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.

1. 寄生虫病是全球水产养殖业面临的最严峻挑战之一，当前学界对采用生态解决方案防控寄生虫感染的关注度与日俱增。其中一项已被提出的解决方案为富集养殖（enriched rearing）：即在传统的低刺激养殖水箱中增设不同类型的结构，以提升栖息地复杂度。已有研究证实，此类空间富集可提升鱼类在寄生虫暴发期间的存活率，但其背后的潜在机制仍未明确。
2. 本研究针对幼年大西洋鲑（Salmo salar）与洄游性褐鳟（Salmo trutta），探究了富集养殖对其感染重要鱼类致病菌柱状黄杆菌（Flavobacterium columnare）的影响。其一，我们通过同质园实验（common garden experiment）开展天然细菌暴露试验，并使用多个鱼类种群，以解析宿主遗传背景在富集养殖效应中的作用；其二，采用全因子设计（full factorial design），将常规养殖与富集养殖的鱼类分别置于常规与富集环境中进行可控细菌剂量暴露实验，以探究养殖背景与暴露环境对鱼类存活率的相对影响。
3. 富集养殖可显著提升鱼类在天然细菌暴发期间的存活率，该效应较为稳定，在10个鱼类种群中的8个均观测到了该结果。在可控暴露实验中，无论鱼类自身的养殖背景如何，在富集环境中暴露的鱼类存活率均更高，这表明环境对疾病进程的影响更为显著。此外，富集养殖背景的鱼类在富集环境中的存活率最高，进一步支持了这类鱼类抵抗力更强的结论。
4. 综合与应用。本研究结果表明，富集养殖可提升鱼类存活率，其机制为环境改善与鱼类个体状态提升的共同作用，而宿主遗传背景的影响相对较弱。该发现对环境富集的应用时机与方式具有重要指导意义。总体而言，本研究结果显示，环境富集可有效提升鱼类在寄生虫暴发期间的存活率，从而减少水产养殖业中抗生素的使用。