Quality of Lake Victoria Nile Perch (Lates niloticus) at the Landing Facility as a

Abstract

The quality of landed Nile perch (fates niloticus) in Lake Victoria was investigated within two months of a preliminary survey and five months of the main study. The main objective was to establish the extent of contamination as raised by members of the public and the European Union (EU), which led to import bans between 1996 and 1999 and to provide evidence-based information to enable remedial measures that would assist in reviving confidence of the fish market. The study utilized bacterial counts and organochlorine pesticide residue concentrations in fish and the environment as parameters of pollution. The preliminary survey between September and November 2000 included interviews with stakeholders of the industry, observation visits to the landing beaches and sampling of fish and the environment for chemical and microbiological analysis using standard laboratory methods. Sampling sites included three beaches along the Kenyan shore line, Dunga, Uhanya and Usenge, and river Nyando. Observations indicated poor sanitary conditions at the landing facilities, low hygiene standards and uncontrolled human activity. Results of analysis showed high levels of bacterial contamination in both fish and environment and organoclorine pesticides residues were detected. Public awareness on environment destruction and the implications of the fish ban was established during interviews with both fishermen and processors, and was highly highlighted by the mass media. Based on the findings of the preliminary survey, the main study carried out between February and June 2001 investigated four landing beaches which included, Dunga, Usenge, Kaloka and Osieko, and one river, Yala. A total of 120 fish samples were analyzed for microbial counts and 118 for organochlorine pesticide residues. Total viable bacteria count ranged between 104-107/ cm2 on fish skin surface and total coliform count for the same was 101-104 MPN/cm2• Total viable count in beach sediment ranged between 104-106/g and total coliform count for the same was 101-104 MPN/g. Coliform bacteria counts in water ranged between 103104 MPN/100 ml. Both fish and environment were contaminated with coliforms of faecal origin in all study locations except Kaloka beach. Although the levels of bacterial counts in fish were higher than the FAD threshold levels, the microorganisms are destroyed during cooking, and should therefore pose no serious health hazard to the consumer. However, some pathogenic bacteria are known to produce heat stable toxins which can pose hazards to the consumer. The presence of faecal coliforms in fresh fish is not acceptable according to FAO standards. Poor handling could be instrumental to the high levels of bacterial contamination detected in most of the sampling sites. The study also looked at the monthly trends in bacterial contamination and the interaction between location and month. Accumulated analysis of variance showed a highly significant month and location effect (p<O.OOl) with respect to beach environment contamination by faecal coliform, and interaction between month and location was also highly significant at 5.0% confidence level. Fish surface contamination with faecal coliform was independent of season and the location effect was not significant. The study concluded that the beaches investigated were not significantly different with respect to sanitary status and hygiene attitudes, as reflected in fish surface contamination. Organochlorine pesticide residue levels ranged between 2.0 - 6280 I-lg/kg wet weight in fish liver and 1.0 - 517 I-lg/kg, wet weight in muscle. In total, 11 out of a spectrum of 13 pesticide residues were detected in fish, which included those banned for use in the Kenyan environment, i.e. Heptachlor, Endrin, HCH (BHC), Aldrin and Dieldrin. Pesticide residue concentrations ranged between 2.0 - 248 !-l9/kg wet weight in sediment, and between 1.0 - 312 I-lg/ml in beach waters. These findings identify the landing beaches as critical control points for hazards associated with fish contamination. According to FAa/WHO standards, fish and its growing environment should be completely free from any pesticide contamination. Lake Victoria environment did not meet these standards. The overall conclusion was that public concerns over the pollution of the lake environment have a basis and are paramount in that the level of contamination has a direct bearing on the market value of the lake's fish and fishery products. The study also concluded that the concerns of the EU market and import bans were justified and that the negative perception of the industry could only be reversed through deliberate efforts by all the stakeholders of the industry to control pollution. The study recommendations include a well-defined and sustainable monitoring system of the lake environment for fish and water quality. Based on the results of this study, a more comprehensive survey of the lake will be put to place, addressing other pollutants such as heavy metals and polychlorinated biphenyl's.