This paper describes two approaches to evaluate the use of fish macroparasites as bioindicators of heavy metal pollution at selected river stretches in Austria. Firstly changes in the diversity and richness of endoparasites of the cyprinid barbel, Barbus barbus (L.), were tested in relation to heavy metal contents in the aquatic system. Secondly, the bioaccumulation potential of cadmium, lead and zinc was assessed in the acanthocephalan, Pomphorhynchus laevis (Müller, 1776), and compared with that in the muscle, liver and intestine of its barbel host. The present results indicated that in order to validate the role of parasite community patterns related to heavy metal pollution, more investigations on food web dynamics, interelationships between parasites and the presence/absence of intermediate hosts will be essential. Heavy metal concentrations differed significantly between the organs of barbel and P. laevis (P=0·001) with levels up to 2860 fold in the parasite. The high level of heavy metal accumulation in P. laevis compared with that in its barbel host, suggests that despite variability in the parasite infrapopulation, host mobility and feeding behaviour, P. laevis is a most sensitive indicator of heavy metals in aquatic ecosystems.

This study analyses interspecific differences in anuran tadpole swimming behaviour that could influence vulnerability and therefore prey selection by dragonfly nymphs (Aeshna cyanea). Laboratory experiments showed that Bufo bufo tadpoles were almost continually and slowly in motion, which makes them easy prey for the dragonflies. Hyla arborea tadpoles were also very active and slow in swimming; in contrast to Bufo, however, they showed effective predator avoidance strategies (different habitat preferences, high evasiveness). The predation risk of Rana dalmatina larvae was low because the tadpoles were immobile and benthic, rare movements were made with high speeds. Bombina bombina is intermediate in swimming activity, velocity, and vulnerability.