Evelyne Ndiritu, Cosmas Munga, Melita Samoilys

Abstract

Handline or hook and line is a commonly used fishing gear in Kenya’s small scale coastal and marine fishery. The most abundant catches of this gear is made up of the fish family Lethrinidae. Despite this wide usage of the gear, there is still limited information on hook size selectivity on the target fish species. Therefore, this study assessed hook size selectivity on catches of lethrinids by evaluating mortality and exploitation rates, proportion of immature and undersized fish individuals and catch per unit effort (CPUE). Fish catch surveys were conducted for ten days in a lunar month from July to December 2021 in the selected fish landing sites of Mkunguni, Mwaembe, Kanamai and Mtwapa along the Kenya coast. Hook sizes were categorized into three categories and comprised of large (No. 6-8), medium (No. 9-11) and small (No. 12-14) hooks. Four lethrinid fish species dominated the catches, Lethrinus borbonicus, Lethrinus lentjan, Lethrinus rubrioperculatus and Lethrinus mahsena, collectively accounting for 82.3% of the total landings. L. lentjan was found to be grossly overexploited, L. borbonicus lightly overexploited and L. rubrioperculatus and L. mahsena underexploited, in reference to E_max, E_0.1 and E_0.5. Lengths at first capture (L₅₀) for the four dominant species were below length at maximum yield per recruit (L_opt) and length at first maturity (L_m). Proportions of juveniles and individuals below optimal lengths were high in small hooks (41-71% and 49-77%) compared to medium (35-51% and 45-62%) and large (<11% and 3-19%) hooks, respectively. CPUE differed across hook size groups (p < 0.05), with the small hooks recording significantly low CPUE (p < 0.05). Large hooks captured low number of juveniles and undersized individuals and resulted in higher CPUE. Large hooks are therefore recommended for the small-scale handline fishery, given that they are ecologically and economically beneficial.