4.1 Sardinella aurita
4.2 Sardinella maderensis (= S. eba)
4.3 Trachurus trachurus
4.4 Trachurus trecae
4.5 Caranx rhonchus
4.6 Scomber japonicus
4.7 Sardina pilchardus
According to the Atlant-NIRO studies for the southern sector, and of CRODT for the northern sector, two stocks have been identified, one between 10°N and 25°N, the other centered on Sierra Leone.
In the case of the first, there are two nurseries, one toward the Arguin Bank, the other south of Dakar. The adults move over the entire area of the stock range according to climatic conditions (Boëly et al., 1978 and Annex 4, Fig. 1).
The area covered by the second stock extends widely toward Liberia in the south and Guinea to the north.
According to the studies by CRODT there are two nurseries in the Senegal-Mauritanian zone. They coincide with those of S. aurita but, in the case of this species, large individuals are only caught north of the Cape Verde Peninsula. Little is known about the relationships between the nurseries themselves and between the nurseries and large specimens (Boëly et al., Annex 4, Fig. 2).
In the Sherbro Division there seems to be only one stock at the level of southern Guinea and Liberia.
Soviet studies define three populations: the first, north of 26°N, does not concern this working group; the second is situated between 19°N and 25°N, and the third between 14°N and 17°N. The areas of geographical distribution of the last two populations may overlap in the course of the year (Overko and Mylnikov, Annex 5, Fig. 1; Zenkine, Annex 6).
According to Soviet surveys, two independent populations may be identified in the zone under study; one around Sierra Leone, the other around Mauritania. For the northern population, the hypothesis of a division into two stocks at the level of the Arguin Bank has been proposed (Overko and Mylnikov, Annex 7, Fig. 1).
Some concentrations of T. trecae have been observed off the coast of Senegal, especially in the cold season (Domain, 1970; Boëly et al., 1973; Chabanne and Elwertowski, 1973).
Soviet researchers have identified three populations in the following zones: - 8°N to 11°N; -14°N to 17°N; -18°N to 20°N. Intermingling can occur between the last two populations.
Some of the participants were not convinced as to the identification of these populations and other hypotheses were put forward (Domain, 1976; Boëly et al., Annex 4, Fig. 3).
Soviet studies have made it possible to define two populations in the Senegal-Mauritanian zone, one at the level of the Sahara, the other, farther south off the coast of Mauritania and northern Senegal.
In the Sherbro division concentrations of mackerel are found which could belong to a population identified in the Gulf of Guinea.
According to information and studies presented by the USSR, CRODT and FAO, it would seem that the area of distribution of this species has descended toward the south in recent years. The southern limit of concentrations has gradually passed from 26°N in 1966 to 17°N in 1977 (Domanevsky and Barkova, Annex 8, Fig. 2), and the sporadic appearance of this species has been observed in Dakar in recent years (Fréon and Stequert, 1978).
