of the total landings. This is rather high compared to other major elasmobranch - fishing countries (Table 2.2).
Rays have been long exploited in Ireland in small quantities. Piked dogfish Squalus acanthias is the other main elasmobranch resource and has gained much attention since the beginning of the 80's. Since 1983, piked dogfish catches have comprised the major proportion of the total elasmobranch catch (Figure 2.12). During 1978 - 1991 rays and dogfish were equally represented with catches of 3048t/yr and 3067t/yr respectively. While the catches of rays have remained practically constant since 1978, those for dogfish increased tremendously in less than five years, suffered a small fall in 1986 and recovered and fell again in 3 years. Recent statistics suggest a relative stability has been achieved in this fishery. Fahy (1989a,b, 1991) and Fahy and Gleeson (1990) cover most of what is known about recent elasmobranch fisheries of Ireland and most of the following is taken from them.
Recordings of rays landings of goes back to 1903. No more than 600t/yr was recorded before 1940 when catches began to rise partially due to increased consumption in Ireland, up to the late 70's when they sharply increased, reaching 3 000t in 1985. Rays have traditionally been taken in greatest quantities (around 50% of the total) from the east coast. Since 1975, about 25% has been taken from the north coast and the rest from the south and west coasts. Most of the landings are not sorted by species but are defined by a casual process by similarities in size and appearance. At least 18 trawling vessels catch rays from eastern Irish ports. Thirteen otter trawlers and four beam trawlers operate from the southeast, but more vessels are believed to participate in the fishery. Although most of these vessels catch rays incidentally to prawns and other bottom fish, a small ray fishery appears to occur on a seasonal basis. At least nine species of rays are found in the catches but sampling of the commercial landings indicates that Raja brachyura, R. clavata, R. naevus and R. montagui are the most common in order of importance. R. microocellata, R. batis, R. fullonica, R. undulata and R. alba are sporadically caught. The catch consists mostly of small (less than 60 cm TL) and medium sized rays (between 60–70 cm TL) which account for 60–80% of the weight. Most species are totally recruited to the fishery after 2 years of age but R. naevus enters at age 3. At least 50% of the catches of R. clavata and R. brachyura in the east coast are made of 0-2 age class fish. Total mortality estimates for the most important species range from 0.54-0.74 and although the populations are heavily exploited, particularly in the southeast fishery, they continue to produce good yields.
Figure 2.12. Elasmobranch catches of Ireland, by species groups, during 1977-1991 (Data from FAO).
Fisheries for dogfish occur around Ireland country but are more concentrated on the west coast. Catches were high in the north (Co. Donegal) during 1982-1985 but landings in the south (Co. Kerry) increased during 1986–1987 as a result of effort being shifted to the south due to decreasing catches in the north. Dogfish were considered a nuisance but now a fishery is specifically directed at them. On the west coast, otter trawlers fish mainly male dogfish in waters sometimes exceeding 100 m while monofilament gillnets of 6.4cm mesh size are used in shallow waters where they catch high proportions of pregnant females. Piked dogfish in the west of Ireland are fully recruited to the fishery at around 17 years of age and total mortality coefficients have been estimated at 0.24 for females and 0.30 and for males. Fahy and Gleeson (1990) report that monthly CPUE of gillnetters in Carrigaholt plummeted by 80-90% over a two-year period. Available information is insufficient to definitively conclude about the causes of stocks depletion but it seems that they are close to being overfished. Total female spawning biomass for Carrigaholt was estimated at 5700t by Fahy and Gleeson. Most of the catches are destined for export but there is no apparent reason for the boom in this fishery.
A fishery for basking sharks began in 1947 at Keem Bay on the west coast of Ireland (Kunzlik 1988). Initially harpoons and nets were used but by 1951 only encircling nets or entangling nets, set perpendicular to the shore and made of sisal with mesh sizes of 33cm, were used. Initially, the liver was only taken but in later years fins and meat were also used. In 1973 harpoons were reintroduced to this fishery and another harpoon fishery started in the south east coast of Ireland. The west coast fishery peaked (around 1500 sharks annually) during the early 50's and declined after 1955, probably as a response to the shrinking market for livers. Catches remained below 100 sharks/yr during most of the period 1963-1973 and increased to almost 400 sharks in 1975 when the last records are available. Some trials to develop a commercial blue shark fishery with longlines off the south coast of Ireland were done in 1990 (Crummey et al. 1991). Whether a fishery will develop is, as yet, unknown.
French elasmobranch fisheries are another relatively stable fishery. Two periods of more or less sustained catches exist. From 1948 to 1960, catches oscillated around 15 000t / yr then in 1961 jumped to a higher more variable level around 35 000t/yr (Figure 2.2). During 1987-1991, elasmobranchs represented 3.78% of the total fishery production of France, the highest among European countries and rather high globally. French catches are 4.79% of world elasmobranch production.
Between 1978 and 1991, French catches of skates and “various dogfishes” were stable. Piked dogfish, “various elasmobranchs” and porbeagles showed a slight declining trend (Figure 2.13). During this period, skates averaged 42% (14 499t / yr) of the total elasmobranch catches while piked dogfish, various dogfishes, various elasmobranchs and porbeagles averaged 32% (10 806t / yr), 18% (6139t / yr), 6% (2103t / yr) and 2% (531t / yr), respectively. Piked dogfish and skates are caught by French vessels mainly in the Northeast Atlantic but small catches of skates are also taken in the northwest Atlantic and the Mediterranean Sea. According to Gauld (1989), a small flotilla of French vessels based in Britain specifically target porbeagles with longlines in the Bay of Biscay and in Irish waters taking about 75 % of the total French porbeagle catch. The remainder is landed as by catch of trawl and seine fisheries.
Figure 2.13. Elasmobranch catches of France, by species groups, during 1977-1991 (Data from FAO).
Tetard (1989a, 1989b) summarizes information about shark and batoid fisheries for France and separates catch statistics into species or species groups. The following is from his account. The catch of batoids of France consists of at least 8 species of skates and rays. Separation of ray species is possible as each species attains a different price. Raja naevus and R. clavata are the most important accounting for about 25% and 17% respectively of batoid landings during 1978-1987. Raja montagui and a group formed by R.batis and R. oxyrinchus comprise 4% and 3% of the catch respectively. Dasyatis pastinaca, Myliobatis aquila and Raja fullonica are of minor importance and compose only 1% of the catches. Unidentified rays comprise the remaining 50%. Most of the French catches of rays are taken in waters around the Celtic Sea and the English Channel and to some extent in the Irish sea and the North of the Bay of Biscay. Rays are mostly caught by bottom trawling. Raja clavata is actively sought for its highly desired meat. Tetard highlights the almost complete disappearence of R. alba from the catches and the apparently declining catches of R. clavata. though yields of R. naevus seem to be increasing. He also notes that an incited study indicates that the yield per recruit of R. naevus is at an optimal value. Judging from Tetards, it appears that no management regulations exist for any of these species in French waters.
Shark landings are chiefly composed of piked dogfish and catsharks. The latter are mainly Scyliorhinus canicula with a minor amount of S. stelaris. Catshark catches occur as by catch in trawler and longline fisheries and comprise about 32% of the shark catch. The piked dogfish fishery is one of the few directed fisheries for sharks in France accounting for almost 57% of all shark landings. During 1987, approximately 27 longliners 8–25m long (three of them automatic longliners) were targeting piked dogfish. Although, about 80% of the landings came from bottom trawlers. The main fishing grounds for piked dogfish are the Celtic Sea and, formerly, Northern Irish waters, and the North Sea. Tope, (Galeorhinus galeus), ranks third in importance among shark catches, with about 6% of the total, but catches are declining. The fishery for porbeagles is also a directed fishery representing about 3% of the shark catch. Some shortfin mako shortfin mako sharks are caught incidentally in the longlines of this fishery. About 75% of the landings come from longliners and the rest from trawlers. The main fishing grounds are offshore waters, from Spain to Ireland in winter, and closer in shore and around the Channel Islands in spring. Smoothhounds, Mustelus mustelus and M. asterias comprise about 1% of the shark catch. Some minor quantities of blue shark and angel shark, (Squatina squatina), are landed incidentally by longline and trawl fisheries respectively.
France is both the major producer and importer of shark in Europe. High exports of mainly porbeagle and tope shark to Italy results in a deficit of supply and imports have increased since 1982 (9000t in 1986). However, some problems related to mercury content of shark meat seem to limited French exports to Italy, and consequently the effort directed towards porbeagle sharks. The home market is also increasing. There is strong domestic demand for Lamna nasus, Squalus acanthias and Galeorhinus galeus as “saumonette” in schools and restaurents. The domestic demand for Squalus acanthias is not met by French landings and considerable quantities are imported from the United Kingdom.
Spanish elasmobranch catches were steady during 1947–1971 when yields varied from 10 000–15 000t / yr. This was followed by a collapse in the early 70's and a subsequent recovery in the 80's to 15 000–20 000t/yr (Figure 2.2). Elasmobranchs comprise 1.3% of the total fishery production of Spain and contribute 1.2% of the world catch (Table 2.2).
Disaggregated data for the years 1978–1991 indicate that the major source of recent increased catches comes from the skate fisheries which have grown consistently since 1980 (Figure 2.14). The bulk of skates comes from the Northwest Atlantic (an average, 80% of skate catches for the period) and the rest from the northeastern Atlantic. No information on the species composition is available. Catches of unspecified sharks have also increased in a similar way but these are taken mainly in the Northeast Atlantic. These include shortfin makos (Isurus oxyrinchus), porbeagles (Lamna nasus), small-spotted catshark (Scyliorhinus canicula) and some squaloids. Various species of rays are fished in small quantities mainly in the Mediterranean Sea along with unspecified elasmobranchs which are also caught in the central eastern Atlantic (FAO Area 37). Skates comprise 63% (7125t/yr) and unspecified sharks 21% (2259t/yr) of elasmobranch catches, the contribution of “various elasmobranchs” was 11% (1168t/yr).
All elasmobranch landings in Spain come from incidental catches of trawl or longline fisheries (R. Muñoz-Chápuli, pers. comm., 1992). Muñoz-Chápuli (1985a) reports on the landings of Spanish commercial bottom trawlers operating in depths up to 500m. Scyliorhinus canicula dominate landings from the mouth of the Mediterranean, southern Spain and northwest Africa. Centrophorus granulosus and Squalus blainvillei are also landed from these areas. In the entrance of the Mediterranean, Galeus melastromus is also important while another 11 species are caught in smaller amounts in both regions (Table 2.6).
|Hexanchus griseus||Lamna nasus|
|Heptranchias perlo||Isurus oxyrinchus|
|Deania calcea||C. falciformis|
|Galeus melastomus||C. signatus|
|Mustelus mustelus||Prionace glauca|
|M. asterias||Galeorhinus galeus|
Muñoz-Chápuli (1985b) reports that landings from longline vessels fishing from the Azores to the Cape Verde Islands, are dominated by Prionace glauca, Isurus oxyrinchus and Sphyrna zygaena while another 13 other species are of minor importance (Table 2.6). Both reports likely reflect the abundance of the species in such areas and the species retained on board. Spanish swordfish longliners caught 304t of shortfin makos and 20t of porbeagles from the north and central east Atlantic during 1984 (Mejuto 1985). Makos were more abundant during September-December and catches were mainly composed of sharks 100–240 cm fork length. Males were more than twice as frequent in the catch as females. Porbeagle catches were more abundant in March, September and October. Individuals were mostly 150–225cm fork length.
Figure 2.14. Elasmobranch catches of Spain, by species groups, during 1977-1991 (Data from FAO).
The level of historical imports of sharks from Norway (porbeagles), France (porbeagles and tope) and Argentina (smooth-hounds), show elasmobranchs are well appreciated in Italy. Nonetheless, sharks and rays have long been of minor importance in Italian fisheries. Catches did not exceed 6000t / yr until the mid 80's when more than 10 000t / yr were taken (Figure 2.2). Currently, elasmobranchs represent only 1.89% of the total catches in Italy and the Italian catch of sharks and rays comprises only 1.51% of the world elasmobranch catch (Table 2.2).
During 1978-1991, smooth-hounds, (Mustelus spp.), averaged 52% (4463t/yr) of elasmobranch catches and rays, 38% (3340t/yr). “Various elasmobranchs” contributed 10% (860t / yr). Catches of all groups grew during the expansion of the fishery which peaked in 1985 (Figure 2.15). Smooth-hounds were all taken from Mediterranean waters along with 91% of the ray catch. The rest were caught in FAO Areas 34, 47, 48, 51 and 21. Catches of “various elasmobranchs” were taken in FAO Area 34 (70%) and Areas 47 (7%), 51 (16%) and 41 (7%). Small catches of blue sharks, (Prionace glauca), are landed as a bycatch of the drift longline swordfish and albacore fisheries of the Gulf of Taranto, where averages of 14.5t / yr and 4t / yr respectively were landed during 1978-1981 (De Metrio et al. 1984). During this period, an average of 12 boats fished for swordfish from April to August using 700 to 1000 (Mustad no. 1) hooks per boat. On average, 44 boats fished for albacore during August to December using 2000 3cm hooks per boat. Due to the different hook size, and probably seasonal cycles of the species, the swordfish boats caught blue sharks of 25kg average weight whereas blue sharks from the albacore boats averaged 3kg. De Metrio el al. report that the meat of Prionace glauca is fraudulently sold in Italy as Mustelus. It is therefore likely that the blue shark catch is probably reported under Mustelus spp. in official statistics.
Figure 2.15. Elasmobranch catches of Italy, by species groups, during 1977-1991 (Data from FAO).
Information about elasmobranch fisheries in this region is scarce. Most of the major elasmobranch - fishing countries give little detail of the catch composition and reports are limited and difficult to obtain.
Nigeria is the only African country with a major elasmobranch fisheries. FAO statistics for Nigeria are poor and have only appeared regularly since 1970. They show a fairly unstable fishery with an overall trend of decreasing catches from more than 30 000t / yr in the early 70's to less than 10 000t since 1986 (Figure 2.2). Without background information it is difficult to interpret these figures. Despite the fall in yields, elasmobranchs continue to be a relatively important resource for Nigeria contributing 2.92% of the total fishery production during 1987-1991. The catch of sharks and rays of Nigeria contributes 1.91% of the world total. FAO data from 1977–1991 show that most of the catches are not recorded by species. A group of “various elasmobranchs” accounts for 89% (15 827t/yr) of the catches while Squalidae and a group of skates and rays accounts for less than 1% (7.6t/yr) and about 10% (1703t/yr) respectively (Figure 2.16).
Elasmobranch fisheries of Pakistan were of prime importance on a global scale until recently when production plummeted. Elasmobranch landings grew almost exponentially from the late 40's to a peak of about 75 000t in 1973, dropped about 50% during the following three years and then recovering to peak levels for another 6 years. Catches collapsed in 1983 but have recovered during the last 10 years to the present levels of about 45 000t (Figure 2.2). Given the lack of information on Pakistani fisheries it is difficult to determine the reasons for these changes in catches. The relative importance of elasmobranchs in Pakistan is among the highest in the world, 7.42% of the total national catches during 1987–1991. This level must have been at least double during the bonanza of the late 70's. Pakistan landings comprise 4.99% of the world elasmobranch production (Table 2.2).
Batoids and grey sharks (Carcharhinidae) constitute most of the catches, averaging 54% (24 380t/yr) and 45% (20 200t/yr) of the elasmobranch production respectively during 1977-1991. Since 1987, catches of sawfishes (Pristidae) and guitarfishes (Rhinobatidae) have been reported separately, but they account for <1% and 1% of the elasmobranch catches respectively (Figure 2.17). While grey shark catches declined steadily during the late 70's and early 80's batoid catches dropped abruptly by 43 000t in one year (1983) causing the overall collapse. Grey sharks have since been the major species in the elasmobranch catches.
Detailed information about Pakistani elasmobranch fisheries is poor and a report from the Indo-Pacific Tuna Development and Management Programme (IPTP 1991) is almost the only source of information. According to this document, Karachi is the only landing site for the mechanized gillnet fleet in Sind province. Sharks are caught mainly by pelagic gillnet boats fishing as far as Somalia, the Yemen and Oman although small quantities are also landed by bottom gillnetters working in coastal areas of Pakistan. There were 394 mechanized gillnetters in Pakistan in 1989, 185 in Sind province and 209 in Baluchistan. The vessels based in Karachi range in length from 20 to 25m and 5 to 7m in breath and use diesel engines of 88–135 HP. These fisheries are important socio-economically employing considerable numbers of fishermen. Small boats carry 15–17 crew on trips of about 10 days; larger boats carry up to 25 fishermen for 20–30 days and occassionally 60 days. Catches are usually salt dried on larger vessels and kept on ice in the smaller ones. Gillnets are hand-woven out of multifilament polyamide twine and are 80 meshes deep and 2.5–9km long (average of 5.2km). Mesh sizes are 10–16cm and mainlines of 14–16mm diameter. Sharks are categorized into 8 types depending on size and species. Effort in this fishery increased from 23 000 fishing days in 1988 to 28 000 in 1989 then fell to 26 000 days in 1990. About 93% of the shark catch comes from pelagic driftnet vessels. The production of sharks of this driftnet fleet was about 3860t/yr during 1988–1990. Shark production during this period was correlated with distance to fishing grounds. The greatest catches came from Somalian waters, the most distant fishery. Shark yields decreased by 44% from 1989 to 1990 while other catches fell 32% during the same period. Some efforts to introduce longline fishing for sharks, rays and other species in Pakistan are described by Prado and Drew (1991). Apparently gillnets are more favoured in Pakistan because of their higher catch rates of valuable species.
Figure 2.16. Elasmobranch catches of Nigeria, by species groups, during 1977-1991 (Data from FAO).
Figure 2.17. Elasmobranch catches of Pakistans, by species groups, during 1977-1991 (Data from FAO).
There have traditionally been important fisheries for elasmobranchs in India with a relatively steady growth up to the mid 70's, followed by a period of stability during most of the 80's, then a tremendous increase in catches in 1987 resulting in India becoming one of the top three elasmobranch producers in the last ten years (Figure 2.2). Indian production of sharks and rays represents 8.78% of the world elasmobranch catches! Still, because of large inland yields, elasmobranchs comprise only 1.72% of total national catches in 1987–1991. Catches results are not given by species or families in the statistics and the composition of catches is only known by FAO areas. Approximately equal amounts (about 26 000t/yr) were obtained from both FAO areas for the period 1977–1991. Catches from the west coast were slightly larger than those of the east coast during 1977–1991 (Figure 2.18). There is a relatively large number of articles on elasmobranchs' exploitation and utilization in India, especially for the 80's.
Figure 2.18. Elasmobranch catches of India, by species groups, during 1977-1991 (Data from FAO).
During 1983–1985 sharks comprised 55% of the elasmobranch catch of the country (Appukuttan and Nair, 1988). The main fishing areas in order of importance were Gujarat, Maharashtra, Kerala andhra Pradesh, Karnataka and Tamil Nadu and important fishing grounds for sharks are reported for Ashikode, Kerala Province (Anon. 1983). Sharks catches are incidental to other fisheries in India (Appukuttan and Nair 1988) and are mainly taken with longlines, which vary in design by region, and are also as by catch of trawlers using disco nets off Ratnagiri (Maharashtra), with bottom set gillnets in Porto Novo (Tamil Nadu) and by shrimp trawlers of Kerala (Devaraj and Smita 1988; Shantha et al. 1988; Rama Rao et al. 1989; Kulkorni and Sharangdher 1990). Rays are caught with bottom set gillnets in Gujarat, northwest India and Cudalore and are abundant on the outer shelf and slope off Kerala and Karnatakta (Devadoss 1978; Kunjipalu and Kuttappan 1978; Sudarsan et al. 1988). Devadoss (1984) indicates that batoids comprise 10% of by catches in Calicut; 90% of the by catch comes from trawlers, 8% from gillnets and 2% from hook and lines. Both sharks and rays are abundant in Lakshakweep and form important by catches in trawl fisheries in Krishnapatnam (Swaminath et al. 1985; James 1988).
Dahlgren (1992) notes that directed fisheries for sharks are developing on a seasonal basis on the east coast of India. About 500 vessels, both sail - powered and motorized, fish for sharks with bottom or drift longlines of the coasts of Orissa Andhra Pradesh and Tamil Nadu. Bottom longlines are usually set in waters 80–150m deep and occasionally as deep as 500m and bull sharks and tiger sharks. The longlines have up to 400 hooks and the meat is usually salted on board during the trip. In Orissa alone, about 200 boats are engaged in drift longlining on a seasonal basis (December - March). The most common species caught by drift longlines are silky sharks and scalloped hammerhead sharks.
Catch composition data are not readily available but the multispecies nature of these fisheries is evident from the literature. Appukuttan and Nair (1988) report that more than 20 species of sharks (mainly carcharhinids and sphyrnids) are commonly caught. Their data for Pamban and Kilakkarai show that Rhizoprionodon acutus, R. oligolinx, Carcharhinus limbatus, C. sorrah, C. hemiodon, Sphyrna lewini and Eusphyra blochii are the most important species. Other species caught are C. melanopterus and Scoliodon laticaudus (Devadoss 1988). Important batoids are: Dicerobatis eregoodoo, Rhynchobatus djiddensis, Rhinobatus granulatus, Himantura uarnak, H.bleekeri, Dasyatis sephen, D.jenkinsii, Aetobatus narinari, A. flagellum, Aetomylus nichofii and Mobula diabolus (Devadoss 1978, 1983; Kunjipalu and Kuttappan 1978).
Local assessments of the state of the fisheries for elasmobranchs exist (Santhanakrishnan 1983, Krishnamoorthi et al. 1986, Devadoss et al. 1988, Sudarsan et al. 1988), but no overall studies exist (Appukuttan and Nair 1988). Devadoss (1983) reports that ray resources off Calicut were apparently overfished by 1980 while according to Reuben et al. (1988) shark and ray resources of Northeast India were still underexploited in 1985. Devadoss et al. (1988) did local assessments using Schaefer's model and made suggestions for effort changes for the different areas. The present situation needs careful monitoring. There appears to be a high level of catches of elasmobranchs in India (peak of 73 500t in 1988) and it is unlikely that such large yields are sustainable over a long periods. The collapse of the neighbouring Pakistani elasmobranch fisheries in 1983 could indicate future catch reductions for the Indian elasmobranch fisheries.
Statistics for the elasmobranch fisheries of Shri Lanka exist since the early 50's. The fishery development has been slow, growing from less than one tonne in 1952 to about 15 000t/yr (Figure 2.2). These fisheries are the smallest among major elasmobranch - fishing countries in the Indian Ocean. Despite this, elasmobranchs are important nationally, contributing 8.76% of the total catches during 1987–1991. This is the highest percentage importance of any elasmobranch fishery in the world. The catch of sharks and rays of Sri Lanka represents 2.42% of the world elasmobranch catch for the period 1987–1991 (Table 2.2).
Information on catch composition is poor for Sri Lanka elasmobranch fisheries. FAO data indicate that catches were commonly grouped in a single “various elasmobranchs” category until 1987.
Since then the category “Carcharhinus falciformis” constitutes the major part of the catch (Figure 2.19). But, information from the National Aquatic Resources Agency (NARA) of Sri Lanka (P. Dayaratne, NARA, Colombo, Sri Lanka, pers. comm. 1992) indicates that C. falciformis comprises 75% of the shark catches, with C. longimanus, C. sorrah, Sphyrna lewini, Alopias pelagicus and Isurus oxyrinchus, high among the remaining 25%.
There are few directed fisheries for elasmobranchs in Sri Lanka. Some estimates (P. Dayaratne, pers. comm. op.cit.) indicate that approximately 85% of the elasmobranch caught is by catch from other fisheries which use mainly bottom and drift gillnets. Both the directed and incidental catches of elasmobranchs come from small - scale fisheries. Drifting shark longlines are used in offshore (>40km from shore) EEZ waters in the directed fishery. Bottom set gillnets operate in coastal areas up to 25km from shore (P.Dayaratne pers. comm. op. cit.). Pajot (1980) reports 26.62% the total catch weight from large - mesh small - scale driftnets off Sri Lanka, consists of sharks and rays. There is some detailed information about the pelagic tuna fisheries off Sri Lanka which catch substantial amounts of sharks. Most of the available information is from the IPTP/NARA tuna sampling programme. The following summary is based mostly on the reports of IPTP (1989), Dayaratne and Maldeniya (1988), Dayaratne and de Silva (1990) and Dayaratne (1993a,b).
Figure 2.19. Elasmobranch catches of Sri Lanka, by species groups, duing 1977-1991 (Data from FAO).
The sampling programme was initiated in Kandakuliya in the northwest, Negombo in the west and Beruwala in the southwest coast of Sri Lanka during 1986 and was extended to two additional locations Matara and Hambantota in the south coast, in 1987. Three types of vessels operate in the pelagic tuna fisheries: small outboard motor boats of about 5m length, diesel motor vessels of about 9m length and 3.5t displacement and the larger 11m long, 11t net tonnage vessels with inboard diesel motors. By far the most numerous are the 3.5 GT vessels numbering about 2000 vessels. They usually carry a crew of four and about 40 panels of net. There are over 1000 of these boats which spend more than 1 day offshore for trip. In contrast, there are only 70 of the 11 GT boats but these usually carry 50–60 panels of net and are capable of making offshore trips of 6–8 days. Gillnets are the most popular gear and they have been used for decades by Sri Lankan fishermen. Each piece of net has 500× 100 meshes which are of 90-180m, most commonly 140–152m, making a total of 3–4.5km of net per vessel. Overall, the yield and catch rate of sharks in this fishery are variable but both show an increasing trend. Total shark catch grew from 1569t in 1986–1987 to 2155t in 1987–1988 in the northwest, west and southwest coasts. For the west and south coasts, total shark catches increased from 3159t to 4374t, to 8676t during 1989–1991. Overall, shark catch rates increased from about 10 kg/day/boat in 1986 to about 35–40kg/boat/day in 1988. These increases in shark yields and CPUE reflect trends seen in the fishery which include expansion of fishing to offshore areas, increase in time spent at sea and a change in fishing gear to involve fewer vessels fishing solely with gillnets and more switching to multiple-gear fishing. The percentage importance of sharks in the catch of each gear combination is 15% for driftnets, 28% for vessels using driftnets/longlines/handlines, 40% for driftnets/longlines/troll lines and 45% for driftnet/longline vessels. Elasmobranch catches for each gear type in 1991 were: driftnet 313t; driftnet/longline 3569t; driftnet/longline/handline 513t and driftnet/longline/troll line 1110t. The sharks in the pelagic tuna fishery are dominated by grey sharks (Carcharhinidae) which constitute 85% of the shark catch, hammerhead (3.5%), thresher sharks (1%), mackerel sharks (0.7%) and other sharks and rays comprising the remaining (10.3%). The weight of sharks is estimated visually. There are plans to include three species of sharks (Carcharhinus falciformis, C. longimanus and Prionace glauca)in the field sampling soon (J. Morón, IPTP, pers. comm. 1993).
In Sri Lanka, at present, there are neither management measures for these fisheries nor are any being considered. So far, there is no evidence of conservation problems or of any species being endangered. Nonetheless, data show that sharks and rays represent an important fishery for Sri Lanka and they should be carefully managed. This summary shows that at least the pelagic fishery is presently in a developing stage.
Statistics show that Japan catches the world's largest amount of elasmobranchs. Catches have followed a decreasing trend after an initial explosive growth from the late 40's when a record 118 900t were caught (Figure 2.2). Despite this reduction, Japan's elasmobranch production of 37 000t was among the top seven in the world in 1991 contributing 4.98% of the total world catch for the period 1987–1991. This is still high when compared with most other countries. Taniuchi (1990) reports that the relative importance of sharks (which traditionally comprise the majority of elasmobranch catches) dropped from 4.3% of the total fish catches in 1949 to 0.3% in 1985 and that both a decline in the relative value of elasmobranchs and a reduction of the Japanese elasmobranch stocks seem responsible for the decline. At present, elasmobranchs constitute 0.31% of the total Japanese catches, one of the lowest among major elasmobranchs-fishing countries (FAO data for 1987–1991). Taniuchi also reports a sharp reduction in catches of Squalus acanthias) in Japan from more than 50 000t in 1952 to less than 10 000t in 1965 and that this likely represents a reduction of the species' stock-size as catches of other sharks did not follow the same trend. However, stock reduction is not the only factor causing Japan's reduced harvests. As the economy of the country grew during the post-war period, changes in purchasing power will have modified consumer preferences which could also change demand for elasmobranchs. This trend is confirmed by the large amounts of sharks that are discarded by various Japanese fisheries.
Japanese elasmobranch production is chiefly a bycatch of other fisheries. Some exceptions are a trawl fishery for skates and rays in the East China Sea, a salmon shark fishery off northeast Japan in the Oyashio Front (Paust, 1987) and a winter fishery in Hokkaido for Raja pulchra (Ishihara 1990). Additionally, small scale coastal gillnet fisheries takes up to 3817t of sharks which accounts for less than 0.01% of the total coastal gillnet catch in Japan (Anonymous 1986). Several trends occur in the data given by Taniuchi (1990) and Ishihara (1990) for the period 1976-1985 (Figure 2.20). Sharks accounted for 83% of the elasmobranch catches of Japan and batoids for 17%; at least 63% of the shark catches were taken as by catch of world-wide tuna longline operations while the remaining 37% came from unspecified sources. Of the average 25 000t/yr of sharks landed by the tuna longline fleet, 58% came from offshore areas, 33% from the high seas and only 9% from coastal waters, presumably the Japanese E.E.Z. The data also show that a shark catch equivalent to approximately 2.8 times the landed shark bycatch of the longline tuna fishery is discarded at sea. Of the approximately 9000t/yr catch of batoids, 50% were caught in the East China Sea, 35% in Hokkaido and 8% in the Sea of Japan. Japan has some of the largest high seas fisheries for tunas and billfishes in the world. These produce substantial bycatches of sharks, only some of which are utilized (See Section 2.3).
Data from FAO for 1977-1991 indicate that sharks are taken mainly in the northwest Pacific (Area 61) where Japanese catches are rapidly declining (Figure 2.21). Approximately 8000t/yr are taken in the rest of the Pacific; this catch has a fairly constant trend and small amounts are also taken in the Indian and Atlantic Oceans. All batoid landings come from the northwest Pacific.
Detailed data on the species composition of the catches are not available from Japanese statistics after 1968. However, Taniuchi (1990) gives data for 1951-1967 and reports piked dogfish Squalus acanthias as the main species in the catch up to 1958 followed by blue shark Prionace glauca and salmon shark Lamna ditropis. The same paper lists 25 shark species captured by tuna longline vessels. Considering the current importance of shark bycatches in longline fisheries to the total shark catch, and data from research cruises reported by Taniuchi (1990), the most important species in the shark catches at present should be, in order, the blue shark (Prionace glauca), the silky shark (Carcharhinus falciformis), the oceanic whitetip shark (C.longimanus) and the shortfin mako (Isurus oxyrinchus). However, discarding practices at sea and the nature of the remaining shark catch that does not come from tuna longliners might affect this. In the East China Sea, Raja boesemani, R. kwangtungensis and R. acutispina are respectively the most important species in the batoid catch (Yamada, 1986).
The meat and the cartilage of Elasmobranchs are used in Japan for traditional dishes, industrial and medicinal uses of liver oil compounds and the skins for making leather. However, Japanese fishermen consider sharks a nuisance as they damage gear and eat hooked tunas and billfishes, and even as competitors for exploitation of valuable fish stocks (Taniuchi 1990). No management measures are known for elasmobranch fisheries in Japan.
The records of South Korean elasmobranch fisheries are intermittent and limited to FAO statistics. South Korea has taken more than 10 000t/yr of elasmobranchs since at least 1948 and yields show an increasing trend varying around 20 000t/yr since the mid-80's (Figure 2.2). Their recent catch of sharks and rays contributes 2.67% of the total world elasmobranch catch (Table 2.2). Given the large fisheries production of South Korea, elasmobranchs are of minor importance representing only 0.66% of the total catches (1987-1991).
Figure 2.20. Elasmobranch catches in different fisheries of Japan during 1976-1984 (S=sharks, B=baltoids, ll=longline) (Data from Taniuchi (1990) and Ishihara (1990)).
Figure 2.21. Elasmobranch catches of Japan, by species groups and region, during 1977-1991 (Data from FAO).
The elasmobranch fisheries of this country are poorly documented - there are no reports on catch composition by species. FAO data (1977-1991) identified two major categories, batoids and “various elasmobranchs”. The latter probably refer to sharks (Figure 2.22). During this period batoids constituted 73% of the elasmobranch catch and were taken chiefly in the Pacific Ocean (94%), with small catches in the Atlantic (4%) and the Indian Oceans (< 1%). Other elasmobranchs came mainly from the Pacific Ocean (88%) and in small quantities from the Atlantic (9%) and Indian Oceans (3%). Although batoids represent the major proportion of the elasmobranch catch according to FAO statistics, the data represent only the actual landings and not discards. South Korean markets may, to some extent, influence the discard procedures at sea. The Korean longlining tuna fleet is known to catch and probably discard great numbers of sharks on the high seas of the world (see Section 2.3).
Figure 2.22. Elasmobranch catches of South Korea, by species groups and region, during 1977-1991 (Data from FAO).
No information on the elasmobranch fisheries of the People's Republic of China exists in FAO statistics. The fisheries agency in China says that no information on elasmobranch fisheries exists. However, China has been exporting increasing quantities of shark fins to Hong Kong during the past few years so that a harvest of sharks must exist, even if as an incidental catch. A rough estimate based on data from the Southeast Asian Fisheries Development Center (SEAFDEC) on shark fins exports to Southeast Asian countries (P. Wongsawang, SEAFDEC, Samutprakan, Thailand, pers. comm. 1992) indicates that China's shark catch apparently grew from less than 100t in 1981 to between 17 000t and 28 000t in 1991, depending on which conversion factor is used (Figure 2.23). These are minimum estimates as an unknown part of the production might not be exported. Actual catches should be much higher. According to Cook (1991), due to the recent relaxation in import and consumer restrictions in China, demand for the traditional shark fin soup has soared, creating extra demand for the product. In addition to the expansion of imports mentioned by Cook, this must be causing increased exploitation of elasmobranchs.
Zhow and Wang (1990) provide some information confirming the existence of fisheries for sharks and rays in the People's Republic of China and give some details. Sharks and rays are caught using driftnets, set gillnets and longlines (there are more than 3.5 million gillnets are used in China) Driftnets range from 30mm to 360mm mesh size but probably those targeting elasmobranchs are near the upper limit of this range. Driftnets target sharks in Xiapu and Jinjiang, Fujian Province. Set gillnets occur in mesh sizes of 30-320mm and are used in shallow waters to target, among many other species, Triakis scyllium and Squalus fernandinus in Haiyang, Shandong Province. Set longlines of different types are used to catch various elasmobranchs. They vary between 388 and 500m in length. Prionace glauca and Carcharhinus spp. are targeted with longlines in Hui'an, Fujian Province, “various sharks” are caught in Yangjiang, Guangdong Province and “various rays” in Changdao, Shandong Province. A variation of longlines called rolling lines ares used to catch rays in Haixin, Hebei province, Minhou, Fujian Province and Rudong, Jiangsu Province. These consist of non-baited sharp hooks narrowly spaced on the main line.
Figure 2.23. Estimated shark catches for the People's Republic of China from fin exports, using 3% and 5% conversion rate (P. Wongsawang, pers. comm.).
Taiwan (Prov. of China) has one of the world's most important elasmobranch fisheries oriented mainly towards sharks. No comprehensive information on elasmobranch catches before the 70's could be found for Taiwan (Prov. of China) but data from the Fisheries Yearbooks of Taiwan (Prov. of China) Area show that large quantities of elasmobranchs have been harvested since the 1950's (Figure 2.2). Total elasmobranch catches fluctuated around 45 000t/yr during 1979–1988. This was followed by a substantial increase of catches in 1989 and especially 1990 when production reached more than 70 000t as a result of increased catches of large sharks (Figure 2.24). These variations probably represent changes in discard practices of the fleet rather than expanded effort. Elasmobranchs comprised 3.5% of the total catches of Taiwan (Prov. of China) from 1987-1991. Large sharks constitute the majority of the catches, approximately 81% of the total elasmobranch catch during 1978-1990. Small sharks account for approximately for 14%, while rays are of little importance contributing about 5%. Main elasmobranch species in the catch are hammerhead sharks (Sphyrna lewini, S. zygaena), grey sharks (Carcharhinus plumbeus, C. falciformis), mako sharks (Isurus oxyrinchus), blue sharks (Prionace glauca) and thresher sharks (Alopias superciliosus, A. pelagicus) (C.T. Chen, National Taiwan Ocean University, pers. comm. 1992).
Figure 2.24. Elasmobranch catches of Taiwan (Prov. of China) by species groups, during 1978–1990 (Data from FAO).
Most of the shark catch from Taiwan fisheries are obtained outside their own waters by the various far-seas tuna fleets. During 1988-1990, approximately 85% of the large shark and 70% of the small shark catches came from these operations. In contrast, most of the ray catch (53%) for the same period were caught in Taiwanese waters.
The Taiwanese far-seas fleet is difficult to monitor as it operates in all the oceans of the world and is composed of many sizes and types of vessels (i.e. longliners, driftnetters, purse seiners) (Ho, 1988). Significant shark catches are taken by large-scale driftnetters targeting sharks particularly in Indonesian waters of the Arafura, Banda and Timor Seas.
Taiwan (Prov. of China) prosecuted an important fishery for sharks in Northern and North Western Australia waters from 1972 to 1986 for which Millington (1981) Okera et al. (1981) and Stevens (1990) provide some information. This was mainly composed of driftnetters setting multifilament nylon nets varying between 3 and 12km length, 140-190mm mesh size and 17-30m deep. Vessels size ranged between 160 and 380 GT. Further, Taiwanese pair trawlers fishing for demersal fish took shark bycatches on approximately the same grounds as the driftnetters. The catches of driftnetters were 80% sharks. Of these, Carcharhinus tilstoni and C. sorrah were the main component (55% of total catches), the remaining were tuna and mackerel. Between 3500 and 14 800t/yr of sharks were taken by these driftnetters during the period 1975-1980. Catches from pair trawlers averaged approximately 2000t/yr of sharks; up to 7000t were taken in 1974. Limits on the number of vessels, and fishing areas and a catch quota of 7000t were imposed on this fishery in 1979 by the Australian Government. The Taiwanese shark driftnet fleet left the fishery in 1987 following the imposition of a maximum gillnet length of 2.5km by the Australians which made the fishery unprofitable (Stevens 1990) but have since continued the fishery in Indonesian waters. At least 7000t/yr of sharks were taken by the Taiwanese fleet in the Australian EEZ before 1987. It is unknown how much they presently catch in Indonesia. If the SEAFDEC figures reported for Taiwanese large-scale gillnet shark catches correspond to the fishery in Indonesian waters, then 19 636t were taken there in 1987. Also, bycatches of sharks in other important large-scale Taiwanese fisheries, for example the tuna longline fishery, the Indian Ocean driftnet fishery and North Pacific squid driftnet fishery, must account for part of the shark catches of this country but are so far unrecorded. These fisheries are further discussed in Section 2.3.
Data from the Fisheries Yearbooks of Taiwan Area, during 1988-1990 show that the main fishing localities for large sharks were Ilan Hsien and Pingtung Hsien. These areas account for 32% (2109t/yr) and 49% (3246t/yr) of the large sharks caught in Taiwanese waters. Keelung Hsien was the main site for catches of small sharks and rays providing 37% (991t/yr) and 73% (875t/yr) of the local catches of each group respectively.
Most of the Taiwanese shark catches are taken by large-scale fisheries, particularly with longliners. According to SEAFDEC data, about 90% of the domestic elasmobranch catch of 9529t (those taken in the South China Sea Area) in 1988 came from large-scale fisheries. For sharks, large-scale longlines and hook and lines accounted for 62% of the catches while gillnets and otter trawls accounted for less than 20% each (Table 2.7). Only 5% of the shark catch came from small-scale gillnet fisheries and less than 1% from traps and longlines. For rays, otter trawls were the most important large-scale gear with 23% of the catch, but gear classified as large-scale “others” took 58%. Gillnets took to 7% of the small-scale catch. The remaining 11% of ray catches was taken using small-scale gillnets and traps.
It is unknown if any stock assessment has been done for the Taiwanese fisheries. Nevertheless, elasmobranch stocks in Taiwan (Prov. of China) are believed to be overexploited and tiger sharks (Galeocerdo cuvieri) are considered to be an endangered species (C.T. Chen, pers. comm. op. cit.). Despite this, no management measures exist or are being considered for Taiwan's elasmobranch fisheries.
|TAIWAN||PENINSULAR MALAYSIA||INSULAR MALAYSIA|
|TYPE OF FISHERY AND GEAR||WEST COAST||EAST COAST||SABAH||SARAWAK|
|Hook & line||62||0||-||-||-||-||-||-||-||-|
|TOTAL CATCH (mt)||8588||941||1359||6125||1111||2303||910||596||1872||2546|
Philippine's elasmobranch catches were of minor importance before the late 1970's and although variable, expanded until 1986 stabilizing around 17 000t/yr (Figure 2.25). From 1987-1991 they comprised only 0.8% of the total national catches. SEAFDEC data show rays to be slightly more important than sharks in the catches representing an average 53% of the elasmobranch yields during 1977–1991, although both groups showed a growing trend the catches during this period. Philippine catches account for 2.63% of the worldwide elasmobranch catch.
Judging from the 1988 catches (17 879t), small scale fisheries provide the large majority of elasmobranch catches in Philippines (Table 2.8). In Luzon, large scale trawlers accounted for 30% of the local shark catches but only 6% of rays, with purse seiners taking around 3% of both groups' catches. In Visayas, trawls were the main gear in large scale fisheries for rays (23%) but accounted for only 1% of that of sharks. Large scale purse seining took 11% and 8% of the shark and ray catches respectively in that area. Catches from small-scale fisheries for both sharks and rays in Luzon and for sharks in Visayas were mainly taken by hook and line and longlines (38%–76%) but also by gillnets (8%–30%). The reverse was the case for catches of rays in Visayas where gillnet catches were greater than those from hook and line and longline (42% vs. 22%). Small contributions to the catches of both fishes were made in Visayas and Luzon by “other gear” (< 13%). Minor catches of rays were also taken with traps (< 8%). Small scale fisheries took all the elasmobranch catches in Mindanao. The main gear was with gillnets in the case of rays (81%) and hook and line for sharks (57%). Small scale gear, classified as “other”, were the second most important method of catching both groups (28% of sharks, 10% of rays). Gill nets took 15% of the small-scale shark catches and traps less than 1%. For rays, hook and line and longlines were the third most important gear in this area taking 7% of the catch. Traps and otter trawls took little.
The composition of batoid and shark catches by area is shown in Figure 2.25 based on SEAFDEC data. Mindanao is the most important area for the catches of both sharks and rays, averaging 3185t/yr (24% of total elasmobranch catches) and 2724t/yr (21%) respectively. Ray catches have generally grown there while shark catches have been variable. Luzon is the second area in importance with 1993t/yr of sharks (15%) and 2312t/yr of batoids (18%). Shark catches in Luzon have decreased from the levels of the late 70's while batoid yields have recently increased after a decline in catches in the early 80's. Production of sharks and rays in Visayas is the lowest in the Philippines with averages of 1108t/yr (8%) and 1856t/yr (14%) respectively; yields of both groups show the same behaviour for batoid catches in Luzon.
Little is known about the species composition of elasmobranch catches in the Philippines. Warfel and Clague (1950) report tiger sharks to be the major catch of shark longlines around the Philippines from exploratory fishing. Other sharks found in the survey include at least six species corresponding to the genus Carcharhinus, plus Sphyrna zygaena, Scyliorhinus torazame, Hexanchus griseus and an unidentified nurse shark. The species taken by gillnets were Pristis cuspidatus and Rhynchobatus djiddensis. Encina (1977) reports on a new dogfish fishery catching Squalus acanthias and Centrophorus spp. around the Philippines, primarily directed prosecuted for squalene oil extraction.
Figure 2.25. Elasmobranch catches of Philippines, by species groups and region, during 1976– 1990 (Data from SEAFDEC).
Now, one of the more modest major elasmobranch fishing countries in Southeast Asia, Thai catches grew considerably in the 1960's but have declined since the early 1970's (Figure 2.2) mainly as a consequence of over-exploitation by trawlers in the Gulf of Thailand (Menasveta et al. 1973, Pope 1979). In later years, there were signs of an apparent recovery but catches have, since 1988, dropped again and the present state of the stocks is uncertain. Sharks and batoids represent a minor resource in Thailand and contributed only 0.43% of the total production during 1987–1991.
Rays, taken as a bycatch by trawlers, dominate the elasmobranch catches. SEAFDEC data show that average catches of rays for the period 1976–1991 accounted for 64% of the elasmobranch production, while sharks were only 36%. Estimates of the Thai Department of Fisheries show that approximately 95% of the shark catch is composed of individuals smaller than 1.5m TL, mainly Carcharhinus spp., while the main batoid species in the catch are Dasyatis spp. and various eagle rays. (P. Saikliang, D.O.F. pers. comm. 1991).
Thai elasmobranch fisheries are chiefly a large-scale activity. Of a total of 11 438t of elasmobranchs taken in 1988 by Thailand, most of the catches on both coasts of the country came from large-scale trawlers. Otter trawls caught 63% and 82% respectively, of the shark and ray catches of the Gulf of Thailand and 92% and 64% of those from the Andaman Sea coast. Further, pair trawlers in the Gulf of Thailand took around 10% of both fish catches (Table 2.8).
|TYPE OF FISHERY AND GEAR||LUZON||PHILIPPINES VISAYAS||MINDANAO||THAILAND|
|Hook & line||2||-||-||-||-||-||-||-||-||-|
|TOTAL CATCH (mt)||1513||3132||1742||1924||3879||5689||3436||5963||408||1631|
In the Gulf of Thailand, large-scale gillnets accounted for 22% of shark catches but only 1% of the rays. Purse seiners caught small catches of both fish. In the Andaman Sea small shark catches were taken by large-scale gill nets. Small-scale elasmobranch fisheries in Thai waters are relatively important for their catches of rays by gill nets in the Andaman Sea coast where they caught almost 30% of the local ray catches. Small catches (less than 1 to 7% of local catches) of both fishes are also taken in small-scale hook and line and longline fisheries in both coasts. In the Gulf of Thailand, small-scale gillnets take only small catches of sharks and rays.
The main fishing grounds for sharks and rays is the Gulf of Thailand. During 1976–1989 catches from the Gulf averaged 2955t/yr of sharks (28% of all elasmobranchs caught) and 4885t/yr of rays (46%) while the Andaman Sea produced only 1042t/yr of sharks (10%) and 1709t/yr of rays (16%). The trend of shark catches during this period showed a slight increase in the Gulf of Thailand and a decrease in the Andaman Sea. Ray catches from the Gulf of Thailand increased considerably and diminished in the Andaman Sea (Figure 2.26).
No recent stock assessments for the area are known. Studies from the early 1970's based on swept area estimates of the 1963 and 1966–1972 research cruises (Menasveta et al. 1973) indicated stock biomasses of 2880t for sharks, 4404t for rays and 1988t for rhinobatids in the whole Gulf of Thailand and an estimated 5000t potential yield for all elasmobranchs. The study identified large reductions in biomasses of rays over that period and concluded that elasmobranch stocks were “heavily exploited”, if not overexploited. However, these estimates might have been too low as total Gulf catches of elasmobranchs from Thailand and Malaysia were 10 439t in 1977, 10 959t in 1978 and 7621 in 1979. They maintained a level of about 8000t/yr for another 6 years rising above 10 000t/yr in the late 1980's. Nevertheless, the reductions in catch rates (Pope, 1979) show that the stocks of both sharks and rays have declined dramatically in the area.
The elasmobranch fisheries of Malaysian and those of Philippines and Thailand are among the smallest in Asia. Catches of sharks and rays comprise only 2.46% of the world catch of this group. The development of the fishery in Malaysia showed a slow growth from 1961 to the current level of 15 000t/yr (Figure 2.2). Elasmobranchs currently represent 2.2% of the total catch of Malaysia. Rays are more important than sharks in the catches. SEAFDEC data indicate that from 1976–1991 rays represented, on average, 60% of the elasmobranch catch and sharks the remaining 40%. Catches of sharks showed overall a slight declining trend while ray catches increased, mainly from 1986–1991 (Figure 2.27). The main species in the ray catches are Rhyncobatis djiddensis (which together with other ray species is processed as “shark fin”), Gymnura spp. and Dasyatis spp. Scoliodon sorrakowa, Chiloscyllium indicum and Sphyrna spp. are the most common shark species caught (C. Phaik, pers. comm. 1992).
Elasmobranch caught in Malaysia are predominantly are predominately bycatch of trawl fisheries; only a small amount taken in directed fisheries. Almost 95% of the catches come from trawl fisheries while small-scale directed fisheries take the remaining 5%. Of the 16 822t of elasmobranchs caught by Malay fisheries in 1988, the great majority were taken by large -scale fisheries, of which trawl fisheries were the most important. In both coasts of Peninsular Malaysia and the Sabah coast, between 60% and 70% of the local shark catches were taken with trawls, while those of rays were in the order of 72–93%. Purse seines caught less than 1% of sharks in Peninsular Malaysia. In the waters of Sarawak, 70% of local ray catches came from large scale otter trawls, but this gear only contributed 30% of the shark catches. In this area, other largescale gears accounted for less than 1% of catches of sharks and rays.
Malaysian small-scale fisheries for elasmobranchs are not as important as large-scale fisheries for their contribution to total elasmobranch catches. In Sarawak, during 1988, this sector took 70% of the local shark catches using mainly gill nets (54%), longlines and hook and line (15%) with traps making a very small contribution (Table 2.7). Rays taken by small-scale fisheries were caught by hook and lines and longlines (17%) and gillnets (11%); small catches were also taken with traps. For both coasts of Peninsular Malaysia and Sabah, small scale gill nets fisheries took between 15% and 28% of the shark catch while hook and line and longlines accounted for about 9% of the catch in Peninsular Malaysia and 25% in Sabah. Catches of rays from small-scale fisheries in Sabah and off the west coast of Peninsular Malaysia were taken mainly by hook and line and longlines and to a lesser extent by gillnets traps and other gear. The opposite occurred on the east coast of Peninsular Malaysia where most of the small contribution (5%) of small scale fisheries to the total rays catch came from gillnets.
Figure 2.26. Elasmobranch catches of Thailand, by species groups and region, during 1976-1990 (Data from SEAFDEC).
Figure 2.27. Elasmobranch catches of Malaysia, by species groups and region, during 1976-1990 (E.P.M.=eastern peninsular Malaysia, W.P.M.=western peninsular Malaysia) (Data from SEAFDEC).
As a consequence of the by catch of elasmobranchs, the most important fishing grounds are those of the trawl fishery - mainly peninsular Malaysia and Sarawak. During 1976–1989 sharks were taken mainly in Sarawak (1869t/yr or 15% of total elasmobranch catch), the west (1363t/yr or 11%) and east coasts of Peninsular Malaysia (1169t/yr or 9%) and in smaller quantities in Sabah (778t/yr, 6%). Sharks catches in these areas decreased in west Peninsular Malaysia but had relatively sustained yields in Sarawak and Sabah and were variable in east Peninsular Malaysia (Figure 2.27). For rays, the west coast of Peninsular Malaysia is the most important fishing area (3457t/yr, 28% of total elasmobranch catches) followed by Sarawak (2004t/yr, 16%) and the east coast of Peninsular Malaysia (1324t/yr, 11%), with Sabah contributing only 573t/yr (5%). The data show in increase in ray catches on both coasts of Peninsular Malaysia, relative stability in Sabah and strong variability in Sarawak. There are no existing management measures for elasmobranchs and the licence restrictions for trawlers only indirectly limit the catches, mainly those of rays.
Statistics for the elasmobranch fisheries of Indonesia were not recorded before 1971 but show a tremendous increase since the beginning of the FAO records. Indonesia holds the highest sustained rate of development for any elasmobranch fishery and currently has the largest fishery in the world. Indonesian catches amounted to almost 80 000t and there are no signs of levelling off (Figure 2.2). Indonesian fisheries represent 10.18% of the world's elasmobranch catch. Despite this, elasmobranchs are of only moderate importance in Indonesia, contributing 2.41% to Indonesian landings during 1987–1991. Contrary to most major elasmobranch fishing countries in the region, which harvest larger quantities of rays than of sharks or similar quantities of both, catches in Indonesia are dominated by sharks, which accounted for 66% of the average elasmobranch catches during 1976–1991.
SEAFDEC data (1976–1989) show that the most important areas for shark fishing in Indonesia are situated in the western part of the country, i.e. Java (9727t/yr on average and 21% of total elasmobranch yields), Sumatra (7837t/yr, 17%) and Kalimantan (5870t/yr, 12%) with the eastern provinces of Bali-Nusa Tengara, Sulawesi and Molluca-Irian Jaya, accounting for 1796t/yr (3.8%), 3157t/yr (7%) and 1983t/yr (4.2%) respectively. This pattern is similar for batoid catches except that Sumatra is the top producer with 6404t/yr (13% of total elasmobranch catches), followed by Java with 4670t/yr (11%) and Kalimantan with 2987t/yr (6%). In the eastern provinces Sulawesi is first with 1329t/yr (3%), Bali - Nusa Tengara second with 957t/yr (2%) and Molluca-Irian Jaya third with 518t/yr (1%). The catches of sharks and rays show increasing trends over the period in all provinces, except those of sharks in Molluca-Irian Jaya and both groups in Bali-Nusa Tengara which had rather poor development (Figure 2.28). These last two areas could be the most suitable for future increases in the fishery.
In addition to the Indonesian catches, large quantities of sharks have been harvested by the Taiwanese driftnet vessels in Indonesian waters since they abandoned the Australian EEZ in 1987. This fleet was capable of taking at least 7000t/yr of sharks and catches in the area between north Australia and Indonesia were in the region of 25 000t/yr before 1979 (Stevens, 1990). In the light of these combined catches, it is surprising that yields from Indonesia keep increasing annually. There are no apparent research or management programmes for elasmobranchs in Indonesia and the question of the potential of shark fisheries in the area becomes more intriguing as catches keep growing. Much attention should be paid to this fishery if catches are to be sustained.
Figure 2.28. Elasmobranch catches of Indonesia, by species groups and region, during 1976-1990 (B=batoids, S=Sharks) (Data from SEAFDEC).
Elasmobranch fisheries in Australia are small and barely classifiable as “major fisheries” having only temporarily exceeded 10 000t/yr during the late 1980's (Figure 2.2). They only contribute 1.46% to the world elasmobranch catch (1987–1991). Nevertheless, Australian shark fisheries are among the most documented and managed elasmobranch fisheries in the world. This is probably directly related to the importance of elasmobranchs in the catches of Australian fisheries. FAO data for 1987–1991 show that elasmobranchs contribute 4.8% of the landings in Australia, the third highest percent importance in the world. Further, these are mature fisheries and from part of the fishing tradition of the country. Stevens (1990) reviews Australian shark fisheries and gives their history back to the end of the 19th century when fisheries for school sharks' liver oil and fins already existed in southeastern Australia.
FAO data are not presented by species or species groups and only the geographical distribution of the catches is discernible. The bulk of catches come from the Area 57 probably reflecting catches from the southern shark fishery for Mustelus antarcticus and Galeorhinus galeus. Small catches of elasmobranchs come from Area 81. Catches in Area 71 are negligible (Figure 2.29).
Historically, the most important elasmobranch fishery in Australia has been the southern shark fishery which provides the major part of the elasmobranch catches of the country. Walker (1988), Anonymous (1989) and Stevens (1990) summarize the situation for this fishery. School sharks, (Galeorhinus galeus), were the original targeted species at least since 1927, when records began to be taken regularly. Other important species in the fishery are the gummy shark (Mustelus antarcticus), the sawsharks (Pristiophorus cirratus and P. nudipinnis) and the elephant fish (Callorhynchus millii). Management of the fishery began in 1949 when a minimum size of 91cm TL was introduced for school sharks in Victoria. Protection of nursery areas in coastal lagoons followed later. The fishery expanded from coastal to offshore operations in the mid-1940's and catches gradually grew until 1969. The fishery suffered a temporary reduction in yields following the combined effect of the introduction of monofilament gillnets and a ban in Victoria of school sharks longer than 104cm TL due to impermissibly high mercury concentration in their flesh. The introduction of gillnets was intended to boost the decreasing catches of school sharks but this also brought about big bycatches of gummy sharks which had previously been regarded as undesirable species. Because of the size restrictions on school sharks the gummy sharks displaced school sharks as the main species in the catches. Soon, revised size limits allowed school sharks between 71–112cm TL to once more be taken in the Victorian fishery and total catches rose to a peak of 3754t (dressed weight) in 1986 with both species contributing approximately equally to the catch. Thereafter, catches slowly declined.
Most of the catch in the southern shark fishery is taken with monofilament gillnets and longlines but some catches is also taken by trawlers. Gillnets vary in size geographically and the mesh size ranges from 15cm (legal minimum) to 20.23cm with 17.78cm being most common. Gillnets used are typically 1.7m deep with a hanging coefficient of 0.6 (Kirkwood and Walker 1986). Gillnets are the main source of total shark catches (90% of the gummy shark and approximately 75% of the school shark catches). Longlines are typically 10km long and rigged with several hundreds of hooks. Although less important than gillnets their utilization has grown lately, especially in Tasmania. The most important fishing grounds for Mustelus antarcticus are primarily Bass Strait and secondarily in South Australia. The opposite is true for Galeorhinus galeus which, until recently, almost equalled those of the other areas in the Tasmanian catches. The contributions to the total shark catches of 1987 by gear and area are: Bass Strait, gillnets 47.3%, longlines 7.4%; South Australia, gillnets 27.3%, longlines 1.3%; Tasmania, gillnets 10.9%, longlines 10.4% (Anonymous 1989).
The fishery is a model for management of elasmobranch resources. Fishing effort has expanded in all areas and drops in gillnet CPUE (kg/km/hr) for both species have led scientists to suspect that both stocks are declining. As a result, a monitoring program and a special research group have been set up to study the fishery and several projects funded by the fishing industry and government agencies are being carried out. Their approach is comprehensive with research ranging from biological studies (Moulton et al. 1992) and the construction of databases and specific simulation models for the management of the fishery (Walker 1992, Sluckzanowski et al. 1993) to economic analyses (Campbell et al. 1991). The biology of the species is well known and suggests separate breeding populations for each species. However, concerns have been raised about the spatial structure and dynamics of the populations. Present investigations concentrate on the spatial dynamics of the stocks and the vulnerability of juvenile school sharks to commercial and sport fisheries in nursery areas of Tasmania. The recent concerns about overexploitation of the stocks has led to effort reductions by about a 50% through an elaborate licensing procedure. Longline effort was not considered in the scheme and this type of effort grew rapidly as a result of the restrictions imposed to gillnetters. It caused the overall effort reduction to fall short of that intended.
There is a smaller shark fishery operating in the lower western and south western coast of Western Australia. Catches are dominated by Furgaleus macki and Mustelus antarcticus but substantial catches of Carcharhinus obscurus are also taken (Lenanton et al 1990). Catches are about 1600t/yr and about 10% of the Australian catch of gummy shark comes from this fishery. Management measures include licence limitations, gear restrictions and a recent prohibition of shark fishing in waters from Shark Bay northward to North West Cape (Anonymous 1992).
The northern Australia shark fishery was started in 1974 by Taiwanese gillnetters exploiting sharks, tuna and mackerel in offshore areas of the Arafura sea. Taiwanese pairtrawlers fishing in the same areas also took sharks as by catch (see Section 184.108.40.206). Sharks comprise approximately 80% of the catch with 55% being Carcharhinus tilstoni and C. sorrah. At the beginning of the 1980's Australian fishermen became interested in these resources and small fisheries spread in inshore waters from the Northern Territory to the north of Western Australia and Queensland. Catch composition is similar to that of the offshore Taiwanese fishery and landings have fluctuated between 50 and 400t/yr (Stevens 1990). Although stocks declined due to overexploitation by the Taiwanese fleet, with the fleet move to Indonesia in 1987 the stocks are believed to be recovering. No management measures for the small domestic fishery are thought necessary at present. This fishery has been closely monitored and several research projects have been conducted by the Northern Territory Department of Primary Industry and Fisheries and the Commonwealth Scientific and Research Organisation (CSIRO).
The future development of a shark fisheries in North Australian waters is limited by high concentrations of mercury and selenium in most species of carcharhinids and sphyrnids. Lyle (1984) estimated that only 49% of the catch in weight could be retained if the maximum permitted level of mercury is 0.5 mg/kg. Further, market restrictions have prevented tropical catches from entering the main market for shark meat in Melbourne (Rohan 1981). Some recent arrangements have been made in the northern shark fishery to prevent overexploitation. Several restrictions have been introduced in different areas under Commonwealth jurisdiction since January 1992.
Elasmobranch fisheries in New Zealand remained under 10 000t/yr until recently. Although current catches are not much larger there has been an increasing trend since the late 1970's (Figure 2.2). Elasmobranch fisheries are moderately important for New Zealand with catches making 2.19% of the total fishery production during the last 5 years reported. New Zealand fisheries for sharks are another example of continuing research and management. On a global scale, these fisheries are small, contributing only 1.73% to world elasmobranch production (Table 2.2).
According to FAO data for 1977–1989 the yields of the different elasmobranch groups in New Zealand are quite variable. Dogfish (mostly Squalus acanthias) catches show a tremendous increase while catches of smoothhounds show a decline. Batoid and elephant fish catches grew moderately and the catch of grey sharks (mostly tope) greatly expanded and contracted during this period (Figure 2.30).
Recent information of the N.Z. Ministry of Agriculture and Fisheries shows that during 1989–1992, approximately 15% of the catch consisted of elephant fishes (Callorhinchus milli)and chimaeras (Hidrolagus spp.), 18% of tope shark (Galeorhinus galeus), 12.5% of rig (Mustelus lenticulatus), 33% of piked dogfish (Squalus acanthias), 17.5% of the skates Raja nasuta and R.innominata. The remaining 4% consisted of 13 species of large and deepwater sharks and at least 3 species of batoids. About 40% of the total is by catch of trawl fisheries while the other 60% is mainly taken directly with longlines and setnets. Elephant fishes are caught mainly off Canterbury; tope sharks and rigs are taken all around New Zealand.
Figure 2.29. Elasmobranch catches of Australia, by FAO statistical areas, during 1977-1991 (Data from FAO).
Figure 2.30. Elasmobranch catches of New Zealand, by species groups and region, during 1977-1991 (Data from FAO).
Francis and Smith (1988) analyze the catches of rig around New Zealand and summarize some information about this fishery. The rig fishery is strongly seasonal concentrated during the austral spring and summer months. The catches are mostly exported to Australia. Almost 90% of the catches were taken as by catch of trawl fisheries during the mid 1960's, but the increase in demand and introduction of monofilament gillnets changed the pattern of exploitation and presently setnets account for 80% of the landings. Francis and Smith report that CPUE declined in three of the five zones analyzed during 1974–1985 and that in several areas stock sizes appear to be down to one third of their original sizes. Presumably, these are part of the reason for the imposition of management regulations in this fishery.
Management measures for the main elasmobranch species in New Zealand include TACs, a percentage of which go to ITQ holders. In 1992 the TACs were 636t for elephant fishes, 2070t for rig and 3087t for tope shark (Annala 1993). Catching basking sharks is prohibited and there are current proposals to include more elasmobranch species under the quota management system. Research in New Zealand has concentrated on rig and piked dogfish (Francis and Mace 1980, Hanchet 1988, Francis 1989, Massey and Francis 1989, Hanchet 1991, Francis and Francis 1993).
Some small quantities of livers from deep water squaloid sharks are currently utilized from the bycatches of the orange roughy (Hoplostethus atlanticus) deep trawl fisheries of New Zealand (King and Clark 1987), although large quantities of the sharks are also discarded at sea (see Section 2.3). Results from research cruises indicate that the stock of these deep sea sharks could sustain yields of no more than 2250t/y.