MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(HAN-1117-545486) Effects of caging and feeding on selected biomarkers in rainbow trout (Oncorhynchus mykiss).

Hanson, N¹, Larsson, A¹, ¹ Applied Environmental Science, Goteborg University, Goteborg, Sweden

ABSTRACT- Many human made chemicals have had adverse effects on ecosystems, something that has led to an increasing need for environmental monitoring and ecological risk assessment. Historically, monitoring and risk assessment of pollutants has been focusing on point sources and known chemicals. During the last decade, however, monitoring of environmental pollution has started to emphasize on diffuse sources and mixtures of pollutants. This has raised a need for new strategies and methodologies in pollution monitoring. Most pollutants sooner or later end up in aquatic ecosystems. The use of biomarkers in stationary fish species has previously proved useful in monitoring of water pollution. Biomarkers are useful to demonstrate exposure to various known and unknown environmental toxicants. One drawback, however, is that suitable stationary fish species not always are available. Furthermore, natural variations in fish populations could bias the results. One way to avoid these problems is to use farmed fish. In this study, the use of biomarkers in farmed Rainbow trout (Oncorhynchus mykiss), kept in cages, has been evaluated as a potential method for assessment of total environmental pollution load. The use of farmed fish has previously been used to evaluate point sources of pollution. However, when pollution levels are low, there is an increased risk that factors other than pollution level could affect the results. Here, the factors type of caging (net-cages and plastic tanks) and feeding level (8% and 2% weekly of total fish weight) has been examined for a number of biomarkers. We found significant differences between levels of feeding for plasma concentration of Na+, hepatic EROD-activity and presence of immature red blood cells. The use of caged fish may become a useful tool in pollution monitoring, especially when there are many or unknown chemicals present. However, the results of this study indicate that good experimental design is important to avoid misleading results.

Key words: environmental monitoring, ecological risk assessment, biomarkers, fish