Fisheries management based on gear selectivity of a tropical reservoir, Lake Nasser, Egypt

Abstract

Lake Nasser, a large man-made tropical reservoir, is located in the southern part of Egypt. The lakes’ fisheries have undergone a steady decrease during the last 10 years obscuring its potential for sustainability. Fisheries assessment study based on the fishing activities is essential to attain reliable information for construction a management plan to achieve rational and sustainable exploitation. Spatial and landing site surveys were conducted during the period from 2016 to 2017. More than 300 random fishing boats were examined to investigate their fishing gears characteristics, species composition, mean trophic level and catch per unit effort. More than 13,000 fish specimens from the catch were sampled and investigated for the gear selectivity study. The results indicate that trammel nets, gill nets and long-lines are the main fishing methods used. Thirty-four fish species were recorded in the lake, 6 of them were dominant, namely; Oreochromis niloticus, Sarothrodon galilaeus, Coptodon zillii, Lates niloticus, Alestes baramoze and Hydrocynus vittitus. The lake exhibits spatial variations in its productivity as the southern part is more productive. The time series of size and CPUE showed a high exploitation rate for the most important commercial fish species in the lake by the fishing gears used. Measures for fishery management based on gear selectivity are suggested for sustainability.