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The Canary Current:; Studies Of; an Upwelling System

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The Canary Current:; Studies Of; an Upwelling System Rapp. P.-v. Réun. Cons. int. Explor. Mer, 180: 432-446. 1982. Distribution and abundance of demersal resources of the CINECA region Jeronimo Bravo de-Laguna Instituto Espanol de Oceanografia, Laboratorio de Canarias Av. José Antonio 3, S/C Tenerife, Espana The demersal resources of highest commercial value in the CINECA region are the hakes, sea breams, sciaenids, cephalopods, and crustaceans. They are distributed on the continental shelf and slope, down to 500 m depth, between the Strait of Gibral­ tar and Cape Verde. This paper gives a summary of the current knowledge on the distribution and abundance, in the different zones, of 26 fish species, 3 cephalopods, and 9 crustaceans. Les ressources démersales les plus intéressantes du point de vue commercial dans la région CINECA sont les merlus, les sparidés, les scienidés, céphalopodes et crusta­ cés. Leur distribution s’étend sur la plateforme continentale et le talus jusqu’à une profondeur de 500 m entre le Détroit de Gibraltar et le Cap Vert. Le présent travail comprend un résumé des connaissances actuelles sur la distribution et l’abondance, dans les differentes zones, de 26 espèces de poissons, 3 de céphalopodes et 9 de crustacés. Introduction The continental shelf of West Africa, between the demersal species of the CINECA region is presented. Strait of Gibraltar and Cape Verde, is one of the main These are the hakes (3 species), the sea breams (21 fishing zones of the world. The special hydrological species), the sciaenids (2 species), the cephalopods (3 conditions caused by the Canary Current and upwelling species) and the crustaceans (9 species). provide good feeding conditions for a large number of pelagic and demersal species. Their economic import­ ance has attracted the interest of fishing fleets from coastal countries of the region and from several Euro­ Hakes pean and Asiatic countries. The fishing activity has not been followed up suffi­ In the CINECA area the following species exist: Mer- ciently by research on the distribution and biology of luccius merluccius, Merluccius senegalensis, and Mer- the most important commercial species and assess­ luccius cadenati. The biology and distribution of these ments of the state of exploitation of these species. species have been studied extensively (Maurin, 1954; While information about the physical, chemical, and Collignon, 1969, 1971; and Domanevsky and Stiop- biological characteristics of the environment has kina, 1973). There are, however, no good data on increased greatly since the CINECA programme, there catch, fishing effort, or fishing areas. Evaluations on is still a significant lack of good data on fishing effort, stock abundance have been done by using data from fishing areas, and catch with a correct break-down by quantitative trawling surveys only (Collignon, 1969; species. Domanevsky and Stiopkina, 1973; Domain, 1974). For these reasons, the CECAF Working Party on Along the coasts of Mauritania, between 75 and 250 Resources Evaluation has not been able to arrive at metres depth, the hakes are estimated to constitute clear conclusions about the state of the resources. 35 % of the total fish biomass. Actually many of the most important commercial Figure 282 shows the vertical and geographical dis­ species seem overfished. An example is the sea bream tributions of the three species. Merluccius merluccius fishery which has been replaced by the cephalopod are distributed from the Strait of Gibraltar to Senegal, fishery. This phenomenon will be discussed later on. but are uncommon south of Cape Bojador and disap­ In the present paper, the available information on pear completely south of Cape Blanc. The juveniles are the distribution and abundance of the most important mainly found in shallow waters on the continental 432 A ..36* STRAIT OF GIBRALTAR . 3 5 * 34*~ • RABAT 33* oos oos - 32*o o . SAFI ESSAOUIRA 0 31 * 2 00 2 1 AGADIR 30* CO SIDI IFNI 29° ■ . 28 # CABO JUBY 009 009 - 2 7* .2 6* CABO BOJADOR o o m . 25* CABO LEVEN VILLA CISNEROS 50 50 - 80C 23* 150 150 - 750 22* CABO BARBAS J 1 CABO BLANCO 20* _ CAP TIMIRIS 19“ o 0 CO 18“ 1 NOUAKCHOTT 300 S 17* 150 150 - 16* ST. LOUIS 15 CAP VERDE ■ A 14* “N A Merluccius merluccius 0-750 m % Merluccius senegalensis 35 -8 0 Om 1 Merluccius cadenati 150- 600m Figure 282. Vertical and geographical distribution of the three Merluccius species. shelf, while the adults occur closer to the continental mainly found at depths of 150-400 m between Villa slope. During the spawning season, the adults move Cisneros and Cape Juby (Domanevsky and Stiopkina, farther inshore, and afterwards out to deeper waters. 1973). North of Cape Juby, the adults occur mainly North of Cape Juby, juveniles less than 30 cm total between 100 and 500 m depth, and fish larger than 40 length are most abundant between 0 and 150 m depth, cm are usually found deeper than 300 m. Between Villa and the main abundance is generally found deeper than Cisneros and Cape Blanc the hake is found between 50 m. South of Cape Bojador young hakes are rarely 300 and 750 m. found on the shelf and they do not occur in the by-catch Poinsard and Villegas (1975), using data on the fish­ of the cephalopod fishery. Juveniles (8-22 cm t.l.) are ing activity of the Moroccan fleet, have made an assess- 28 Rapports et Procès-Verbaux 433 36 * STRAIT OF GIBRALTAR 3 5* 34 * 33 * SAFI 3 2 * ESSAOUIRA 31* AGADIR 30 * SIDI IFNI 29 * 28 * CABO JUBY 27 * 26 * CABO BOJADOR 25 * CABO LEVEN 2 4* VILLA CISNEROS 23 * 22* CABO BARBAS 21* CABO BLANCO 2 0 * CAP TIMIRIS 19- 18* NOUAKCHOTT . 17* 16* ST. LOUIS . 15* CAP VERDE . 14* •N A Dentex macrophthalmus 25-500 m ■ Puntazzo puntazzo 10 - 6 5 n a Dentex maroccanus 30 - 500 m ▼ Boops boops 0 - 200 m ODiplodus cervinus 80 -100m • Diplodus sargus 0 - 50 m □ Diplodus vulgaris 0 ~ 5 0 m Figure 283. Vertical and geographical distribution of sparid species. ment of the hake. Along the coast of Morocco, the assessment using data from 230 trawl stations at 20-500 fishing effort is mainly concentrated on the younger m depth, between 35°N and 20°N. They estimated the part of the stock, age groups 0 to V, found in shallow total biomass of Merluccius merluccius to be about waters between 50 til 150 m depth. The calculated 50000 t, of which 80 % were juveniles. MS Y for this part of the stock is 3300 tonnes/year. This Merluccius senegalensis is an African species distri­ figure is probably an underestimate due to lack of data buted from the southern coast of Morocco to Guinea, from other fleets fishing on the older part of the stock with the highest abundance between 20°N and 13°N in the same area. (Fig. 282). Maurin (1954) has described the biology of Domanevsky and Stiopkina (1973) have made an this species along the coast of Morocco. The vertical 434 distribution of M. senegalensis changes according to the in the yields of sea breams has been observed, (Garcia seasons of the year. In winter the young hakes are Cabrera, 1968, 1969, 1970; Bas et al., 1970). found near the coast in shallower waters than M. mer­ The horizontal distribution of sea breams is rela­ luccius. At depths between 35 and 75 m about two tively uniform, but the largest concentrations occur thirds of the stock of M. senegalensis have a total length south of Cape Juby. In the cephalopod fishery, which less than 25 cm. Below 100 m fish larger than 50 cm takes place south of Cape Garnet, the sea breams con­ constitute 90 % of the commercial catches. In the sum­ stitute the most important part of fish discard: 23 % of mer when spawning takes place, M. senegalensis the total catch in shallow waters off Villa Cisneros and migrate to deeper waters, and the main concentrations about 5 % off Cape Barbas, (Bravo de-Laguna et al., are found between 80 and 120 m. In general, M. 1977a). Between Cape Corveiro and Cape Blanc the senegalensis spawn in shallower waters than M. merluc­ sea breams are especially abundant and constitute cius. During winter, fish smaller than 30 cm are usually about 60-70 % of the commercial catches. Practically found above 40 m, while larger fish constitute 80-90 % all the species of sea breams in the CINECA region are of the catches from depths below 100 m. found in this area. South of Cape Blanc, at depths From Cape Juby to Cape Blanc M. senegalensis are down to 40 m, the sea breams represent 18 % of the regularly caught on the slope and at the edge of the demersal fish population, and from 75 down to 250 m, continental shelf between 100 and 800 m depth. North Dentex spp. only represent 43 % of the total available of Cape Bojador, juveniles are mostly found on the fish biomass. shelf at depths less than 80 m. Farther south this Bonnet (1969) distinguishes between three groups of species occurs mainly at depths of 100-400 m, but it is sea breams according to their geographical distribu­ rarely caught as by-catch in the cephalopod fishery. tion. The first one is composed of those species that Near Cape Blanc, the largest concentrations occur at occur throughout the area and whose geographical depths of about 200 m and between Cape Blanc and limits extend beyond it. A typical example of this Cape Timiris M. senegalensis is the most abundant category is Dentex macrophthalmus. The second cate­ species on the continental slope. Farther south its gory comprises septentrional species, for which the abundance decreases and it is replaced by M.
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