Search

WOS:000459212600005; International audience; The gross energy content of spawning batches and the microchemistry of sagittal otoliths in individual female bonga shad Ethmalosa fimbriata were compared between contrasting sampling sites at the Senegalese southern coast and inside the hypersaline Sine Saloum Estuary. Results show that females spawning in the estuary's middle reaches invested almost three times more energy into reproduction (115 ± 65 J g?1 body mass) than their neritic counterparts (39 ± 34 J g?1 body mass). Also, female otolith levels of Ba:Ca, Sr:Ca and Zn:Ca either differed significantly between study sites or could be linked to heterogeneous environmental variables. A quadratic discriminant function analysis provided evidence of segregated spawning populations of E. fimbriata in southern Senegalese waters.

A multiplex haplotype-specific polymerase chain reaction (MHS-PCR) method was developed, which identified seven Clupeiform species living in the tropical Eastern Atlantic region: Sardinella aurita, Sardinella maderensis, Ethmalosa fimbriata, Sardina pilchardus, Engraulis encrasicholus, Pellonula leonensis and Ilisha africana. 16S rRNA fragments were amplified using a species-specific set of primers, yielding species-specific size fragments, and then separated using agarose gel electrophoresis, enabling direct visual identification of targeted species. This method provides an accurate, easy and rapid tool for identifying species within large Clupeiform samples. It is suitable for investigations on early Clupeiform stages, species and identification in fishery management in the tropical Eastern Atlantic area.

The monthly feeding activity and food habits of populations of Ethmalosa fimbriata occurring in the sea and an estuary in Cape Coast, Ghana district were investigated during a 14-month period. The juvenile fish, whose total length (T.L.) ranged from 5.3 to 14.7 cm, occur in the estuary and appeared to be more active feeders than the marine samples which measured 15.0–30.4 cm. The peak feeding activity in the marine population coincided with the onset of‘upwelling’ in the sea, which period is characterized by high salinities, decreasing temperatures and high zooplankton production. The species is primarily a plankton feeder. The stomachs of the marine samples contained mainly protozoa, crustacea, molluscan larvae and a considerable amount of detritus while the stomachs of the estuarine fish contained mainly phytoplankton, protozoa, sand grains and organic detritus. These observations have been discussed in relation to other reports on populations occurring along the West African coast.

The gonads of Ethmalosa fimbriata have been classified according to five and four maturity stages in the male and female, respectively. The species appears to mature at 22.0 cm in Ghana waters. The fecundity and frequency distribution of oocytes have been determined. Monthly changes in the proportions of gonadal stages and gonadosomatic index indicate that the species spawns in the sea from October to March. The results have been compared with data on populations occurring in other West African countries.

The biology of the population of Ethmalosa fimbriata occurring in the Lagos lagoon was investigated. Three size groups, 35–69 mm (Yoyo), 70–169 mm (Efolo) and 170 mm and above (Agbodo) occur in the lagoon and the spatial distribution of these size groups and the length frequency distribution of the species is given. The relationship between length, weight, age and growth is discussed and the food and feeding intra-relationship of the size groups is shown. Information on the fecundity and possible spawning periods is discussed.