~ 87 ~ International Journal of Fisheries and Aquatic Studies 2022; 10(4): 87-92 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 76.37 (GIF) Impact Factor: 0.549 IJFAS 2022; 10(4): 87-92 © 2022 IJFAS www.fisheriesjournal.com Received: 12-09-2022 Accepted: 17-10-2022 George Owiti Osure 1] Department of Biological Sciences, Pwani University, P.O. Box 195-80108, Kilifi, Kenya 2] Faculty of Agriculture and Natural Resources Management, Kisii University, P.O. Box 408 - 40200 Kisii, Kenya Albert Getabu Faculty of Agriculture and Natural Resources Management, Kisii University, P.O. Box 408 - 40200 Kisii, Kenya Christopher Mulanda Aura Kenya Marine and Fisheries Research Institute (KMFRI), P.O. Box 1881 - 40100, Kisumu, Kenya Reuben Omondi Faculty of Agriculture and Natural Resources Management, Kisii University, P.O. Box 408 - 40200 Kisii, Kenya Evans Basweti Faculty of Agriculture and Natural Resources Management, Kisii University, P.O. Box 408 - 40200 Kisii, Kenya Corresponding Author: George Owiti Osure 1] Department of Biological Sciences, Pwani University, P.O. Box 195-80108, Kilifi, Kenya 2] Faculty of Agriculture and Natural Resources Management, Kisii University, P.O. Box 408 - 40200 Kisii, Kenya Population parameters and exploitation rates of four commercial fish species of Awach Kibuon River: Towards sustainable management of riverine fisheries of the Lake Victoria Basin George Owiti Osure, Albert Getabu, Christopher Mulanda Aura, Reuben Omondi and Evans Basweti DOI: https://doi.org/10.22271/fish.2022.v10.i6b.2751 Abstract The study estimated population parameters of four leading commercial fish species of Awach Kibuon River in Lake Victoria Basin, Kenya to inform management interventions for sustainability. Length data were collected monthly from January to December 2020 and length-frequency analysis conducted in FiSAT II software utilizing ELEFAN I Routines. Exploitation rates (E = 0.63) for Protopterus aethiopicus (Heckel, 1851) and (E = 0.56) for Clarias gariepinus (Burchell, 1822) indicate overfished stocks (E > Eopt) whereas exploitation rates (E = 0.31) for Synodontis victoriae (Boulenger, 1906) and (E = 0.32) for Oreochromis niloticus (Linnaeus, 1758) signify optimal exploitation (E = Eopt). There were year-round recruitments with bi-modal annual pulses in the populations of O. niloticus, S. victoriae, and P. aethiopicus. These results are crucial for sustainable management of riverine fisheries in the Lake Victoria Basin. This study recommends reduction of fishing pressure on P. aethiopicus and C. gariepinus to enhance their sustainability. Keywords: Population parameters, recruitment patterns, growth rates, mortality rates, exploitation rates 1. Introduction Estimation of fish population parameters is important in understanding fish stock status and subsequent planning for their sustainable management [1, 2] . Natural fish populations are dynamic owing to varying environmental conditions and changing fishing pressures [3] . Recruitment-, growth-, and mortality rates are the main drivers of fish population dynamics [4, 5] . Fish populations increase in size if recruitment and growth rates exceed mortality losses and decrease if mortality rates are higher. Fish population parameters are influenced by environmental conditions and life-history strategies of the fish species [6] . Long-lived species exhibit bigger asymptotic lengths (L∞), low natural mortality rates (M), and low growth curvatures (K) while short-lived species exhibit smaller asymptotic lengths (L∞), high natural mortality rates (M), and high growth curvatures (K) [7] . Recruitment refers to the number of fish that survive the spawning and nursery grounds to enter the fishing grounds in a year. It is highly variable in natural fish populations, varying from year to year [1] . The causes of high variability are unclear but competition, cannibalism, predation, diseases, and water temperature are known to influence eventual recruitment to adult fish populations [9, 10] . Growth refers to increase in length or weight of fish in the population over time. Growth of individual fish in fish populations is described by the von Bertanlanffy growth model: L(t) = L∞ × {1- exp (-K×(t-t 0 )), where L∞ is the asymptotic length, K is the rate at which fish grows towards this size, and t 0 is the hypothetical age of fish at which the length of fish is zero [9] . In temperate fish species, growth is measured by use of annual and seasonal growth rings on scales, otoliths, vertebrae, and fin rays but in tropical fish growth is estimated by length-frequency analysis due to lack of distinct seasonal and annual growth rings. Commonly estimated growth parameters include asymptotic length (L∞) and growth curvature (K) which are unique to each species but may vary for different populations of the same species [9] .