Development of a food consumption model for Nile perch, its population dynamics and food selectivity indexes. Essay

1.0 Introduction
Nile Perch, Lates niloticus (Linnaeus, 1758) is a fish species belonging to the family Centropomidae. It is indigenous to the River Nile system (Froese and Pauly, 2009) and once occurred in an earlier Lake Victoria which dried up many millions years before the present Lake Victoria was formed (Pringle, 2005). It was prevented from re-inhabiting Lake Victoria by the Owen Falls.
The fish grows to a huge size of approximately 205 cm (Kaufman, 1992) and is very prolific in reproduction having a mean fecundity of about 7.5 million eggs (Asila and Ogari, 1988). The fish is predatory mainly feeding on insect larvae, prawns and other fish species (Ogari, 1985).
Since its introduction into Lake Victoria in the late 1950s, there has been significant and steady decline in the mean catch rates of indigenous fish species in the Nyanza Gulf. This is due to a combination of factors including indiscriminate fishing gear, unsustainable fishing practices and most importantly the predatory effects of Nile Perch (Awange & Ong'ang'a, 2006). It has dominated the catches in the Nyanza Gulf for more than two decades. However, no detailed studies have been conducted to determine its impact on the resiliently abundant fish species in Nyanza Gulf (Awange & Ong'ang'a, 2006). Past research has mainly concentrated on food item occurrence and composition. Information on food consumption per unit biomass and the calorific contribution of different food items to the diet of Nile Perch has not been studied in the Nyanza Gulf. This study will focus on the development of a food consumption model for Nile perch, its population dynamics and food selectivity indexes.
1.1 Statement of the problem and Justification
The annual loss of the prey fish species due to Nile Perch predation in the Nyanza Gulf has posed serious concern to the fishermen. Fish species which once were of high prevalence in the diet of riparian inhabitants and in the market have been decimated to extremely low densities to the extent that they have no economic importance (Getabu et al., 2003). It is expected that by management of Nile Perch population through fishing, the once dominated species can recover and contribute positively to the fisheries. This can only be possible through an assessment of the impact of the predatory Nile Perch on other species and the possible harvesting of Nile perch to the level at which its impact is not deleterious to the fish communities of the Nyanza Gulf. This will be achieved by estimating the food consumption per unit biomass, quantifying the amounts of the other fish species removed annually and making recommendations on the appropriate fishing levels of Nile perch. This information is at present lacking.
1.2 Objectives
The general objective is to conduct an assessment of food consumption per unit biomass of Nile Perch, Lates niloticus (Linnaeus, 1758) and its effect on prey fish species in the Nyanza Gulf of Lake Victoria, Kenya
Specific Objectives
1. Estimate the food consumption per unit biomass of L. niloticus in the Nyanza Gulf, Lake Victoria.