Population, Growth and Other Characteristics of Chrysichthys nigrodigitatus (Lacépède, 1803) (Pisces: Claroteidae) From Bui Reservoir, Ghana

Abstract

After five years of impoundment, Bui Reservoir fisheries has evolved with silver catfish, Chrysichthys nigrodigitatus among the most important commercial species. Based on standard length analyses of 162 individuals (62 males, 39 females) from post-impoundment seasonal sampling at three (3) stations, the population structure, well-being, growth type, sex ratio, length at first capture and rates of growth, mortality, exploitation, and other derived parameters of C. nigrodigitatus were estimated to provide requisite information for sustainable management. The population is composed of fewer juveniles and more males than females, with females relatively larger than males (modal size 7.0–7.9 for males and 9.0–9.9 for females). Females were physiologically better than males (79.49% of females had condition factor above 2.0 compared to 53.23% males) notwithstanding seasonal fluctuations. Unimodal length structure was observed for all seasons except for the post-rainy season with 2 modes, all of which, however, indicated a single year class and single spawning. Estimated hypoallometric and hyperallometric growth values among seasons and sexes were not significantly different from the isometric pattern. Estimated von Bertalanffy growth parameters were asymptotic size (L_∞) = 13.07 cm SL, growth constant (K) = 1.01 year,⁻¹ and length at time 0 (t_o) = 0.18. Growth performance index (ϕ') was 2.27, indicating slow growth while the lifespan was 2.73 years. Total mortality, natural mortality, and fishing mortality estimates were high (3.56, 2.44 and 1.12 respectively) while exploitation was below optimum (E = 0.32). Regular assessment of fish population, growth, and other characteristics is recommended to provide requisite information for strategic interventions for sustainable management and development of reservoir fisheries.