Length-weight Relationships and State of Well-being of Parachanna obscura Gunther1861, in Eleyele Reservoir, Southwestern Nigeria

Abstract

The knowledge of length-weight relationship parameters has numerous practical applications in fishery research and management. However, there is currently dearth of information on the growth pattern and state of well-being of Parachanna obscura in Eleyele Reservoir. This study therefore investigates the allometry and condition factor of P. obscura inhabiting the Eleyele Reservoir, Southwestern Nigeria. 688 specimens of P. obscura were collected from artisanal fishers’ at their landing sites on a bimonthly basis for 24 months. Standard Length (SL, cm), and Body Weight (BW, g) were measured. Length-Weight Relationships (b>3 or <3-allometric; b=3-isometric), and condition factor (K) were calculated using standard formula. Data were analysed using descriptive statistics and ANOVA at α0.05. The SL and BW of P. obscura ranged from 10.6 to 39.2 and 15.3 to 830.5 respectively. The LWR were 3.04 (male) and 2.99 (female) indicating positive allometric pattern of growth in male and negative allometric growth in female. The growth coefficient b ranged between 2.877 in July and 3.348 in May, with very significant coefficient of determination r2 for all the months. Variations recorded in the b value of different size groups showed positive allometric growth in 10.1 cm -15.0 cm, 15.1 cm -20.0 cm and 20.1 cm -25.0 cm, but negative allometric growth in 25.1 cm -30.0 cm and 30.1 cm -40.0 cm. The maximum (1.54 ± 0.12) K was noticed during March 2016 and the minimum (1.30 ± 0.7) K in September 2015. Significant variation occurred in K with size groups. The mean K value in females (1.43 ± 0.21 and 1.44 ± 0.20) was higher than males (1.40 ± 0.18 and 1.42 ± 0.17) for 2014-2015 and 2015-2016, respectively. The results indicated that P. obscura were thriving very well in Eleyele Reservoir.