Growth, mortality, exploitation, and recruitment patterns of Labeobarbus altianalis (Boulenger, 1900) in River Kuja-Migori, Kenya

Abstract

The Ripon barbel, Labeobarbus altianalis, a riverine fish found in the Lake Victoria Basin is regarded as species of less concern, but it is vulnerable to overfishing and population decline. This study aimed at determining growth, mortality, exploitation rate, and recruitment patterns of L. altianalis (Boulenger, 1900) in River Kuja-Migori. A total of 1,217 specimens with overall total lengths ranging from 9.5-41.5 cm (mean 28.5 ± 2.7) were collected monthly from January to December 2021. The fish were caught using an electrofisher in wadable areas and monofilament nets in deeper areas. Electronic length frequency analysis (ELEFAN) software in Fish Stock Assessment Tools (FiSAT II) program was used to analyze data. Natural mortality (M) Fishing mortality (F) and total mortality (Z) coefficients were 0.15 year-1, 0.52 year-1 and 0.67 year-1 respectively. The asymptotic length (L∞) was 44.94 cm TL while the instantaneous growth rate (K) was 0.15 year-1. The exploitation rate was 0.44 year-1 and the length-based growth performance index (Ø’) was 3.03. Results indicated that the longevity of L. altianalis was 9 years. Recruitment occurs throughout the year with bimodal annual recruitment peaks coinciding with the two rainy seasons in the region. This study provides important information for developing management advice for the L. altianalis riverine fishery.

Keywords

• Ripon barbel
• riverine
• fishery management
• Lake Victoria basin