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

Abstract

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.

A protocol for identifying suitable biomarkers to assess fish health: A systematic review

“…Pollution stress has well-known effects on reproductive and endocrine parameters in fish [150], however, only a few studies were identified in our review that specifically examined these biomarkers (S19 Table). Vitellogenin (VTG) is a precursor egg yolk protein found in the blood or haemolymph in females of nearly all oviparous species [151]. VTG levels are highly sensitive to endocrine disrupting chemicals (EDCs), and are affected by exposure to some xenobiotics including PCBs and Cd [5].…”

In situ biomonitoring of caged, juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Lower Duwamish Waterway

“…However, the consequences of altered feeding status on biomarker response can be difficult to estimate. For example, a 30 day starvation experiment using rainbow trout showed alterations in EROD activity after 30 days (Hanson and Larsson, 2007). In contrast, a longer-term study, also utilizing rainbow trout, found no difference in EROD activity based on no, half or full rations for 9 weeks, though the study did report a significant reduction in glutathione S-transferase (GST) after 6 weeks (Gourley and Kennedy, 2009).…”

“…Laboratory studies are unable to duplicate true field conditions and thus may provide misleading conclusions (Hanson and Larsson, 2007; Martin-Diaz et al, 2008). Similarly, although biomarkers have been demonstrated to be effective indicators of exposure (Van Der Oost et al, 2003), biomarker data collected from field studies using wild-caught fish are subject to high inter-individual variability due to mobility of fish and varied exposure histories (Hanson and Larsson, 2007). In order to reduce this variability and to more closely resemble true field exposure conditions, a series of 8–10 day in situ caged fish exposure studies were conducted in the LDW each July, over a 4-year period (2004 – 2007).…”

Effect of different river flow rates on biomarker responses in common carp (Cyprinus carpio)

“…In studies addressing the impact of environmental contaminants on fish biomarkers, several experimental designs can be applied -laboratory studies, field studies using wild-caught fish, and in situ studies using caged fish. In laboratory studies it is not possible to duplicate true field conditions so the results obtained in such studies may provide misleading conclusions (Hanson and Larsson, 2007;Martin-Diaz et al, 2008). Field studies using wildcaught fish require investigation of the same species at each site in order to be able to compare different sites.…”

“…Since fish community structure depends on different abiotic and biotic factors present in the water body under investigation, it is practically impossible to find a species that is present at all sites of interest. Also, in wildcaught fish the high inter-variability in biomarker responses is often present due to mobility of fish and varied exposure histories (Hanson and Larsson, 2007). To minimize this problem, it is possible to conduct transplant experiments and active biomonitoring using cages has already been implemented using different organisms, including fish (Bervoets et al, 2009;De la Torre et al, 2007;Oikari, 2006;Reynders et al, 2008).…”