This section will review straddling stocks on a sub-regional basis. It is recognized from the onset that the biological differences between the two legal categories (i.e. highly migratory stocks and straddling stocks) are not always clear. In the preceding section many species of high-seas character have been noted which could be included in either group. The oceanic cephalopods require particular attention in this respect. Their ocean-wide distribution and oceanic character makes them one of the best examples of high seas resources (Maps 9 and 10 a,b). The neritic squids (Loligo spp., Illex spp. and Todarodes spp.) are known to undertake migrations of a few hundred kilometres (Caddy, 1989), usually alongshore, on deep shelves and slopes, easily straddling “out” when these extend beyond 200 miles. The stock structure and migration patterns of oceanic squids are much less well known but, because of their short lifespan (squids are essentially annual species), it can probably be assumed that migrations are of limited range, possibly as extended as those of the neritic squids. For the purpose of this paper and pending more precise information on their migrations, oceanic squids (Ommastrephidae) might be considered good candidates for straddling “in” stocks with a very significant high seas component. Of the ten genera of this family, six support fisheries and it is believed that the family accounts for half of the world's cephalopod catch. It is sub-divided in three sub-families. Two of them are essentially neritic (Illicinae and Todarodinae) and one is more oceanic (Ommastrephinae).
Map 9: Distribution of neritic squids (from Garcia and Majkowski, 1992. Reproduced by courtesy of the Law of the Sea Institute, Univ. Hawaii)
Map 10a: Distribution of oceanic squids (from Garcia and Majkowski, 1992. Reproduced by courtesy of the Law of the Sea Institute, Univ. Hawaii)
Map 10b: Distribution of oceanic squids (continued) (from Garcia and Majkowski, 1992. Reproduced by courtesy of the Law of the Sea Institute, Univ. Hawaii)
A more complete analysis of the potential offered by oceanic squids is given in Garcia and Majkowski (1992) from which the following information is drawn. Juveniles of oceanic squids are exploited mainly by set-nets and seines on the shelf, while feeding adults are exploited by jigging vessels (and, in the past, by large-scale pelagic driftnets) mainly in the North Pacific and the Southwest Atlantic. Catches of squids increased from 745 000 t in the early 1970s to about 2 million t in the late 1980s and early 1990s. Catches of oceanic squids (Ommastrephidae) have oscillated between 250 000 and 460 000 t during the same period.
While knowledge on neritic squids has improved since the first review of world resources potential by FAO (Gulland, 1971), that on oceanic squids outside the Pacific remains very scanty even for the major Ommastrephidae. Very rough speculations (Gulland, 1971) indicated that potential of oceanic squids would reach “a few million tons but not so much as 100 million tons”. The following table (from Garcia and Majkowski, 1992) summarizes the situation by major species and ocean region.
|Oceans and Species||Potential (tons)|
|Ommastrephes bartrami||380 0001|
|Ommastrephes borealijaponica||130 0001|
|Symplectoteuthis oualaniensis||100 0002|
|Gonatopsis borealis||6 0001|
|TOTAL Ommastrephidae||500 0003|
|TOTAL Squids||5 000 000–50 000 0003|
|Dosidicus gigas (California)||300 0004|
|Dosidicus gigas (Total South)||1 000 000–1 500 0004|
|Symplectoteuthis oualaniensis||2 000 0005|
|Ommastrephes pteropus||1 600 000–2 500 0006|
|Mesonychoteuthis hamiltoni||1 000 000–1 500 0007|
|ALL OCEANS||< 100 000 0008|
|90 000 0007|
1) Okutani, 1977;
2) Voss, 1973;
3) Jefferts, 1986;
4) Roper et al., 1984;
5) Zuev and Gutsal, 1990;
6) Zuev et al., 1990;
7) Klumov and Yukhov, 1975;
8) Gulland, 1971.
Most of these figures should be taken with caution but they indicate that there is a large potential if fishing can be economically developed. The status of these resources is not very well known. Symplectoteuthis oualaniensis in the Central Eastern Pacific is very lightly exploited and the Indian Ocean stock is probably close to virgin. The stock of Dosidicus gigas in the Southwestern Pacific Ocean must be very lightly exploited and the stocks of Mesonychoteuthis hamiltoni and Gonatopsis borealis are also virgin. The status of Ommastrephes bartrami is given in section 3.1.
In this region, the shelf is one of the widest in the world and it supports resources which are among the world's richest.
The Alaska pollock (Theragra chalcogramma) is widely distributed in the North Pacific (Bering Sea, Sea of Okhotsk) and is a good example of an important straddling stock. Its stock structure is not clear and there may be twelve stocks in the Western Pacific region (Chikuni, 1985). The fish is pelagic or semi-pelagic in its five first years of life and develops as a demersal resource when it matures sexually. Total catches increased steadily in the North Pacific from 300 000 t in the 1950s to about 4 million t in the early 1970s and 6.7 million t in the late 1980s (Table 1). These are the highest catches for a single species in the North Pacific (except recently for sardines). The stock has been exploited by the USA, ex-USSR, China, Japan, Republic of Korea and Poland. In the late 1980s, about 25–30% of the landings from the Bering Sea came from the Donut Hole, a small high seas enclave in this sea (Map 11). The Peanut Hole is another small high seas enclave in the Sea of Okhotsk. The resource has been considered globally fully fished (Chikuni, 1985). The condition of the Northeast Pacific stock is considered good with a biomass of 8.8 million t (Arnason and Trondsen, 1989). The management of this resource in the international waters of the Bering Sea (Donut and Peanut Holes) is a source of controversy. The Bering Sea biomass, estimated at 13 million t, has apparently decreased at an annual rate of 10% (Shapiro, 1990) and fishing rates have been excessive. Another problem is related to the possible effect of increased exploitation of pollack on food supply of marine mammals (cetaceans, Stellar sea lions). It can be argued that the stocks were plundered. Catches in the Donut Hole have decreased from 1 million t in the late 1980s to 22 000 t in 1992. In August 1992, the USA, Russia, Japan, Poland, Republic of Korea and China have agreed to a harvest moratorium after most of the biomass has apparently disappeared (Munro, 1993).
Jigging fisheries on the flying squid Ommastrephes bartrami started with a catch of 14 000 t in 1974 following overfishing of the Todarodes in the Sea of Japan in the 1960s (Osako and Murata, 1983) and the search for new grounds in the high seas, following the establishment of EEZs in the early 1970s. The fishery extended offshore between 1974 and 1980 reaching 170°E, and oscillates seasonally between 39°N and 49°N (Jefferts, 1986). Driftnetting started in 1978 close to Japan and expanded rapidly into the central part of the North Pacific between 170°E and 160°W. By 1986 Japan alone accounted for approximately 150 000 t and it was estimated that Korean and Taiwanese vessels catch a similar amount (Beamish and McFarlane, 1989). The total catch would therefore be of the order of 300 000 t, a value close to its total estimated potential. The fishery was regulated by Japan after conflicts between jiggers and gillnetters in 1979, and gillnets were confined at more than 100 km offshore. Management includes by-catch limitations but international conflicts with salmon and tuna fisheries are intense and difficult to resolve in the absence of an international body with competence on all species concerned. Jefferts (1986) states that stocks have probably been fully fished since 1978. Jefferts (1986) also mentions that the Northwest Pacific stock of Ommastrephes bartrami may have been fully fished since 1978. Beamish and McFarlane (1989) note that the total estimated catch of this species in the North Pacific, of the order of 300 000 t, was close to the estimated total potential. The resource may therefore be fully exploited in the North Pacific.
Other species likely to be straddling out on the North Pacific shelf and slope are the cephalopods (Onychoteuthys borealjaponica and Gonatopsis borealis), the Pacific Ocean perch (Sebastes alutus) already overfished in the 1960s (Chikuni, 1985), the pelagic armorhead (Pentaceros richardsoni) and the alfonsin (Beryx splendens).
Map 11: The Donut Hole in the Bering Sea (North Pacific)
In the Northeast Pacific, the jack mackerel (Trachurus picturatus symmetricus) can be found all along the North American coast and is known to exist far offshore. There is a coastal fishery for T. picturatus symmetricus off California and the species is also taken off Mexico. It is a by-catch of the North American salmon troll fishery but discarded at sea. It is finally exploited by the long-range foreign trawl fleets targeting at the Pacific whiting (MacCall et al., 1980). Landings have varied greatly between 10 000 and 73 000 t since the 1940s in relation to the status of the sardine fishery. They decreased from 28 000 t on average in 1975–79 to about 10 000 t in the late 1980s. The species is known to exist very far offshore, beyond 200 miles off the USA and Canada.
Spawning population biomass of T. picturatus symmetricus was estimated to be at least 1.5 million t (MacCall et al., 1980). The potential is not known with precision and may be between 50 000 and 290 000 short tons.
Two types of straddling resources problems are encountered in this area. On the one hand, continental areas (Australia) and large islands (New Zealand) have shelves of sufficient extension to lead potentially to conventional straddling stocks problems. On the other hand, small island countries are a tiny piece of shelf in the middle of an immense oceanic ecosystem and a large part of their resources are oceanic and straddle between the EEZ and the high seas.
The orange roughy (Hoplostethus atlanticus) is found on the deep slope areas off most oceans but direct fisheries have only developed in Australia and New Zealand. This species may reach 100 years of age and matures at an age of 20–25 years. Because of this and the associated slow growth, maximum sustainable harvest rates are of 1–5% of the virgin biomass. Present harvest rates are higher than this in most areas leading to unsustainable fisheries. The fishery started in the early 1980s in New Zealand and spread in Australia since 1986. Fishermen target large spawning concentrations in very localized areas. Because of the fish spawners' schooling behaviour locally high catch rates may hide overall stock decreases until stock collapse is close. A particularity of this species is that, because of its age at maturity and lifespan, effects of excessive fishing pressure will affect recruitment to the stock even 20–25 years later. Stock depletion of the species seems obvious but catches have continued to increase as new grounds were discovered. The extension of the New Zealand Challenger Plateau beyond 200 miles creates a straddling stock (Map 12). The species is exploited by Australia, Japan, Russia, Republic of Korea and Norway. Biomass and catch-rates decreased rapidly in recent years (Meltzer, 1992) and it is estimated that the current biomass is 20% of the pristine biomass. This indicates overfishing well beyond the level corresponding to MSY and, over the last two years, the TAC has had to be reduced from 12 000 to 1 900 t while New Zealand attempts to find ways of controlling foreign fishing outside the area under its jurisdiction.
Because of the low turn-over in such fisheries, there may be a temptation to exploit them through “pulse fishing”18 for economic reasons. Very cautious management practices are required if conservation and stable output from this type of resource are to be ensured.
18 Rapid depletion of resources in a short time followed by no fishing for a longer time to allow stock rebuilding
Although catches on spawning concentrations of orange roughy are virtually free of by-catch, at least one group of species is taken significantly in this fishery, the oreo dories (Allocyttus verrucosus, A. niger, Neocyttus rhomboidalis, Pseudocyttus maculatus) of which about 20 000 t are taken by Australia and New Zealand. Until recently, these species were discarded but over the past few years, fishermen have started to keep them and even to target at them. They reach depths beyond 1 000 m and may represent another straddling stock of unknown importance in the area.
The straddling oceanic resources of small island countries of the area consist essentially of tuna and tuna-like species (e.g. the narrow-barred Spanish mackerel Scomberomorus commerson), oceanic squids and sharks, flying fish and dolphinfish already addressed above. Although not treated in this paper, it is worth mentioning that small cetaceans also represent a potential straddling resource. The relative importance of oceanic resources for the island economy implies that regional management system19 covering the entire range of distribution of the resources should be put in place to ensure long term sustainability.
Map 12: The Challenger Plateau in the Southwest Pacific
19 A system ensuring the control of the overall fishing mortality applied to the stock, either in terms of TACs at fleet size, and providing for a forum where national allocations can be negotiated
A significant and hardly exploited stock of another Ommastrephidae, the jumbo flying squid (Dosidicus gigas) exists in the Southeastern Pacific Ocean, from California to the southern tip of Latin America (Map 9). The stock, which has yielded up to 19 000 t seems to be largely underexploited and is presently targeted inside the EEZs of Mexico (Gulf of California) and Peru as well as outside the Peruvian EEZ.
The Chilean jack mackerel (Trachurus picturatus murphyi) spawns across the ocean from New Zealand to Chile and seems to be able to complete its entire life cycle in the South Pacific Convergence, independent of the neritic zone (Bayley, 1989). The stock structure and potential subdivision into sub-species are still being argued (Parrish, 1989). On the Latin American coast, the species is found essentially off Peru and Chile between 1°30'N and 58°S and can extend its distribution further north during a period of anomalous climatic conditions (El Niño). Its distribution may extend as far as 900 miles offshore according to larval distribution, covering an area of 1.7 million km2 (Mathisen and Tsukayama, 1986).
Over the last two decades this species has provided one of the largest increases in world fish catch, from about 170 000 t in 1970–74 to 3.8 million t in 1990. The fishery developed off Chile and Peru after the anchoveta collapse, favoured by an increase of the area covered by the stock and its biomass (Tsukayama and Santander, 1987). At the end of the 1970s, the ex-USSR was looking for new grounds out of EEZs and a fishery yielding 500 000–6000 000 t/year was developed, first along and outside the EEZs of Peru and Chile. After 1985 the fishery extended westward along the west wind drift between 39° and 45° South and as far offshore as 80– 120° West and possibly beyond with seasonal shifts following the oscillation of the South Pacific subtropical convergence (Parrish, 1989), and catches of the ex-USSR fleet increased to 1.1 million t in 1989 and 1990. There is also an active fishery by Chile and Peru.
Total mortality of T. picturatus murphyi, estimated from catch curves in Peru and Chile, ranges from 0.57 to 0.90, a fairly high value for such long-lived animals (10–15 years). In 1983, exploitation rates calculated from the ratio between catches and acoustic biomass (8.9 million t) in the EEZ of Peru and Chile were around 16–25%, indicating that the resource was heavily exploited (at least locally). However, such values must be considered with caution as the data used did not cover the whole resource and all the removals (Mathisen and Tsukayama, 1986). The status of the whole stock of the South Pacific is not known.
The straddling stocks considered here are those which straddle over the EEZ limits of Canada, Greenland and EEC and stocks exclusively fished by coastal States but which extend beyond the 200 mile limits into international waters. These stocks are assessed by NAFO (the Northwest Atlantic Fisheries Organization), of which all coastal States except the USA, and a high proportion of DWFNs fishing outside of 200 miles of the coastline, are members. Most of the important fisheries are demersal, and to a significant extent, aim principally at cod, with a by-catch of a mixture of other bottom fish.
Most demersal stocks in this area are under coastal countries' jurisdiction except for two small areas, the “nose” and the “tail” of the Grand Banks which extend beyond the 200—mile limit and the Flemish Cap area (Map 13). Species occurring on this straddling shelf include the Grand Banks cod (Gadus morhua), American plaice (Hippoglossoides platessoides), redfish (Sebastes marinus), witch flounder (Glyptocephalus cynoglossus), Atlantic halibut (Hippoglossus hippoglossus) Greenland halibut (Reinhardtius hippoglossoides), yellowtail flounder (Pleuronectes ferruginaeus) and grenadiers (Macrouridae). Other straddling resources in the area include mackerel (Scomber scombrus) and neritic squids (Loligo pealei and Illex illecebrosus).
Map 13: The “Tail” and “Nose” of the Grand Banks (Northwest Atlantic)
The coastal States in the Northwest Atlantic sharply curtailed or eliminated distant-water effort in their EEZs in the 1970s, and with the exception of stocks on the tip of the Grand Banks and the Flemish Cap, and those for which advice has been requested by coastal States, management of shelf areas seaward of 200 miles has been conducted under the auspices of NAFO. This organization has attempted to maintain stock levels, or follow a stock-rebuilding strategy by harvesting depleted stocks at below the level providing the Maximum Sustainable Yield (fMSY). It is probably correct to say that all straddling stocks of groundfish in this zone are fished at or beyond the fMSY level, and that NAFO recognizes that “the groundfish stocks…. are now, generally, in the worse condition they have ever been”. Restrictive quotas have been placed on cod, American plaice, redfish and other groundfish stocks which are severely depleted (NAFO, 1992).
The causes of the recent sharp decline in cod resources of the Grand Banks to a record low biomass seem to be found in a combination of climate-related fluctuations of recruitment, increase in predation of young cod by growing populations of harp seals, decline of one major food item of the cod (the capelin), disagreement on management targets between countries participating in the fishery, inaccurate declaration of landings and fishing by non-member countries of NAFO and resulting uncertainty in the scientific forecasts.
The production in the northern areas of the Northwest Atlantic is influenced by the environment. The effect on cod has already been mentioned. There is also evidence that changes in ambient temperature, and not overfishing, are responsible for stock declines of American plaice. It is known that abundance and catches of mackerel and squid are generally higher in northern areas during warming trends in marine environments, which affects the sharing patterns for these stocks, not only between adjacent coastal States but between them and high seas fisheries.
The decline in straddling groundfish stocks of the Flemish Cap and nose and tail of the Grand Banks, has raised a number of controversial political issues regarding the reinforcement of the efficiency of international fisheries commissions, and the clarification of the interests of coastal States in regulating fisheries on those portions of straddling stocks lying beyond their EEZ's. Although the areas falling outside the Canadian 200—mile zone are relatively small, a much more significant part of the stock, through migration, may occur in these areas at certain periods of the year. This case also illustrates the difficulties faced by commissions not having independent means to control biases in statistical reporting and surveillance by participating countries, particularly when such reporting has direct implications on the quotas allocated in the following year. The inertia of the quota allocation mechanism is clearly evident, particularly in a period when declining abundance was not unambiguously reflected in all of the assessments. The consequences of the stock decline on coastal communities which became evident in 1992, has been the closure of domestic fisheries by the Canadian Government, followed by a compensation package to support fishermen in a province where unemployment is high, and job alternatives few.
A brief summary of the present status of stocks is given below:
Cod. Total catches from this the formerly very large Northwest Atlantic cod stock increased rapidly after 1959 as spawning and prespawning concentrations were heavily exploited by distant—water fleets, with peak catches of 800 000 t in 1968, with a steady decline thereafter to 1978. Inshore catches also declined from 160 000 t to 35 000 t in 1974. In 1992 the Canadian domestic cod fishery was suspended because of the disastrous state of this stock, and apparently voluntary restraint has been shown by some countries fishing outside 200 miles. Recent studies of North Atlantic cod have shown that stock abundance and distribution varies with climatic conditions: cod were rarer in the northern part of their range during “the little ice age” in the eleventh to thirteenth centuries: on the contrary, intermingling of stocks from Iceland to Northeast Canada, although not extensive, means that these stocks are not genetically isolated. This may have implications for long-term sharing arrangements.
Redfish. A long-lived species occurring on the shelf and slope of the Northwest Atlantic, this slow-growing species has shown poor resistance to unrestrained fishing. Most stocks were heavily depleted under the international fisheries that preceded extended jurisdiction, and have only slowly recovered for those stocks (within EEZs) where a long-term stock rebuilding policy has been followed. Straddling stocks are depleted and in need of stock rebuilding.
Flatfish. The American plaice, occurs on the Grand Banks, and is largely taken with haddock in the mixed trawl fishery aimed at cod. In recent years, northern haddock stocks in the West Atlantic have been low in abundance. In part, this is due (as for the flatfish) to high vulnerability to fishing, and slow growth and small size. There has been a significant discard rate of small flatfish in trawl catches in the Grand Banks area. Other flatfish such as the Atlantic halibut are currently relatively uncommon, and not object of a directed fishery. They occur in somewhat warmer waters than the Greenland halibut, a deep, coldwater species subject to directed fisheries in recent years.
A number of deepwater species occur in slope areas around the North Atlantic, and are taken by specialized trawlers. The only species currently of importance are grenadiers (Macrouridae).
Capelin. A small pelagic fish spawning inshore, recorded from the Grand Banks, where it plays an important role in the diet of cod and marine mammals. Acoustic surveys play a large part in assessment of these and other pelagic stocks, given that, as for other small schooling pelagics, the commercial catch rate is not a good indication of stock size. This species is not an important straddling stock but it is mentioned here because recent scientific advice has cautioned against heavy catches being taken from close to inshore spawning areas because of the effect this might have on future spawning and on the cod populations feeding on these stocks. This illustrates the link between management of straddling predator stocks and more national prey stocks.
Mackerel. Northwest Atlantic stocks of Scomber scombrus are managed as a single unit despite the existence of two spawning areas in the Gulf of St. Lawrence and between Cape Cod and Cape Hatteras; both groups overwinter in the Gulf of Maine and waters further south, and part of the stock may pass outside the 200-mile zone during migration. They were formerly subject to an intensive fishery by non-coastal States, which harvested a peak 430 000 t in 1973. This fishery was halted in 1977–78 with extension of jurisdiction of the USA and Canada and most catches are now taken inside EEZ's.
Squids. Neritic squids are accessible to fisheries on deep shelves and slopes and, as such, are potential candidates for straddling resources. The long-fin squid Loligo pealei spawns in inshore waters, depositing eggs on the bottom in shelf areas and then migrates offshore to overwinter. Its abundance measured by research vessel surveys during 1968–87 reached its lowest values in the late 1970s. Most catches are obtained in the EEZs and its contribution to straddling stocks in the area seem minimal. The short-fin squid (Illex illecebrosus) spawns in deep waters at the edge of the shelf where it may be vulnerable to high seas fishing and then moves northwards to enter shelf waters to feed. Stock size appears to be related to climatic factors at least as much as to fishing, and these factors may also influence both north-south migrations (which are often extensive) and inshore-offshore movements. A peak in Illex catches was reached in the late 1970s (90 000–180 000 t), catches have decreased significantly since then (5 000–20 000 t in the 1980s) and the stock is at least fully exploited.
The area is covered by ICES for research and management advice and the mandate for management lies with NEAFC and EEC. There are only three limited areas of high seas in the Northeast Atlantic: a small one over the deep shelf of the Barents Sea and two further south in deeper oceanic waters of the Norwegian Sea and the North Atlantic (Map 14).
The blue whiting (Micromesistius poutassou) is one of the main straddling resources. It is distributed throughout many EEZs and high seas zones during its life cycle, spawning in spring at the edge of the shelf west of Britain and Ireland, moving northwards between Norway and Iceland, to feeding grounds, where they overwinter. The fishery became fully established in 1977 and landings peaked in 1979–80 at more than 1 million t. Catches have decreased since then to 356 000 t in 1991. The stock was heavily overfished in the late 1980s. Since 1986, fishing mortality has decreased and is now close to natural mortality. The stock is increasing and is considered within safe biological limits.
The oceanic redfish21 (Sebastes mentella) is also an important straddling resource. The oceanic redfish exists essentially in the high seas area but straddles in the EEZ of Iceland and Greenland. The fishery started in 1982 on a virgin stock and the landings increased from 60 000 t in 1982 to 105 000 t in 1986 to drop subsequently to 38 000 t in 1989 and 23 000 t in 1991. The reason for the decrease is not ascertained. The biomass may be around 800 000 t and there is no scientific assessment on the present status of the stock.
Straddling demersal stocks of cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and Greenland halibut (Reinhardtius hippoglossoides) together with redfish exist in the Barents Sea but catches are believed by scientists to be insignificant despite press reports of intensive fishing.
20 Information taken from ICES, 1992
21 It is worth nothing that it is considered that there exist two different stocks of Sebastes mentella, the deepsea redfish, in EEZs, and the oceanic redfish in the high seas
Pelagic straddling stocks include the Norwegian spring-spawning herring (Clupea harengus). This species traditionally spawned on the west coast of Norway, fed in summer northeast of Ireland and overwintered east of Ireland and north of the Faeroes. This pattern seems to have changed in the late 1960s and the species is now distributed in the Norwegian zone most of the year. The stock is recovering from a historical collapse. It is increasing progressively due to good recruitment. The present biomass is still below the minimum biologically safe level of 2.5 million t and the stock is dominated by a single year class (1983). Catches and fishing mortality will be kept low until higher biomass builds up.
Separate statistics for EEZ and high seas catches are available for these stocks even though the reliability of the high seas data is uncertain and these stocks are assessed by ICES working groups as management units, taking into account data submitted on the whole stock range.
Map 14: The high seas areas in the Northeast Atlantic
The Mediterranean coastal countries have not extended their EEZs to 200 miles and most of them still have a 12-mile limit. The Mediterranean shelves are usually very narrow and there are therefore very few demersal straddling stocks. Two areas, however, have created straddling stocks problems: the Gulf of Lions and the Gulf of Gabes. In these two areas, the shelf extend beyond the 12-mile limit and its resources are, therefore accessible to others (e.g., Spanish fishermen in the Gulf of Lions and Italian and Greek fishermen in the Gulf of Gabes). The resources correspond to deep shelf and slope fish assemblages with hake and deep sea shrimps as the main target species. The General Fisheries Council for the Mediterranean (GFCM) has the capacity to address the problem in its entirety and has done so for the Gulf of Lions.
Straddling resources of small pelagic fish exist such as sardines in the Sea of Alboran, horse mackerel in the Central Mediterranean and, most probably, everywhere beyond 12 miles.
The continental shelf off this area is fairly narrow and most catches are taken inside the 200 miles, including small pelagic species such as sardine, mackerel and horse mackerel. Apart from tunas and tuna-like species and, possibly, oceanic sharks, only one species of fish, the blue horse mackerel (Trachurus picturatus) is known to migrate between the coast of Sahara and the offshore seamounts possibly reaching the Cape Verde Islands. This potential pelagic straddling stock is exploited by Eastern Europe fleets and by coastal countries, but catches are not distinguished from the other more neritic species of horse mackerel (T. trachurus and T. trecae). Nothing is known of its potential and status.
In the Lesser Antilles, the species which occur in and out of the EEZs and migrate through the archipelago are the flying fish (Hirundicthys affinis and Cypselurus cyanopterus) and the dolphinfish (Coryphaena spp.), the wahou (Acantocybium spp.), the blackfin (Thunnus atlanticus), yellowfin (T. albacares), albacore (T. alalunga) and skipjack (Katsuwonus pelamis) tunas, the Atlantic sailfish (Istiophorus atlanticus), the white marlin (Tetrapturus albidus) and blue marlin (Makaira nigricans), the king mackerel (Scomberomorus cavalla) and the oceanic sharks (Prionace glauca, Carcharhinus longimanus and Isurus oxyrinchus) (Mahon, 1987).
According to Joseph (1987), migratory species of the Caribbean region were the target of Japanese fisheries in the late 1950s and in the 1960s and the eastern Caribbean States witnessed the depletion of these stocks (referring to tuna and large tuna-like species) without sharing any of the benefits. The Republic of Korea, Taiwan (Province of China) and Venezuela joined in the '70s and dominated the fishery in the '80s.
The situation is similar to that described for the South Pacific and the establishment of EEZs has improved the control of coastal States on access to the resources but the problem of overall management and resources allocation remains. A good compilation of migration patterns of pelagic resources from this region is available in Mahon (1987).
Important straddling stocks, occurring both within the areas under national jurisdiction and in the adjacent high seas, can be found in the Southwest Atlantic. This is one of the few areas of the world where the continental shelf and slope extend well beyond the 200-mile limit, and therefore the main straddling stocks in this area are predominantly demersal. There is very little information on the offshore distribution of neritic pelagic fish stocks in this area. They are far less abundant and, excluding highly migratory species, there are no records of noticeable offshore catches of these species in the area.
In the southern part of FAO Statistical Area 41, between 41°50'S and 48°00'S, the Patagonian Shelf and Slope has a total area of about 12 323 mi2 extending beyond the 200-mile limit (Map 15). In this area, many important demersal fish stocks occur both in jurisdictional waters and adjacent high seas and are examined below.
Map 15: The Patagonian Shelf in the Southwest Atlantic
A large proportion of the total stock of the short-fin squid (Illex argentinus) occurs in the area over the Patagonian Shelf and Slope beyond the 200-mile limit. It is estimated that from 11–35% of the total biomass of this stock is concentrated in this area, which is also a main fishing ground for this species. The common squid (Loligo spp.) is also found both within and beyond the 200-mile limit. In the past between 2% and 12% of the total biomass of common squids has been reported in the area beyond the 200-mile limit. Total catches of these two groups of species increased consistently from around 100 000 t/year in the early 1980s to 744 000 and 750 000 t in 1987 and 1989, to then drop to 550 000 t in 1990. There are no current estimates of the proportion taken beyond the 200-mile limit, but in the past (1981) up to 74% of the total catches of short-fin squid were reported as taken in the area beyond the 200 miles. These stocks are mostly exploited by long-range fleets from the Republic of Korea, ex-USSR, Japan, Taiwan (Prov. of China), and Spain. Both the short-fin squid and the common squid stocks are considered to be fully- to over-exploited in the Patagonian Shelf area. A flying squid (Martialia hyadesi of the Ommastrephidae family) seem to be also presently exploited on the Patagonian shelf and surrounding waters but no detailed information is available. Further information on the distribution, abundance and exploitation of these stocks is provided in Otero et al. (1982), FAO (1983) and Csirke (1987).
The hakes (Merluccius hubbsi and M. polylepis) are the most important demersal fish stocks in the Southwest Atlantic. The Argentinean hake (M. hubbsi) has a more coastal distribution and is most abundant, and can rarely be found beyond the 200-mile limit. The Patagonian hake (M. polylepis) is less abundant and is found in the Patagonian slope and outer continental shelf, particularly around the Falkland Islands (Malvinas). Due to the overlap in their areas of distribution and the difficulty in distinguishing the two species through simple inspection, both the Patagonian hake and the common hake when caught offshore are usually reported under a single general category as hakes (Merluccius spp.). It is most likely that the Patagonian hake is the one that predominates in catches in the outer shelf and slope beyond the 200 miles. Several surveys conducted in the past suggest that around 2–6% of the estimated total biomass of these two stocks occurs over the shelf and slope beyond the 200 miles where they are reported in the catches of long-range fleets. These two stocks yield an annual total catch of around 425 000 t/year. They are mainly exploited by Argentinean and Uruguayan fleets that mostly operate inshore, off the River Plate basin and in the northern Patagonian shelf area, and by Spanish and Japanese long-range fleets that operate offshore further south, around the Falkland Islands (Malvinas) and on the outer Patagonian shelf. These stocks are considered to be fully exploited and, in view of their distribution pattern, it is unlikely that fishing operations beyond the 200-mile limit may have a noticeable impact in the overall abundance and total catches for these species.
The southern blue whiting (Micromesistius australis) is mainly distributed on the continental shelf and slope to the south of 38°S, including the Burdwood Bank. It is estimated that from 1–12% of the total biomass of the stock occurs in the area of the Patagonian Slope and Shelf beyond 200 miles, where it is exploited by long-range fleets. In 1990, the total catch of this species was 194 000 t, mostly taken by long-range fleets from Poland, ex-USSR, and Japan. There are no current estimates of the proportion taken beyond the 200-mile limit, but in the past (1981) up to 70% of the total catches of this species were taken in the area beyond 200 miles. This stock is considered to be under- to moderately-exploited.
The grenadier (Macrourus spp.) is also distributed in the southern Patagonian Shelf and Slope with 11–58% of its total biomass being reported to occur in the area beyond 200 miles. This stock has been yielding total annual catches of 20 000 to 50 000 t/year, mostly taken on the outer Patagonian Shelf and Slope by long-range fleets from the ex-USSR. There is no information on the proportion taken beyond 200 miles in recent years. The stock is considered to be moderately exploited.
Other demersal fish stocks are reported to straddle beyond the 200-mile limit: the pink cusk eel (Genypterus blacodes), the Patagonian toothfish (Dissostichus eleginoides), the tadpole mora (Salilota australis), the Patagonian grenadier (Macruronus magellanicus), the grenadier (Macrourus whitsoni), the Antarctic cod (Notothenia rossii), rockcods (Notothenia spp.), sharks and rays and common squid (Loligo spp.). It is estimated that about 1–16% of their biomass is outside the EEZ limit. These stocks yield 20 000–50 000 t/year and are exploited by Argentinean fleets and long-range fleets from ex-USSR and Poland. There is no information on the proportion taken outside the EEZ in recent years. Overall, these stocks are considered moderately exploited.
The shelf of this part of Africa is narrow and all reported catches are from the EEZs. No straddling stock conflict is reported. It is unlikely that large demersal straddling resources could occur in this region but the possibility exists for large and small pelagics. A likely candidate for straddling resources is the horse mackerel. Although no oceanic horse mackerel has been described for this area, Wysokinski (1986) notes that Trachurus trachurus is found in concentrations on the shelf but also over depths up to 3 500 m. Landings of this species reached more than 600 000 t in the early 1980s but catches were reported essentially from inside 200 miles. Other candidates might be the pomfret (Brama spp.), which yielded catches of about 1 000–4 000 t, and the myctophids (as Lampanyctodes hectoris) which has yielded catches of 40 000 t in 1973. The possible existence of significant straddling stocks in this area is therefore purely speculative and these stocks would, in any case, represent a very small proportion of the landings and economic value of the fisheries of the region.