Comparative assessment of food web structure and fisheries productivity of three reservoirs in Ghana

Abstract

Three Ghanaian reservoirs (Tono, Bontanga and Golinga) were compared through a food web modelling approach (Ecopath with Ecosim) to assess production characteristics and food web structures. The lakes differ in size and morphology, generating specific conditions for fish growth and production. While the two top fishery target species were Sarotherodon galilaeus (L.) and Oreochromis niloticus (L.) in all reservoirs, the mean trophic level of the catch was lowest in the largest and deepest reservoir (Tono) due to higher trophic level species occupying less accessible deep "refuge" habitats. The smallest lake had the highest fish production under optimal conditions of water supply (17.1 compared with 15.5 and 10.1 t/km 2 /year for lakes Bontanga and Tono), but it appears to be most vulnerable under conditions of drought. For the planning and construction of adequately sized reservoirs used for fishery and irrigation purposes, the water budget (ratio of inflow and evaporation) needs to be estimated.

Restocking of small water bodies for a post Covid recovery and growth of fisheries and aquaculture production: Socioeconomic implications

“…Total number of respondents (1) where, WAS = Weighted Average Score; TWS = Total Weighted Score; H = High; M = Moderate; and L = Low. The Sociometric Scale interval was calculated using Eq.…”

“…The size and number of fish that must be stocked influence whether the endeavour is cost-effective and long-term [10] . If stocking must be continued indefinitely, other enhancing strategies may be more cost-effective in the long run [1] . Negative effects on the environment and biota should be adequately considered, and attempts should be abandoned if negative consequences are predicted (Cowx, 1999) [21] .…”

Food Web Structure and Ecosystem Functions of the Water Source in the Middle Route of China’s South-to-North Water Diversion Project

“…Through the Ecopath model it is possible to evaluate the impacts of fishing, stock enhancement, and other activities on aquatic ecosystems; to determine the trophic level range and energy conversion efficiency of each functional group; and to understand the proportion of energy in primary producers and detritus and thus to judge the stability and development status of the ecosystem [3]. As a cutting-edge tool for aquatic ecosystem research, the Ecopath model has found widespread application in diverse ecosystems across the globe, such as marine [4,5], lake [6,7], reservoir [8,9], and river [10,11] ecosystems in different regions around the world.…”

Managing reservoir fisheries: a critical look at reservoir physical environment

“…Incorporating fisheries into ecosystem approaches for the management of inland waters requires evaluating fisheries exploitation potential and to examine feedback between fisheries, ecosystem productivity and aquatic biodiversity (Beard et al 2011). Findings by (Abobi 2020) and (Abobi et al 2021) suggest reservoirs that are exposed to human activities should be adequately assessed and ecosystem-based management measures developed to sustain the contribution of reservoir fisheries to nutrition and food security and to livelihoods. Indeed, these findings require a critical assessment of approaches to protect and enhance the physical environment of reservoirs for fish production, which is the focus of this short communication.…”

“…It has been noted that there is a positive association between invertivorous fish and reservoir size (Dos Santos et al 2017). While work done by Abobi et al (2021) indicates that fisheries productivity is inversely related to reservoir size, it was reported that the use of small reservoirs in populated semi-arid environments for both irrigational farming and fisheries production is unsustainable due to problems associated with seasonal water loss, siltation and aquatic habitat degradation. In tropical regions, precipitation and filling of reservoirs are the most critical stages of reservoir fisheries production and thus making reservoir surface area and depth important factors to consider in creating an optimal reservoir for fisheries production.…”