Diversity and abundance of fishes in Tekeze Reservoir, Tekeze Basin, Ethiopia

Abstract

The diversity and relative abundance of fishes from Tekeze Reservoir, Ethiopia, was studied from January 2016 to December 2017. Samples were collected from six sites using gill nets with different stretched mesh sizes (0.5–5.5, 6, 8, 10, 12, and 14 cm). Fish were identified to family and species level. Ecological indices such as Shannon-Weaver diversity index, Simpson’s diversity index, Species Evenness and Richness were used to analyze the data. All environmental variables were found in the optimum condition for fish production. The fish belonged to 15 species within four families: Cyprinidae, Bagridae, Claridae and Cichlidae. Shannon-Weaver and Simpson’s diversity indices ranged from 1.447 to 1.697 and 0.7333 to 0.7925, respectively, and Equitability ranged 0.6957–0.8718. Values for fish species diversity and equitability were higher (H′ = 1.715; J′ = 0.746) during the wet and dry-cold seasons, respectively. The index of relative importance
(%IRI) in the gill net landings were: Oreochromis niloticus, (35.5%), Bagrus docmak (22.6%), Labeobarbus intermedius (20.5%), Labeo niloticus (10.6%)
and Labeo forskalii (10.2%). The species with low relative importance (< 1%) include Clarias gariepinus, Labeobarbus nedgia, Raiamas senegalensis, Labeobarbus crassibarbis, Heterobranchus longifilis, Garra dembeensis, Bagrus bajad, Labeobarbus bynni, Labeo cylindricus, and Labeobarbus beso. The river mouth habitats had more catch composition than the pelagic. Physico-chemical parameters played a key role in the spatial variation of the fish. The study indicated decline of the fish stock in the reservoir, therefore, management plan and strategy should be in place to maintain the fish species and increase their sustainable utilization.

Keywords/phrases: Abundance, Diversity, Evenness, Seasons, Tekeze Reservoir