Does treatment of brown trout with the parasite causing PKD increase stocking success and boost resilience against the disease?

In Salmonidae, infections with the parasite Tetracapsuloides bryosalmonae may lead to a temperature-dependent proliferative disease of the kidney (PKD). Trout that survive infection and recover become resistant to the disease. The use of this approach to improve brown trout (Salmo trutta) stocking success was tested in three PKD-affected streams in southern Germany. Fish were treated using local spores of the parasite and kept at low temperatures (14°C) to not develop the disease. Controls were similarly kept but not treated with spores. Independent of time of stocking (winter or spring), recapture rates for both control and parasite-treated stocked trout were very low (<1%). However, recaptured parasite-treated trout exhibited lower parasite prevalence than control and wild-caught trout.