No abstract

Fish protein is regarded as quality protein being rich in essential amino acids with a high digestibility value. The biochemical composition of the fish differs with the change in habitat as well as season. Samples of freshwater catfish (Clarias gariepinus) from Upper Jebba Basin, Nigeria were analyzed during the dry and wet seasons to study the variation in proximate composition of nutrients and mineral content using standard procedures in dry weight basis. The results revealed the presence of the moisture content with an average mean of 4.26 ± 1.04% in dry season while wet season recorded 5.63 ± 1.27%. The ash content in dry and wet season is 6.10 ± 0.85% and 4.66 ± 0.46% respectively while the crude fibre were generally low with significantly variation (P<0.05) between 0.84 ± 0.12% in dry months and 0.57 ± 0.25% in wet months. The average mean values of crude protein were slightly higher at 64.47 ± 0.58% in wet months than 63.10 ± 2.10% in dry months. Variation in crude fat content for both season were within a narrow range with an average mean of 4.03 ± 0.16% and 4.09 ± 0.03% for dry and wet season respectively. Average Nitrogen Free Extract (Carbohydrate) of 20.76 ± 1.43% in dry season was comparatively higher than 19.86 ± 1.55% in wet months. The mineral composition of the fish in both seasons varied significantly (P<0.05) in Ca, K, Cu and Zn% mean concentration.

Artisanal fisheries contribute to sustainable livelihoods of people in several ways accounting for more than 80% of total fish production in Nigeria. Climate change arising from global warming, increasing temperature, stratification and changes in ecosystem processes brings flooding, precipitation, evaporation, run-off and flow with potential serious negative impacts on fish assemblages and productions, fishing activities, fishers catch per unit effort, fish breeding, morphology, resistance to species invasion, wild fish seed supply, fish meal and oil and likelihood of spread of vector-borne diseases. Climate change could also extirpate fish population in lakes. Fishing gears, fishing processing and marketing, fishing periods could be affected and at the extreme total abandonment of artisanal fisheries could occur on account of climate change. Understanding climate change and its impacts on the ecosystem will provide accurate decision, capacity building and adaptive management in tackling the problems as it will provide practical, scientific, technical and socio-economic actions to mitigate the challenges currently and in the future. Study of vulnerability of artisanal fisheries to climate change in the likelihood of episodic events of risk exposure, sensitivity and adaptive capacity should be the focus of scientific research in this decade. Climate change will produce synergistic and cumulative effects with considerable uncertainty to the extent, magnitude, rate and direction of changes and impacts. Thus, high confidence predictions models of climate change perturbations on fish response in terms of feedbacks, critical thresholds, adaptations, migrations, breeding, and recruitment and so on could mitigate the impacts and ensure sustainability of artisanal fisheries in Nigeria. Alterations in their food-web processes and interactions, species invasion and spread of vector-borne diseases could also result from the effects of CC. Rosenzneig [7] reported that surface water temperatures have warmed by 0.2 to 2°C in lakes of Europe , North America and Asia with stratified periods advanced by up to 20 days and lengthened by 2-3 weeks. This is also true in Africa as a result of increasing gas emissions. Since fish are cold blooded, they are very sensitive to temperature changes. Any increase in temperature above the tolerance limit in their habitat will surely have serious negative effects on fish physiology especially in the supply of oxygen to their tissues. CC will impact on the spawning success of fishes spatially and temporally. This is because time and locations of spawning of several species of fish are linked to physical conditions such as temperature, currents etc, as well as biological factors like food. Changes in these conditions on account of CC would therefore impact negatively on the spawning of fishes in these habitats. Likewise, food and feeding of fish would be affected as plankton production in aquatic ecosystem is linked to physicochemical variables of the ecosystem which could be seriously ...