Variations in zooplankton diversity and abundance in five research fish ponds in northwest Amhara region, Ethiopia

Abstract

Zooplankton diversity, abundance and some selected environmental parameters of water quality were monitored in five aquaculture research ponds between December 2007 and June 2008 in North West Amhara region of Ethiopia. Bichena-I and Bichena-II fish ponds which received sub-surface water showed significantly lower (P ≤ 0.05) values of temperature and turbidity than the surface water-sourced ponds. In contrast, Amanuel, Yewela and Gozamen fish ponds that received surface water showed lower values of total hardness, conductivity, total dissolved solids, nitrate and ammonia than Bichera 1 and 11 ponds. Zooplankton diversity was determined using Margalef's index of species richness(S), Shannon–Wiener diversity index(H) and Evenness Index (E) while correlation coefficient values were used to determine the relationship of zooplankton diversity and the environmental parameters considered. The zooplankton fauna consisted of 52 species comprising 19 species of rotifers (Rotifera), 18 species of copepods (Copepoda) and 15 species of cladocerans (Cladocera). The values of all the three measures of diversity considered (S, H 1 and E) all pointed to the fact that the fish 1 ponds that received surface water were characterised by high zooplankton diversity than those that received subsurface water source. Margalef species richness (S) and Shanon-Wiener's index (H') were both highest in Yewela fish pond and lowest in the turbid Gozamen fish pond. The highest value of evenness index (E) was recorded for the Amanuel fish pond while the lowest value was in Bichena-I fish pond. The study indicated that the fish ponds replenished with water sourced from surface water bodies showed higher zooplankton diversity than those of the subsurface water sourced ponds thereby suggesting preference for surface water source as better option for achieving optimal feeding conditions for managing fish ponds in the locality. Keywords : Copepoda, Cladocera, Rotifera, Species Richness, Surface, Sub-surface Water