Proliferative Kidney Disease in Sympatric Naturally Reproducing Populations of Rainbow and Brown Trout in Southern Peri-Alpine Germany

The decline of central European salmonid populations is exacerbated by global warming impacts on disease and interspecific competition. In this context, sympatric naturally reproducing populations of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta were sampled in three rivers in southern Germany where the myxozoan parasite T. bryosalmonae, the causative agent of the temperature-associated proliferative kidney disease (PKD), is widely distributed. As expected, parasite prevalence and kidney hyperplasia increased from summer to autumn while decreasing with fish total length. Parasite infection intensity was greater in brown trout than in rainbow trout. With ongoing climate change, this difference in species vulnerability may lead to higher prevalence of PKD in brown trout creating a competitive disadvantage.