Full Length Research Paper
FV Oluwale, Adiaha, AA Ugwumba
Abstract
Sizes at maturity (Lm50), fecundity, sex ratio and gonado somatic indices for Papyrocranus afer, collected from Lekki Lagoon, were studied from January 2010 to April 2012. In total 1154 specimens with standard lengths, 5.2-75.9 cm (34.86±17.2cm) and body weight, 7.9-1, 958.8g (249.12 ± 28.56g) were collected by means of artisanal passive and active fishing gears (traps, long lines and nets. Sexes of fish specimen were determined macroscopically after dissection and the length at which 50% of the fish population reaches sexual maturity (Lm50) was considered as length at sexual maturity. Fecundity was determined by total counts of eggs; sex ratio by proportion of male to females, and gonadosomatic index (GSI) was expressed as gonad weight as percentage of total body weight. Results indicated that the most frequently caught fish size was 34.5cm; while sizes at maturity were 49.1cm (males) and 53.4cm (females).There was significant difference in estimated sex ratio X 2 (1) = 32.21, p < 0.0001, 1:0.6 (Male: Female). Fecundity was low (mean 49 ± 17 eggs for a fish 52.86 ± 7.53 cm); it increased with fish size (r = 0.71). Higher GSI during rainy season with peak in July (female: 0.44 ± 0.14; male 0.22 ± 0.01 %) indicated seasonal spawning. Low fecundity and annual spawning underlined the need for sustainable exploitation and management of this species in Lekki Lagoon.