Experiences from a biomarker study on farmed rainbow trout (Oncorhynchus mykiss) used for environmental monitoring in a Swedish river

Abstract

Biomarkers in fish may serve as a useful tool for evaluating the pollution load in the environment and for early warning signals about new environmental threats. By employing a strategy with fish that are caged or reared in tanks, problems linked to migration and feeding status can be reduced or eliminated. Such a strategy, however, also may introduce other confounding factors linked to, for example, hierarchical behavior or disease outbreaks. In the present study, rainbow trout (Oncorhynchus mykiss) were reared in plastic tanks at four sites in the Göta älv river system (plus one external reference) in western Sweden during 2006 and 2007. Because of low population density and high water turnover in the area, pollution levels are expected to be low. Therefore, this should be a good test for the sensitivity of the methodology. Several significant differences were found between sites as well as between years, such as ethoxyresorufin-O-deethylase (EROD) activity, polycyclic aromatic hydrocarbon (PAH) metabolites in bile, and concentration of inorganic ions in blood plasma, but it also was seen that factors other than pollution could be contributing to these differences. The condition factor (CF) varied between sites, possibly because of differences in feeding resulting from variations in water turbidity. Furthermore, even the small differences in CF that were found within sites correlated significantly to several of the biomarkers. It was shown that PAHs likely are the most important EROD inducers in Göta älv and that variation over time is greater than variation between sites. Because CF differed between sites despite a standardized feeding ration, starving of the fish during the exposure period should be considered for future studies.

Spatial and annual variation to define the normal range of biological endpoints: An example with biomarkers in perch

“…The reason for this was that, for most of the variables, the normal range was wider when it was estimated from the four years in Kvädöfjärden. This is in agreement with previous studies that have shown that the temporal variation in some biomarker responses in caged juvenile rainbow trout (Oncorhynchus mykiss) in the river Göta älv in western Sweden is higher than the spatial variation [14]. Similar results have been seen for several biomarkers in perch, where runoff from land is likely to contribute to the variation between years in biomarker responses [8,15].…”

Using biological data from field studies with multiple reference sites as a basis for environmental management: The risks for false positives and false negatives

“…Here, the ratio s ind /s site varied between 1.45 and 6.89 for a total of 25 endpoints, ranging from enzyme activity to whole fish condition. A similar relationship between individual and spatial variation was observed for biochemical and physiological variables in rainbow trout that were caged at five sites in the Göta river water system in western Sweden (Hanson and Larsson 2009). Here, the ratio s ind /s site varied between 0.95 and 6.56.…”

Implications of biological factors on accumulation of persistent organic pollutants in Antarctic notothenioid fish

“…The length of the fish was measured from the front-tip of the mouth to the end of the caudal fin (total length). Body condition indexes were chosen to reflect several vital physiological functions that can be affected by POPs intake and bioaccumulation (Hanson and Larsson, 2009). Hence, condition index (KI), liver index (LI), and gonadosomatic index (GI) assess the physiological state of the body, the food reserves available for hepatic metabolism and the degree of gonad development, respectively (Fechhelm et al, 1995).…”