Stock assessment and socio-economic characterization of fisheries in lake Baringo, Kenya

Abstract

The fisheries sector is significant to socio-economic development through provision of employment,income and food security. Global fisheries resources face unsustainable fishing pressure. In Kenya, unsustainable harvesting is due to use of management measures not informed by stock assessment studies. The aim of this study was to conduct stock assessment and characterize socio-economic dynamics for Lake Baringo Fisheries management. Stock assessment studies featured estimation of biological reference points, optimal fishing scenario, gear selectivity and socio-economic dynamics of fishermen and fish trader’s. Daily fish samples were taken from 40% of boats in the lake, five (5) days in a week between August 2013 and July 2014. A sub-sample constituting 40% of each fish species representing various size classes were obtained for length (to the nearest 0.1 cm) and weight (to the nearest 0.1 g) measurements. A total of 3,155 Protopterus aethiopicus, 2,769 Oreochromis niloticus baringoensis and 1,922 Clarias gariepinus were sampled. A structured questionnaire was administered to 42 fishermen and 34 fish traders’ selected randomly for socio-economics studies. Statistical analyses were conducted at 95% significance level. The steady state biomass for Protopterus aethiopicus, Oreochromis niloticus baringoensis and Clarias gariepinus was 474,779kg, 564 kg and 21,383 kg respectively. The maximum sustainable yield for Protopterus aethiopicus, Oreochromis niloticus baringoensis and Clarias gariepinus was 237,390, 451 and 10,692 kg respectively. The results of the study suggest that the exploitation rate for Protopterus aethiopicus (E = 0.68 > Emax = 0.25 yr-1) exceeded maximum exploitation rates indicating growth overfishing. Oreochromis niloticus baringoensis and Clarias gariepinus exploitation rates were at congenial state with no growth overfishing. Hence, Protopterus aethiopicus (F = 1.34 yr-1) fishing mortality’s should be reduced by 41.6% for reference maximum sustainable yield. The current spawning stock biomass-per-recruit (SSBCURR) for Protopterus aethiopicus (5.46%) and Oreochromis niloticus baringoensis (1.46%) show a level of recruitment overfishing. Logistic gear selection indicates L 50% of 63.48 cm selection of Protopterus aethiopicus before size of first maturity (85 cm) further adducing recruitment overfishing. Logistic gear selection indicates L 50% of Oreochromis niloticus baringoensis (15.57 cm) and C. gariepinus (35.08 cm) shows no recruitment overfishing. The age, traditions and culture of fishermen had effect on fishing effort. Fishermen changed gears from nets (for Oreochromis niloticus baringoensis) to hooks (for Protopterus aethiopicus and Clarias gariepinus) with age advancement and was accounted for by enhanced experience and target for high valued fish species. Shift dependence of fishing from domestic to commercial purpose relative to fishermen increased with age. Fish trade was entirely controlled by fishermen daily catches while their local and external markets had no significant difference. Management measures to control overfishing should target reduction of fish mortality rates for sustainable utilization of the lake Fisheries.