Bacteria Found in Freshwater Tilapia Fish (Oreochromis niloticus)

CHAPTER ONE

1.0 INTRODUCTION

Fish has been one of the main foods for humans for many centuries and still constitutes an important part of the diet in many countries (Leisneret al., 1995). In Nigeria, the short supply of animal protein and the increasing human population have raised the cost of animal protein to a level almost beyond the reach of the low-income group (Ezeriet al.,2001). As a result, there is a considerable increase in the demand for Freshwater Tilapia fish is the cheapest source of animal protein. (Ladipoetal., 1981). The advantages of Freshwater Tilapia fish as a food are its easy digestibility and high nutritional value (Leisneret al., 1995). These important attributes make the commodity readily susceptible to microbial attack particularly bacteria (Adams et al., 1999). Fish flesh naturally contains very low levels of carbohydrates, and these are further depleted during the death struggle of the fish (Adams et al., 1999). This has two important consequences for spoilage. Firstly, it limits the degree of post-mortem acidification of the tissue so that the ultimate pH of the muscles is 6.2-6.5 (Adams et al., 1999). The disease breaks out in fish tanks very quickly, and you must first identify the type of disease before taking action.

The bacteria are transmitted by fish that have made contact with other diseased fish. Bacterial fish disease and infections are very common and are one of the most difficult health problems to deal with (Douglas et al., 2007). Bacteria can enter the fish’s body through the gills or skin or stay on the fish’s body surface (Douglas et al, 2007). There are four types of bacterial infections. Bacterial gill disease: The gills are the primary target. Systemic bacterial disease: bacteria invade the fish’s body and damage internal organs, bacterial body ulcers: Lesions on the fish’s body that can be shallow or deep and fin rot: Most likely resulting from environmental stress. (Douglass et al., 2007). Secondly, the absence of carbohydrates means that bacteria in the fish immediately resort to using the soluble pool of readily assimilated nitrogenous material, producing off-odour. (Adams et al., 1999) Shellfish such as Tilapia have a particularly large pool of nitrogenous extractives. They are even more prone to raid spoilage, a factor which accounts for the common practice of keeping them alive until immediately prior to consumption (Adams et al., 1999). The speed with which a product spoils is also related to the initial microbial load on the product: the higher the count, the sooner spoilage occurs (Adams et al., 1999). Freshwater or rivers and lakes have a complex flora of microorganisms, including genuinely aquatic species and components introduced from terrestrial, animal and plant sources. (Adams et al., 1999). The scale of human activities has had a detrimental effect on coastal waters. Many shell fishes used for food out particles from a large volume of water. Suppose these waters have been contaminated with sewage. In that case, there is always the risk that enters organisms from infected individuals may be present and will be concentrated by the filter-feeding activities of shellfish (Adams et al.,1999). Also during the handling of the commodity, the natural flora of the environment may be contaminated with organisms associated with a man such as members of the Enterobacteriaceae and Staphylococcus aureus which can grow well at 30-37oc (Micealet al., 2007). By monitoring the bacteria contents of fish organs, the quality of fish can be measured since these will affect the storage life and quality of the fishery products (Kaneko et al., 1971). In order to provide a predictive capability for possible disease outbreaks and provide an opportunity to design preventive management actions, detailed information on the bacterial load and types of bacteria associated with the organs of apparently healthy Tilapia fish is needed.

AIM

To determine the bacterial microflora of freshwater fish (Tilapia).

OBJECTIVES

1. To determine the type of microorganism in the gill, skin and intestine.

2. To determine the type of microalgae found in the pond.

REFERENCES

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Cheesbrough, M. (2000). District laboratory practice in tropical countries. Parts 2 published by Cambridge University Press. Pg 13-7

Douglas, D. (2007). Identifying freshwater Aquarium fish disease. Available online at http://fishsuite101. com/article.cfm/identifyingfishdiseases.

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Ladipo, O; Fabiyi and Fatula, G.T. (1981), Marketing and distribution of fish in Nigeria. Report submitted to the federal development of fisheries, Lagos. Pg 35.