Data from: Rearing background and exposure environment together explain higher survival of aquaculture fish during a bacterial outbreak

1. Parasitic diseases represent one of the greatest challenges for
aquaculture worldwide and there is an increasing emphasis on ecological
solutions to prevent infections. One proposed solution is enriched
rearing, where traditional stimulus-poor rearing tanks are equipped with
different types of structures to increase habitat complexity. Such spatial
enrichment is known to increase survival of fish during parasite
epidemics, but the underlying mechanisms are still unclear. 2. We studied
whether enriched rearing affected infection of an important fish pathogen
Flavobacterium columnare in young Atlantic salmon (Salmo salar) and
sea-migrating brown trout (Salmo trutta). First, we used natural bacterial
exposures and multiple fish populations in a common garden experiment to
address the role of host genetic background in effects of enriched
rearing. Second, fish from standard and enriched rearing were
experimentally exposed to controlled bacterial doses in standard and
enriched environments in a full factorial design to explore the relative
roles of rearing background and environment of exposure on survival of
fish. 3. Enriched rearing significantly increased survival of fish during
the natural bacterial outbreak. This effect was also fairly consistent and
observed in eight of the ten fish populations. In the controlled exposure,
fish exposed in enriched environment had higher survival regardless of
their rearing background, suggesting a stronger impact of the environment
on the disease progression. Additionally, the survival in the enriched
environment was highest among the fish of enriched rearing background,
supporting the idea of their higher resistance. 4. Synthesis and
applications. Our result suggests that the enhanced survival of fish in
enriched rearing results from a combined effect of the environment and
improved fish condition, and to a lesser degree from host genetic
background. This has important implications for when and how environmental
enrichment should be applied. Overall, these results indicate that
environmental enrichment has the potential to improve survival of fish
during parasitic epidemics and thus reduce use of antibiotics in
aquaculture.