Notes on the biology of the bigeye scad, Selar crumenophthalmus (Carangidae) around Reunion Island, southwest Indian Ocean

Abstract

The main characteristics of the biology of bigeye scad were studied from commercial fishery catches around Reunion Island. Biometric relationships were calculated. The monitoring of size distribution, aggregated by month, allowed us to estimate the theoretical growth equation using the ELEFAN software. The von Bertalanffy growth parameters were adjusted with a seasonal modulation: L∞ = 265 mm; K = 1.64 year; c = 0.068; = 0.38. The growth of the cohort was quite high during the austral summer (Novermber-April) and decreased during the austral winter (May-October). The arrival of a new cohort with homogeneous small sizes (65 to 90 mm) in the fishery in November coincided with the disappearance of large individuals. A feature of the reproductive biology was that the sex ratio remained constant month by month and that there was no predominance of male or female even in the larger size classes. Fish were mature by April and the proportion of mature fish progressively increased until November, when the gonad-indices were the highest. The size at first maturity (L50) was reached at 215 mm (fork length). The largest specimens-observed were 255 mm long (fork length). After reproduction, massive mortality occurred and few individuals survived.