Effectiveness of Recommended Fat-Trimming Procedures on the Reduction of PCB and Mirex Levels in Brown Trout ( Salmo Trutta) from Lake Ontario

Abstract

For over a decade, a study reported by Skea et al. (1979, 1981) has served as a much-cited reference on the effectiveness of fish fillet fat-trimming to reduce organochlorine contaminant burdens in fish from the Great Lakes. By 1990, however, the results from the Skea study had yet to be independently replicated. In an effort to verify these results and to address other related questions about fillet fat-trimming efficacy, twenty sport-caught brown trout ( Salmo trutta) from Lake Ontario were selected for study. Total weight, total length, sex, age, and condition factor (K) for each fish were determined. One side (fillet) of each fish (including rib cage and scaled skin) was removed using standard filleting technique. The opposing fillet was trimmed using the fat-trimming procedures recommended by New York State for fat-soluble contaminant reduction. The trimming procedure resulted in substantial loss in yield (Mean: 41.6%) when compared to the untrimmed “standard fillet”, although this loss was chiefly composed of what would be generally considered as inedible or unpalatable body parts. The standard and trimmed fillets were analyzed for total fat content and for concentrations of polychlorinated biphenyls (PCBs) and mirex using standard laboratory and gas chromatographic analyses. Results indicated significant reductions in total fat (61.8%), PCB (45.6%), and mirex (44.2%) levels in the trimmed fillets when compared to corresponding levels in standard fillets. Significant statistical correlations were also found between fat content and contaminant levels in both standard and trimmed fillets. The pattern of strong and/or statistically significant correlations between such physical factors as weight, length, age, and condition, and the levels of fat content and contaminant concentrations in the fillets suggested that the common health advisory recommendation to avoid larger and older fish in order to minimize ingestion of fat-soluble contaminants is clearly warranted. Sex of fish was found to be unrelated to fat content and contaminant levels. Results of this limited study compare closely to specific findings for brown trout reported by Skea. Comparison of the results from both studies suggests that the recommended fat-trimming procedure remains consistently effective despite wide variation in the initial (untrimmed fillet) levels of contamination.