Recruitment pattern and length-at-first-capture of the silvercatfish Chrysichthys nigrodigitatus Lacépède (1803): claroteidae in Lower Cross River, Southeast Nigeria

Abstract

The recruitment pattern and length-at-first-capture of Chrysichthys nigrodigitatus from lower Cross River, Nigeria, were derived from 12 consecutive month length - frequency samples (October 2011 to November 2012) using FAO – ICLARM Stock Assessment Tools (FiSAT II) software. Recruitment was continuous all year-around with two peaks of unequal pulses: the major in March-April (15.19-15.32%) and minor in July-August (11.10-13.16%), apparently occurring during rainy and early dry seasons, respectively. No recruitment was observed in October. The recruitment pattern observed was consistent with the general spawning pattern of the species (April - August) reported by earlier researchers. The probability of capture routine estimated the mean length-at-first-capture, L_c = 36.24 cm. The mean ratio of length-at-first-capture (L_c) to asymptotic (L_∞) was 0.309 indicating the length at-first-capture was quite low for the population indicating higher fishing pressure on the stock, thereby endangering the health status of the resource.

Keywords: Artisanal fishery, fishing season, logit transformation, resource sustainability, running average