Early-life environmental enrichment promotes positive animal welfare for juvenile Atlantic salmon (Salmo salar) in aquaculture research

Format of work:

Journal Article

Event presented at / Journal Name:

Scientific Reports

Speaker / Contact Author's Name:

Sonia Rey Planellas

Speaker / Contact Author's E-mail Address:

sonia.reyplanellas@stir.ac.uk

Research aim:

Using juvenile Atlantic Salmon (Salmo salar), we tested whether provision of environmental enrichment in early life improves welfare.

Background:

Aquaculture has experienced rapid growth in the number of farmed fish species used commercially1. Similarly, there has been a significant increase in the use of fish within scientific research for aquaculture purposes2,3,4. However, compared to their terrestrial counterparts, the welfare of fish has often been overlooked, raising concerns within the public and the scientific community5. The increase in attention has stemmed from a central debate around whether fish are sentient or not6. Besides its controversial nature, recent evidence strongly suggests fish can feel pain, display high cognitive abilities, engage in complex social interactions, and experience positive and negative emotional states3,6.

Approach:

Using juvenile Atlantic Salmon (Salmo salar), we tested whether provision of environmental enrichment in early life improves welfare. Welfare indicators were measured comparing enriched to non-enriched tanks. Morphological (fin damage and body condition), physiological (plasma cortisol) and behavioural traits (activity, group cohesion, and neophobia) were recorded. Molecular expression of brain mRNA transcripts related to stress response, neuroplasticity and serotonergic system was analysed. Environmental enrichment did not affect morphological welfare indicators, activity, or cortisol. Enriched fish were more cohesive than non-enriched fish, less neophobic, with higher serotonergic turnover, suggesting enrichment mitigates against stress, promoting positive emotional states. Genes related to neuronal development and activity (bdnf and ndf1), cellular stress (hsp90 and hsp70), and serotonin synthesis (tph2) increased in enriched fish following stress, enhancing cognitive function

Key finding:

Early life experiences have long-lasting effects on behaviour and physiology, influencing development of adaptive natural behaviours. Enriching farmed environments encourages expression of natural behaviours in captive fish, promoting positive animal welfare, important for conducting valid and reproducible research and informing better management practices. Using juvenile Atlantic Salmon (Salmo salar), we tested whether provision of environmental enrichment in early life improves welfare.Our findings suggest early life environmental enrichment is advantageous for positive animal welfare by improving emotional states in captive environments, ensuring animals are free of negative experiences and able to access positive ones.

Industry or policy relevance:

Our findings also suggest that the provision of EE enhances resilience in early-life salmon, in addition to stress-coping behavioural profiles and cognitive abilities in line with improved mental states indicative of animals experiencing positive welfare.

Route for practical application:

Using EE in research can promote better welfare but also enhance the scientific outcomes. Recommendation is to use EE in the environment used for research in fish.

Confidence in findings and next steps towards realising impact:

Next step is to gather evidence that this interventions regarding EE are used.

Funders:

This work was funded by AquaExcel 3.0 Joint Research Action (EU H2020, Grant Agreement Number: 871108). PMP received a UKRI-Doctoral Training Grant (BB/M009122/1.), and MC held a Postdoctoral Grant fr