Fishing gear selectivity on sub-adults and spawning stock of the Tarpon Megalops atlanticus (Actinopterygii: Megalopidae) in Northeast Brazil

Abstract

The Tarpon (Megalops atlanticus) is a species with economic importance as a food fish and a source of income for artisanal fishers. Research regarding the reproductive biology of this species is scarce or incomplete, especially for this species in northeastern Brazil. Tarpon were caught each month near the Bitupitá district using longline fishing and arrowhead fixed traps, from October 2017 to September 2018. The Tarpon specimens were weighed, measured, and the type of fishing equipment used for the capture was noted. Gonads were obtained and evaluated macroscopically, and fixed and preserved for future microscopic analyses. The present study observed 150 females and 102 males for a total of 252 individuals. The sex ratio was 1:1.5 (M:F) and females showed a dominance in the longer length classes. Both sexes presented negative allometry (b < 3). The gonadosomatic index (GSI), Fulton’s condition (K) values and sexual maturity indicate that the reproductive period occurs between August and November, which is during the dry season. The length at first maturity (L50) presented values of 101.7 cm total length (TL) for females, 99.4 cm TL for males and 101 cm TL for both sexes grouped together. The mean fecundity was 7.5 million oocytes and the species present asynchronous oocyte development, multiple spawning periods, and continuous recruitment of oocytes from the reserve stock indicating indeterminate fecundity.