Reproduction aspects of Plagioscion magdalenae (Pisces: Sciaenidae) in El Guájaro reservoir, lower Magdalena, Colombia

Abstract

Plagioscion magdalenae is the most important fish resource of the El Guajaro reservoir, Colombia, and its riparian inhabitants, fundamental for subsistence fisheries in the region, which has led to its overexploitation. This paper describes and evaluates the reproductive aspects of P. magdalenae in this reservoir. Ten monthly collection samplings were made between April 2018 and January 2019, in order to cover each moment of the flood pulse. We calculated sex ratio, gonadosomatic ratio (RGS), fecundity, oocyte diameter and minimum and mean size at sexual maturity (L50). We analyzed 207 specimens and established seven size intervals; 126 individuals were males and 81 were females, with an overall sex ratio 1:1.6 (female-male). The RGS indicated that this fish has several reproductive peaks, the mam ones being in July and September. Absolute fecundity was 1909 oocytes for falling water, 1590 for low water, 2435 for rising water and 2132 for high water; with an average oocyte diameter of 0.29 mm. Males matured earlier than females and their mean size at sexual maturity was below the mean catch size (30 cm), reflecting that legal regulations are well stipulated, but there is no strict control for fishing.