Comparative Study of Length-Weight-Relationship (LWR) of the Fishes and Fishing Gears use in Goronyo Reservoir and River Rima in Sokoto State, Nigeria

Authors: Gusau IA*

DOI: 10.23880/izab-16000283

Volume 4, Issue 2

Abstract

Length - weight relationship is an important fishery management tool in estimating the average weight at a given length group and in assessing the relative wellbeing of a fish population.This study was conducted for six months, from April to October 2018 in both Goronyo reservoir (GR) and downstream River Rima (RR) to compare and evaluate the Length-Weight- Relationship (LWR) of some important commercial fishes and fishing gears used in the two water bodies. Five (5) and three (3) fish landing sites were purposively selected from Goronyo reservoir and River Rima because of their high fish landings and 10 fishermen were randomly selected and their catches monitored. The length and weight values were transformed into natural logs through the regression equation Log W = a + b Log L using SPSS computer software version 22. A total of 66 fish species were identified from the two water bodies, Goronyo reservoir accounted for 28 while River Rima accounted for 38 and 22 species were common in both water bodies. The mean b values of the LWR indicated that Latesni loticus, Bagrusbayad macropterus and Auchenoglanisocci dentalis exhibited positive allometric growth pattern in both water bodies, but slightly higher in Rima River (b = 3.9, 3.51, 3.7 in Rive Rima and 3.8, 3.04, 3.5 in Goronyo Reservoir) respectively. The least mean b values (b = 2.01) of LWR was recorded in respect of Synodontisgobroni in River Rima while Labeocoubie exhibited the highest b value of 3.93 in River Rima with SE value of 0.392. Gill nets were the most frequent gear used in Goronyo reservoir, and the least (3.14%) was cast net while hook and lines were almost equally used in both water bodies. In conclusion, the positive allometric growth pattern exhibited by Latesniloticus, Bagrusbayad and Auchenoglanisocci dentalis indicated favorable aquatic environments for the species to thrive well, therefore management practices should be centered on maintaining these aquatic environments. Labeocoubie should be re-introduced in both water bodies because they exhibited positive allometric growth pattern despite expected predation from Latesniloticus and fishing mortality. More attention should be given to the types of gears used in the water bodies in order to avoid catching smaller fishes. Selective gears like gillnet must conform to the Sokoto State Fisheries Edict of 1988 in order to protect heavily fished species such as Synodontis species from being over exploited. Finally, more studies are recommended to determine the effect of sex on LWR of some fish species in the two water bodies.

Keywords: Trophy Cascades; Fisheries Edict; Goronyo Reservoir; River Rima; Fishing Gears

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