The feeding regime of the Spanish mackerel (Scomber colias Gmelin, 1789) under ordeal by time: A change to the detriment of prey-species of the genus Sardinella

Abstract

Sardinellas are amongst the principal fishery resources of the Ivorian coastal areas, being the prey of predatory fishes, of which tunas. A close observation of the trophic ecology and fisheries data in the scientific literature permitted to gain insights into previously-held relationship between the Spanish mackerel and the Sardinellas regarding feeding. We recall past facts accounting for the disappearance of both species from the landings, following the scarceness of the round Sardinella (Sardinella aurita). This study was carried out to investigate the current relationship between both species, selecting a fishery for its heavy catches for Sardinellas. Samples of Scomber colias were taken each week of July and August from that fishery in 2022. A total of 115 specimens were collected at the landing stage of Sassandra (Southwestern Côte d’Ivoire). The fish were measured and weighed, and stages for sexual maturity of their gonads were estimated. The results indicated that specimens ranged in size from 20.4 to 35.5 cmFL while their stomachs measured between 1.8 and 9.6 cm. Stomach contents weights ranged from 0.05 to 36.5 g. The stomach contents analysis showed a feeding regime made up mainly of small organism-prey, of which the mantel shrimp Scyllarides herklotsii, the pink shrimp Farfantepenaeus notialis, the spiny lobster Nephropsis atlantica, juvenile fish species of the Myctophidae family, juvenile Cephalopods (squids), and almost no fish of the genus Sardinella. The occurrence of a large proportion of empty stomachs (whose weight was <2.0 g) was noticeable, since the Spanish mackerel mainly fed on small prey.