Population ecology of Parauchenoglanis fasciatus (gras, 1960) (siluriformes: claroteidae) in a Nigerian rainforest stream

Abstract

The biology and ecology of Parauchenoglanis fasciatus were investigated in Ikpa River, a blackwater stream in the eastern Niger Delta, Nigeria. The species exhibited a limnophilic and benthopelagic nature, predominantly occupying vegetated marginal areas, ponds, pools, and swamps with muddy bottom deposits. Monthly variations in catch numbers indicated alternating periods of population increase (February, April, July–August, and October–December) and decrease (January, March, May–June, and September). The length–weight relationship showed negative allometric growth (b = 2.793), with monthly variations ranging from 2.451 to 3.835. These variations were significantly correlated with hydrological parameters, including temperature, water level, discharge, transparency, dissolved oxygen, pH, and conductivity. Physiological analysis suggested a balance between anabolism and catabolism in the species. The Von Bertalanffy growth parameters estimated an asymptotic length (L∞) of 17.9 cm total length (TL) and a growth coefficient (K) of 0.265 yr⁻¹. Growth followed a biphasic pattern, with a rapid phase from August to December (0.72 mm month⁻¹) and a slower phase from January to July (0.23 mm month⁻¹). The growth performance index (ø`) was 1.95, while the growth strength index (K*) was 1.81, indicating an overall
slow growth rate. The estimated maximum longevity (Tmax) was 11.3 years. Mortality estimates included total mortality (Z= 0.94 yr⁻¹), natural mortality (M = 0.31 yr⁻¹), and fishing mortality (F = 0.63 yr⁻¹). The exploitation coefficient (E = 0.67) suggested that the species is overexploited.