Wittmann, Graber & Gundacker 2010
Wittmann, Graber & Gundacker 2010
WITTMANN, K.J., G. GRABER & C. GUNDACKER, 2010. Anthropogenic modification of food chains may show marked impact on levels of mercury (Hg) in fish food. In: 32nd Annual Meeting of the Austrian Society for Hygiene, Microbiology and Preventive Medicine, 17 - 20 May 2010: Abstract S9-5, 1 p.
Mercury contents of wild and cultured carp and trout were examined in Austria. A total of 1215 samples were collected in 2006-2009 at ten sampling sites. At each sampling date we recorded abiotic water parameters and collected water samples as well as fish of various age. If possible, we collected also sediment, hydrophytes, macro-invertebrates, and zooplankton. In addition, market samples and wild fish samples were collected. The samples were analysed by Atomic Absorption Spectrophotometry (total mercury: cold vapour-AAS).
Carp ponds showed higher organic turbidity, primary production and zooplankton density than sampling sites of trout. Cultured carp had double fold higher mercury contents than cultured trout. The mercury contents of trout and carp were clearly below the current regulatory guideline. Wild fish showed significantly higher mercury levels than cultured fish. Marine fish were the most highly contaminated; two butterfish samples reached levels beyond the regulatory guideline.
We found strong evidence for mercury bioaccumulation along the food chain. Overall, the food chain of farmed trout mainly fed by commercial food is comparably shorter than the food chain of farmed carps feeding also on zooplankton and macro-invertebrates. Sampling site, species, age, length, weight, gender, and season modified mercury accumulation in farmed fish. Young trout and in part also young carps displayed significantly higher mercury levels than older animals. The impact of pellet feeding and possible variations due to the origin of young fish require further investigation.
Wild carp taken in and near Vienna (Austria) from waters along River Danube, recently (1998-2006) invaded by the non-indigenous freshwater mysid shrimp Hemimysis anomala, showed markedly higher mercury levels compared to non-invaded waters. In view of the marked effect of high densities of this mysid shrimp on zooplankton composition it appears plausible that the elevated trace element levels are due to the insertion of an additional step in the food chain leading to fish (and finally to man). The impact of the anthropogenic introduction of non-indigenous animals and plants on levels of toxic components in food requires further investigation.
Austria; freshwater; rivers; range expansion; distribution; neobiota; environmental effects; mercury accumulation
Cyprinus carpio; Hemimysis anomala; Oncorhynchus mykiss