Population Dynamics of Labeo senegalensis (Valenciennes, 1842) from Roseries Reservoir

Abstract

Fishery stock assessments and management provide valuable insights into various aspects, including fish growth patterns, recruitment, mortality rates, exploitation rates, and stock biomass. This study estimated the population dynamics parameters of Labeo senegalensis using FiSAT II software and analyzed length-frequency data collected from four sites in the Roseries Reservoir, Sudan. The von Bertalanffy growth model was applied to analyze growth patterns. Key parameters include asymptotic length L∞ and growth coefficient K derived from the von Bertalanffy growth function. The relative yield per recruit (Y/R) and relative biomass per recruit (B'/R) were calculated as exploitation functions to determine biological reference points. The exploitation rates at the maximum exploitation rate (Emax) were derived for 0.1 (E0.1) and 0.5 (E0.5) of the virgin biomass (E0) using the Knife-edge option. Structured virtual population analysis was conducted using FiSAT II software, incorporating parameters such as L∞, K, M, and F. The von Bertalanffy growth parameters were determined, with an asymptotic length (L∞) of 54.60 cm and a growth coefficient (K) of 0.260 yr.⁻¹. The recruitment patterns indicated a peak from April to August, coinciding with the rainy season. The annual rates of total mortality (Z), natural mortality (M), and fishing mortality (F) were calculated as 1.06 yr.⁻¹, 0.59 yr.⁻¹, and 0.47 yr.⁻¹, respectively, reflected an exploitation rate (E) of 0.45; while the maximum sustainable exploitation rate (Emax) was identified as 0.5. These findings indicate that Labeo senegalensis in the Roseries Reservoir exceeds the exploitation edge, highlighting the need for reduced fishing pressure to ensure sustainability. Early harvesting practices and gear selectivity pose risks to the long-term sustainability of the population. Implementing size limits, seasonal closures, and effort regulations may enhance yield while safeguarding the stock.