Environmental enrichment during early rearing of salmonids
2025 | 2026
Reiser, Stefan | Illing, Björn | Pohlmann, Dominique Marie | Focken, Ulfert
Environmental enrichment (EE) has gained attention as a strategy to add complexity to fish rearing systems. In juvenile salmonids, EE has been found to improve welfare, growth, and survival. While numerous studies investigated the effects of enrichment in laboratory settings, research under practical or field conditions has not been reported so far. In the present study, we implemented EE on three commercial salmonid hatcheries and compared enriched and conventional barren rearing. The study was conducted during two stages of the early rearing of brown trout and char. Eggs, alevins and fingerlings were reared in barren hatching trays and trays that were enriched with gravel (4–8 mm). Fingerlings were then reared in hatching troughs that were either enriched with a layer of sand (< 2 mm) or left without. When reared on gravel, char grew significantly better in terms of weight and length when compared to barren rearing. Brown trout were found to be smaller in body length when reared on gravel while no difference was found in body weight. Enriching hatching troughs with sand did not affect growth in both species. Farmers, however, reported behavioral changes and were very positive about using EE. Enrichment of trays and troughs could be easily implemented on the hatcheries. Farmers reported increased labor when using gravel for enrichment of trays, but not when enriching the hatching troughs with sand. To our knowledge, this is the first published study on the implementation of EE in commercial salmonid hatcheries confirming its feasibility under conditions of practice.
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