Growth Patterns, Condition Factor, Sex Ratio and Length at First Maturity of Dominant Fish Species in the Menna River System, Tekeze Basin, Ethiopia

Abstract

ABSTRACT Fish biological parameters are essential for fisheries management. This study assessed the length–weight relationship (LWR), Fulton's condition factor (FCF), sex ratio and length at first maturity (L 50 ) of Labeobarbus intermedius , Labeobarbus nedgia and Labeobarbus beso in the Menna River system, Tekeze Basin, Ethiopia. Sampling was conducted monthly from June 2024 to May 2025 using monofilament gillnets with mesh sizes of 2, 4, 6, 8 and 10 cm. In total, 2127 specimens were collected, comprising 1225 L. intermedius , 501 L. nedgia and 401 L. beso . The LWR of all species were curvilinear and significant ( p < 0.001), with strong relationships between fork length (FL) and total weight (TW; r 2 > 0.90), confirming the suitability of the power function model. Pooled LWR analysis revealed negative allometric growth in L. intermedius (b = 2.91) and L. nedgia (b = 2.86), whereas L. beso (b = 3.04) exhibited isometric growth. Mean FCF values were 1.21 ± 0.17, 1.18 ± 0.16 and 1.40 ± 0.17 for L. intermedius , L. nedgia and L. beso , respectively. Sex ratios deviated significantly from 1:1 ( p < 0.05). The estimated L 50 values for female and male L. intermedius , L. nedgia and L. beso were 21.47/21.96, 18.50/20.64 and 15.27/16.73 cm FL, respectively. Applying a 20% precautionary safety margin above the L 50 of the sex with the larger maturity size (males), recommended minimum landing sizes (MLS) were 26.35, 24.77 and 20.08 cm FL for L. intermedius , L. nedgia and L. beso , respectively. For mixed‐species catches where species cannot be reliably identified, a precautionary MLS of 26.35 cm FL is recommended. These findings support sustainable management and conservation of Labeobarbus fish species in the Menna River system.