An Upwelling System
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Rapp. P.-v. Réun. Cons. int. Explor. Mer, 180: 405^122. 1982. Fisheries in the CINECA region M. Ansa-Emmim FAO/UNDP CECAF Project B. P. 154, Dakar, Senegal The CINECA region extending from Gibraltar to about 10°N latitude is one of the richest fishing grounds in the world. The occurrence of permanent upwelling gives rise to high primary productivity and hence rich fisheries resources. Until recently, fishing in the region has been conducted mostly from inshore canoes. The present fisheries are composed of local artisanal, semi-industrial and industrial fleets as well as fleets from Europe and Asia. Fish stocks found in the region range from large shoals of pelagic species such as sardines and sârdinellas, to mixed demersal species. Several stocks in the region have become heavily exploited, but their state of exploitation is difficult to assess owing to lack of good data. This paper describes the fisheries, the present state of exploitation of the various stocks, and their management. Introduction Fisheries resources The CINECA region extending from Gibraltar to 10°N In describing resources of this region, three types can latitude is one of the richest fishing grounds in the be distinguished: the demersal fishes (e.g. sea breams, world. This is due to the occurrence of permanent groupers); the coastal pelagic fishes (e.g. sardines, sar- upwelling which gives rise to high primary productivity dinella, and the mackerels); and the oceanic pelagic and hence rich fisheries resources. species (e.g. tunas, sailfishes). Figure 269 gives the Fishing operations by both local and foreign fleets general distribution of species groups in West Africa. have been carried out for a long time. Within a period This figure is fairly representative for the West African of about twelve years (1958-1970), total catches tropical fish fauna between 20°N and 15°S. reported for this region rose from around 400 000 ton nes to over two million tonnes. This rapid increase has been due to the activities of long-distance fleets of many countries from Asia and Europe. The present The pelagic resources fisheries still attract a large number of fishing vessels The most important pelagic resources in the region are from countries outside the region as well as an increas the sardines off Morocco and Mauritania, and the sar ing number of local vessels. dinellas, mackerels, and horse mackerels mainly distri Fish stocks found in the region range from pelagic buted from Mauritania to Sierra Leone. species such as sardines and sardinellas to mixed tropi Mgrations of the sardine (Sardina pilchardus) are cal demersal species. The type of fishing vessels ranges not well known, but there are theories based on the from artisanal canoes to the most sophisticated stern/ movements of the various fishing fleets in the area freezer trawlers and factory ships. Some stocks have (Belveze, 1972; Bravo de Laguna et al., 1976, 1977). already shown signs of overfishing; others are being The young sardines move northwards in spring and fished close to their maximum potential yield. generate seasonal fisheries off the Moroccan coast The multinational nature of the fisheries and the from May through July/August. The sardines migrate large variety of species and fishing gears complicate the southwards during the second half of the year, again implementation of any proper management policy. giving rise to fisheries off Agadir (Morocco). Management of these stocks is, however, the collec Sardinella aurita perform both seasonal migrations tive responsibility of the coastal states, and close col perpendicular to the coast and daily vertical move laboration among these states is required. ments depending on age, sexual condition, and hydro- graphic situation. More important for the fishery is the 405 m acker el Pomadaiydae Figure 269. Distribution by depth of species or species groups off the west coast of Africa between 20°N and 15°S. (Anon., 1971). seasonal migration parallel to the coast related to the Demersal resources movement of the boundary between the warm and cold waters in the areas of seasonal upwelling south of Cape The most important demersal resources are the sea Verde. Sardinella move closer to the coast for spawning breams, hakes, and cephalopods, (squids, cuttlefishes, in May/June along the coast of Senegal (Boely and and octopi). The distribution of demersal stocks in the Fréon, 1980) followed by a northern migration in July region is related to the bottom deposits. Fishes like the and August as the warm-water front progresses north flatfish (Cynoglossus canariensis), the polynemidae, wards. In winter it is likely that they return to the the rays, the sciaenidae, and the penaeid shrimps in south. habit the coastal muddy or sandy grounds. The ser- The mackerels have seasonal migrations parallel to ranidae, lutjanidae, most sparids, and cephalopods the coast similar to those of 5. aurita. Figures 270-274 inhabit the coastal hard bottoms. Hakes, some spari- give schematic representations of these migrations, dae (Dentex angolensis and Dentex macrophthalmus), according to Boely et al. (1979). Paracubiceps ledanoisi, Brotula barbata, and the deep Sardinella eba are more coastal and more euryhaline, sea shrimp (Parapenaeus longirostris) and the crab preferring warmer waters (above 24°C). The concen (Geryon quinquedens) are some of the important trations are found within the 30 m depth zone mainly species inhabiting the edge of the slope of the continen off Senegal, Guinea, and Sierra Leone. Other small tal shelf. pelagic fishes such as bonga (Ethmalosa fimbriata) are Contrary to pelagic resources which exhibit migra found in close inshore areas with low salinity waters tions related to the seasonal changes in the hydrologi (e.g. around The Gambia). Anchovy (Anchoa guineen- cal regime, migrations of the demersal resources are sis) also occur very extensively, but there is no large- relatively restricted. Some species, however, under scale fishery for this species. take seasonal movements perpendicular to the coast. It 406 MAY JUNE AUG SEP OCT DEC RIO PE PRO 23° 22- 20* MAURITANIA Nouakchott 1 6° SENEGAL GUINEA BISSAU li” Weak concentrations Mean concentrations Big concentrations >___ ». Route of adult sardinella Nursery ^ Main spawning —► Minor spawning Figure 270. Migratory cycle, spawning periods, nurseries, and monthly location of adult Sardinella aurita in the Senegalo- Mauritanian area. (After Boely et al., 1979). 407 RIO DE ORO RIO DE ORO 22° 21° • tø o uad h i bou Nouadhibou MAURITANIA MAURITANIA June Nouakchott Nouak c hotl 18° 16° 15“ SENEGAL 15° _ SENEGAL a kar U" G A-M-B i ' K GAMBIA 13' G U ' K< E A • GUINEA BISSAU 12„ * BISSAU V\• Important nurseries fc y ÿ l Important nurseries Observed distribution of fish with modal length more than 24 cm > ► Displacement of adults * * Observed displacements ^ Main spawning R : Reproduction Figure 271. Displacement, main period of reproduction, and Figure 272. Migratory cycle, spawning periods, nurseries, and nurseries of Sardinella maderensis in the Senegalo-Mauritani- location of principal adult concentrations of Caranx rhonchus an area. (After Boely et al., 1979). in the Senegalo-Mauritanian area. (After Boely et al., 1979). 408 RIO DE ORCf RIO DE ORO23* 22* 22* Nou adh ibou hfouadh ibou 20* „Vv MAURITANIA MAURITANIA Nouakchott Nouakchott i®* 17* 16* SENEGAL 15* SENEGAL .Dakar Dakar GUINEA BISSAU Important nurseries Displacement of adults ^ Main spawning Minor spawning Figure 273 (left): Trachurus trecae; Figure 274 (right): Trachurus trachurus. Migratory cycle, spawning season, and location of main adult concentrations of Trachurus trecae and Trachurus trachurus in the Senegalo - Mauritanian area. (After Boely et al., 1979). 409 is presumed that hake migrate seasonally into shal Table 83. Catches of the Senegalese artisanal fleet for 1975 lower waters as well as along the coast, but the range is and 1976 in tonnes not known. Fishes 1975 1976 Good fishing grounds for the pink shrimps (Penaeus Sardinella/anchovies 50 703 68 279 duorarum) are mainly found in the vicinity of large Ethmalosa fimbriata 21 410 18 755 lagoon entrances and river mouths at depth of 20-60 Epinephelus spp. 10 781 10 806 Dentex spp. 1 655 1 084 metres. Juveniles of this species are also caught in the Pagrus spp., Dentex spp. 18 185 16 221 lagoons and rivers during the seaward migrations. The Pomatomus saltatrix 9 662 10 951 following stocks have been identified in the area: the Pseudotolithus spp. 18 056 18 788 Cape Timiris, Saint Louis, and Roxo-Bissagos stocks. Caranx spp. 11 111 17 099 Trachurus spp. 9 842 8 300 These are separate stock units without any interrela Mullidae 15 187 14 091 tion between them (Anon., 1977a). Lutjanus spp. 1 320 1 691 Sphyraena spp. 5 818 4 251 Sharks 6 405 8 207 Oceanic resources Other fishes 83 814 66 349 The most important of the oceanic resources are the Crustacea tunas (especially yellowfin, skipjack and bigeye). Shrimps 1 734 1 146 Tunas abound fairly close to the continental shelf in the Lobsters 421 214 warmest waters of the region. The fishery for oceanic Crabs 131 112 Other crustacea 61 99 squids and myctophids, which may provide large potential resources, has not yet been developed. Mollusca Sepia sp., Loligo sp. 2 806 2 069 Cym bium sp. 6 256 6 840 Bivalves 659 771 The fisheries Oysters - 156 Other 38 69 Fisheries of the region can be conveniently classified into artisanal, local semi-industrial or industrial, and Total 278 433 276 258 long-distance fisheries mainly conducted by non-Afri can countries. Source: Ba, M’Baye (1976). Artisanal fisheries The total catches of the artisanal fishery in some The artisanal fishery is important in Senegal and The countries have significantly increased during the past Gambia. It is estimated that there are over 16 000 ten years. In Senegal, artisanal landings increased from canoes (Talarczak, 1976) in the northern sector of the 83 000 t in 1965 to 278 433 t in 1975.