Seasonality in the photosynthetic productivity and biomass of phytoplankton in Lake Tinishu Abaya (Rift Valley, Ethiopia): The basis for fish production

Abstract

The present study was undertaken to investigate the photosynthetic productivity and biomass of phytoplankton for Lake Tinishu Abaya to observe the potentiality of the lake water for fish production. The study was carried out from January to December 2016. For the analysis of various physicochemical parameters, water samples collection was taken from two predefined sampling stations (open-water and nearshore). Biomass of phytoplankton was measured as concentration of chlorophyll a. Primary productivity of phytoplankton was measured at the open station within the Euphotic depth using lightdark bottle technique. It was observed from the results that the light-saturated rate of photosynthesis (Amax), ranged from 0.62 g C m-3 h-1 to 2.02 g C m-3 h-1 and biomass-specific rate of photosynthetic productivity at light saturation (Pmax) ranged 0.02 g C (mg Chl a)-1 h-1) to 0.106 g C (mg Chl a)-1 h-1). The hourly integral photosynthetic production (∑A), varied between 0.247 g C m-2 h-1 and 1.022 g C m-2 h-1, whereas the calculated pattern of variation for the daily integral rates of photosynthesis (ΣΣA) was ranged 5.43 g C m-2 d-1 to 9.194 g C m-2 d-1. The concentration of phytoplankton biomass (chlorophylla) was varied from 18.97mg/L to 65.05 mg/L. Based on the results of the study on various physicochemical factors, photosynthetic productivity and biomass of phytoplankton, it was concluded that the water of Lake Tinishu Abaya was chemically and biologically productive which supports most aquatic lives, production of fish, and other related multidimensional uses.

Morphometric relations and diet compositions of Nile tilapia Oreochromis niloticus (Linn. 1758) in Lake Tana Gorgora gulf, Ethiopia

“…Fisheries and Aquatic Sciences particular (Assefa & Getahun, 2015;Engdaw et al, 2013;Tefera et al, 2019;Tesfaye et al, 2020). The species is distributed in many tropical and subtropical African aquatic systems and also native to Lakes of Tanganyika, Albert, Edward, Kivu, Chad and throughout Nile River basin (Njiru et al, 2004;Shipton et al, 2008;Yirga & Brook, 2018). O. niloticus is distributed in all inland waters of Ethiopia including lakes, rivers reservoirs and swamps contributing 60% of the total landings of fish (Fetahi et al, 2017;Tesfaye et al, 2020).…”

“…Despite numerous studies have been conducted and a great deal of information is available on the food and feeding habits of O. niloticus from various Ethiopian inland water bodies (Assefa & Getahun, 2015;Fetahi et al, 2017;Getachew, 1993;Negassa & Prabu, 2008;Tefera et al, 2019;Teferi et al, 2000;Tesfahun & Temesgen, 2018;Tesfaye et al, 2020;Tudorancea et al, 1988;Yirga & Brook, 2018), a consistent pattern has not yet emerged. According to the above mentioned studies, O. niloticus in Ethiopian inland water bodies was predominantly considered as omnivorous, mainly consuming phytoplankton, zooplankton, detritus and other aquatic macrophytes.…”