Abstract
The purpose of this study was to investigate the species composition and size selectivity of gillnets commonly used by the artisanal fishers in the New Calabar River, Rivers State, Nigeria. The data was collected during February-July 2018 from 3 sampling stations: SI Choba, S2 Ogbogoro, and S3 Iwofe all along the stretch of the river. Twenty-eight fish species were found belonging to 15 families. The prevalent families were Cichlidae, Mugilidae and Clupeidae representing 32.22%, 30.36% and 10.23% of the total catch, respectively. The most dominant species in terms of number were Liza falcipinnis (12.58%) and Mugil cephalous (12.26%) while in terms of biomass, the most abundance species were Xenomystus nigri (24.12%) and Lutjanus agennes (12.50 %). The girth and total lengths of the fishes ranged from 5.20±0.20 to 21.00±0.00 cm and 8.85±0.15 to 28.19±1.13 cm respectively. The length at first capture (L50%) for the most abundant species (Liza falcipinnis) was calculated to be 14.13 cm while that of L25% and L75% were 12.70cm and 15.25cm respectively. It was concluded that the gill nets used in the New Calabar River exploit fish species of small sizes and few medium sized specimens relative to species potential maximum size. It is therefore recommended that for an improved and sustainable exploitation fish stock of the New Calabar River, the use of gillnets of less than 25 mm-mesh sizes and “other gears” should be prohibited.Keywords: gill nets; species composition; mesh size; selectivity; New Calabar River
Highlights
Niger delta is blessed with rivers, lagoons, creeks and their associated wetlands that are very rich in fish and other aquatic biodiversity
**Significant at p
According to Olopade and Rufai (2014), The mean girth, total length and mean weight of the fish species are shown in the Table 6 below the girth ranged from 5.20±0.20 to 21.00±0.00 cm recorded for Brycinus longipinnis and Xenomystus nigri respectively
Summary
Niger delta is blessed with rivers, lagoons, creeks and their associated wetlands that are very rich in fish and other aquatic biodiversity. As a result of these numerous inland water bodies, fishing is the major tradition occupation in the region for the people living in riverine areas. The vast water bodies support large freshwater small-scale artisanal fisheries that support livelihood gains and those that primarily support subsistence consumption activities. The capture from inland waters are multi-species and multi-gear with a great majority of fishers traditionally operate at small-scale level to exploit the natural fisheries resources in whatever means available to them (Olopade et al, 2017). Over the past decades, these water bodies have come under increased pressure due largely to the heavy demand on freshwaters fishes, habitat degradation and water pollution. The increase in demand for freshwater fishes has led to increase in fishing effort and the use of destructive fishing gears and the consequent is stock depletion and over fishing
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