A preliminary study on limnological stock assessment, productivity and potential fish yield of Omi Dam, Nigeria

Abstract

This study examined the water quality, primary productivity, plankton and the potential fish yield of Omi dam for management purposes. Among the physico-chemical parameters analyzed, Ca²⁺ and HCO₃, were found to be above permissible limits ((3.90 ± 0.68, 24.50 ± 7.33, respectively). A total of 24 species of phytoplankton belonging to three major taxa were recorded. Most species were of the class chlorophyta, followed by chrysophyta then cyanophyta. The highest density of phytoplankton was in January (740 No. ml^-1), while the lowest (300 No. ml^-1) was recorded in April all in station 3. The mean density recorded for each month was 555, 333 and 410 No. ml^-1 for January, April and June respectively. A total of 23 zooplankton species was recorded predominated by rotifera, followed by cladocerans and copepod respectively. Density was highest (5.00 ind.L^-1) in station 1 in April, while it was lowest (0.32 ind.l^-1) in station 2 in June. Mean density for each month was 0.92, 2.95 and 0.57 (ind.L^-1) for January, April and June respectively for the three stations sampled. Sorenson’s index of similarity for zooplankton species between the months showed that there was similarity throughout the period of the study. There was also similarity in the phytoplankton except between the months of January and June. Mean gross pelagic primary productivity (GPP) was high (19.58 g O₂ m^-2d^-1) when compared to other water bodies. Mean potential fish yield (PFY) of 34.77 kg ha^-1 was calculated based on the morpho edaphic index (MEI). Observations are discussed and recommendations are made.

Keywords: Physico-chemical, assessment, phytoplankton, zooplankton, Sorenson.