Potential fish yield and Physico-chemical characteristics of Weija reservoir in Ghana
The Weija Reservoir is an important resource for the production and supply of potable water, fish and irrigation services in Ghana. The study was undertaken to estimate the potential fish yield of Weija Reservoir to provide information for planning and management and to address the challenges of paucity of information on the potential fish yield of reservoirs in Ghana. Fish and water samples were collected monthly between March and December 2011 at Intake, Machigeni and Galilea sampling stations in the Weija Reservoir. Based on the physico-chemical parameters evaluated, the Weija Reservoir is adequate for fish survival, growth and production despite indications of low levels of organic contamination. Estimates of mean fish yield and potential fish yield for the three (3) stations based on morpho-edaphic index indicate that Machigeni has the highest yields followed by Intake and Galilea due to differences in anthropogenic activities, contamination and species richness. Monthly variations in potential fish yield and physico-chemical parameters follow similar pattern at all three sites with Machigeni recording the highest values and Intake the lowest. For the section of the reservoir sampled, the mean potential fish yield was 68.27 kg ha-1 while the mean fish yield was 229.45 t yr-1 giving indication of declining fish yield compared to the earlier life of the reservoir which is attributable to physico-chemical, environmental, biological and anthropogenic changes. For successful fisheries management, regular monitoring of the fish species as well as control of fish habitat and environmental degradation are recommended.