Temporal Variation in Fish Species Abundance in Relation to Gear Selectivity, in Tagwai Lake, Minna, Nigeria

Abstract

The need for cost-effective fishing in in-land fresh water lakes informed this study, which assessed the abundance of fish species in relation to vulnerability to fishing gears in Tagwai Lake, Minna, Nigeria. Three types of gears namely, cast net, gill net and hook-and-line, were deployed in the lake during 16 consecutive weeks for collection of fish samples. The results indicated the presence of seven fish species, in order of decreasing relativeabundance: Tilapia zilli > Auchenoglanis occidentalis > Tilapia galilaea > Clarias gariepinus > Alestes lesciscus > Bagridae chrysichthys > Mormyrus rume. While, the Tilapia species and A. lesciscus were vulnerable to cast and Gill nets, M. rume was collected only by the former type of net gear. Likewise, the Cast net was the only gear sensitive to A. occidontalis, B. chrysichthys and C.gariepinus. The Cast net was by far the most productive gear, with six fish species and >90% of all specimens collected, while hook-and-line yielded no catch. The dominant species in cast netcollections was T. zilli (41.13%) while, that of Gill net was A. lesciscus (61.61%). Temporal distribution in fish abundance within and among the species varied significantly (p<0.05), with most species reducing significantly in abundance after the 10th week of specimen collection. Cross-correlation analysis revealed strong positive associations, especially, between the Tilapia species and with C. gariepinus (r>0.60). the findings of this study should fast-track cost-effective and sustainable exploitation of inland freshwater fishery