Microbiology and Spoilage Trail in Nile Perch (Lates niloticus), Lake ...

5 DISCUSSION
5.1 PHASE I: NATURAL MICROBIOLOGY OF WATER, SEDIMENTS AND
WHOLE NILE PERCH
Bacteria in aquatic environment may be categorised into two groups which include those
that are naturally present in the aquatic environment (indigenous bacteria) and others that
could be present as a result of contamination by human or animal or bird’s wastes or
contamination during post-harvest handling and processing. The general results on
microbiology of surface water, the bottom sediments and surface skin and guts of Nile
perch in connection to the aquatic environment indicate different levels of microorganisms.
5.1.1 Phase I trial 1: Water
Low counts of microorganisms in water often indicate that the water is not polluted by
animal manures or human wastes. On the other hand it implies that the water is not rich
habitat of microorganisms because it is poor in nutritional content required by the habitats
and growth of most microorganisms (Adams and Moss, 2008). Presence of E. coli is
obviously indicating possibilities of resent contamination from animals or birds. While for
presumptive Vibrio cholerae it could imply that Vibrio spp. is part of the indigenous micro
flora of the aquatic environment where it is reported to occur naturally (Popovic et al.,
1993).
5.1.2 Phase I trial 2: Sediments
The significant total viable counts results on sediments may be taken into account that the
sediments are natural reservoir of aquatic environmental (indigenous) micro flora that may
contribute to the microbial load in living fish. Sediments may be the major source of
contamination in catches/ fishes but it depends on method of fishing like trawling which
may lead to high contamination, less with nets and least with long line methods. The low
numbers of Enterobacteriaeceae, E. coli and the absence of pathogenic microorganisms in
sediments indicate that this family (Enterobacteriaceae) do not survive well in sediment as
it is only dominant in the guts of animals such as fish. It also implies that there was no
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