Environmental enrichment affects responses to novelty in juvenile Atlantic salmon

Le résumé fourni par la source

Mortality and morbidity can be high when farmed Atlantic salmon ( Salmo salar ) are exposed to sudden environmental changes such as transfer from freshwater rearing tanks to marine sea cages. Implementing environmental enrichment (EE) during the rearing of juvenile Atlantic salmon may increase behavioural flexibility thereby improving the ability of the fish to adapt to unexpected stress-inducing environmental change. In this study, juvenile salmon were randomly assigned to one of three different EE treatments (stones, periodic release of air bubbles, or exercise via increased water flow) or a barren control treatment during rearing in tanks in a freshwater flow-through aquaculture system with automated pellet feeding. After 40 days, randomly selected fish from each rearing tank were exposed to a novel environment challenge (NEC) by placing them in pairs in aquaria compartments, all having stones and continuous bubble aeration, for 35 days ( n = 4 pairs/treatment). The fish were hand-fed with food pellets during the NEC, with the assessment of daily feeding behaviour used as a proxy for their rate of adaptation to the NEC. In addition, the fish were fed shrimp pieces as a novel food challenge (NFC) during the final 3 days of the NEC. We found that the control treatment was not different in any behavioural measures from any of the enrichment groups. All groups showed a similar habituation pattern based on food motivation in the first nine days in the novel environment. Thereafter, fish from the stones and bubbles groups performed more effective feeding (actively searching for food and consuming more than 50 % of the daily food ration) compared to fish from the exercise group. Fish from the exercise group accepted the novel food at a higher rate compared to fish from the bubbles treatment. No treatment differences were observed in agonistic behaviour or locomotory activity. Our results suggest that changes in environmental enrichment impact adaptation capabilities and coping with novelty in different ways.

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