The effect of different holding conditions for environmental monitoring with caged rainbow trout (Oncorhynchus mykiss)

Enviro Toxic and Chemistry

2009

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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.

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

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

Enviro Toxic and Chemistry

2009

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“…Blood smears were prepared and stained using the method of Giemsa and Pappenheim for differential counting of blood cells 29 and sent for microscopic examination according to Undritz 30 and Lehmann and Stu¨renberg. 31 Plasma concentrations of ions and lactate were measured using an The procedure for EROD measurement is described by Hanson et al 18 Cytosolic liver samples were prepared as previously described by Fo¨rlin. 32 GR measurements were modified from Cribb et al 33 GST was measured as previously described by Habig et al, 34 adapted to a microplate reader.…”

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

“…A previous study has shown that net cages and flow through tanks can be used and compared in monitoring studies. 18 There are four possible routes for uptake of pollutants in fish; through feeding and the digestive tract, via contact between gill tissues and water, diffusion through the skin and by drinking water. 19 Fish that are kept in cages will not be able to feed like feral populations.…”

Section: Introductionmentioning

confidence: 99%

Influence of feeding procedure on biomarkers in caged rainbow trout (Oncorhynchus mykiss) used in environmental monitoring

2007

J. Environ. Monit.

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Biomarkers in feral fish can be a useful tool for environmental monitoring of aquatic ecosystems. Drawbacks, however, are that suitable fish species are not always available and that natural variations can bias the results. An alternative strategy is to use farmed fish placed in cages. There is, however, still a risk that factors other than pollution level could have an impact on the biomarkers and the observed responses in the fish. The present study evaluates the effects of feeding procedure on biomarkers in caged fish. Two feeding rations (2% and 8% weekly feeding) have been examined for a large number of biomarkers in caged rainbow trout (Oncorhynchus mykiss). Significant effects of feeding rations were found on hepatic ethoxyresorufin-O-deethylase (EROD) and catalase activity, PAH metabolites in bile, plasma ion concentrations and the presence of immature red blood cells. The influence on EROD activity and PAH metabolites seems to be caused by elevated uptake of pollutants when feeding ratios are higher. The effects on other biochemical and physiological variables are more likely caused by stress due to insufficient feeding. According to these results, valid comparison of fish groups in environmental monitoring requires standardized feeding levels.

“…Sampling and analytical methods are described in detail in Hansson et al [9]. The analytical methods for Vtg and GR are described by Parkkonen et al [12] and Hanson et al [13], respectively.…”

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

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

Förlin

Enviro Toxic and Chemistry

2010

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A signal from a biological endpoint can be considered evidence of environmental impact only if it is known that similar signals are unlikely to occur naturally. Using multiple reference sites, the normal range can be estimated. This can be defined as the span that includes 95% of the reference sites. If an investigated site is outside this range, it is interpreted as evidence of impact. The choice of reference sites is thus important for the outcome of the study. Here, biomarker levels in perch (Perca fluviatilis) at a potentially impacted site were compared to different types of reference data. The potentially impacted site was located close to a densely populated area. Four reference sites were located in relatively undisturbed areas on the Swedish Baltic coast. Furthermore, historical data from one of the reference sites were included. The present study showed that multiple reference sites are needed to avoid the risk of interpreting natural variation as impact. The number of reference sites needed depends on the desired level of statistical power. An alternative to multiple reference sites may be to use historical data to estimate the natural variation. However, historical data can include temporal variation due to factors that may not be relevant for the hypothesis that is tested, e.g., climatic variation or changed background levels of pollution.