The optimum velocity for Atlantic salmon post-smolts in RAS is a compromise between muscle growth and fish welfare
It is increasingly common to rear Atlantic salmon smolts for longer periods in recirculating aquaculture systems (RAS) before transfer to sea cages. The conditions for this part of the life cycle are currently being optimized, especially the water velocity in the tanks since its impact has been corr...
| Published in: | Aquaculture |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | https://pure.uhi.ac.uk/en/publications/4e5246c9-68ee-4472-b701-ae4fa3138e8f https://doi.org/10.1016/j.aquaculture.2020.736076 https://pureadmin.uhi.ac.uk/ws/files/17033839/1_s2.0_S0044848620329987_main.pdf https://linkinghub.elsevier.com/retrieve/pii/S0044848620329987 |
| Summary: | It is increasingly common to rear Atlantic salmon smolts for longer periods in recirculating aquaculture systems (RAS) before transfer to sea cages. The conditions for this part of the life cycle are currently being optimized, especially the water velocity in the tanks since its impact has been correlated with. growth. Earlier studies indicate that higher water velocities promote growth in salmon, nonetheless, the optimal velocity and its associated health and welfare consequences are yet to be established. In the present study, we determined the effects of different water velocities on growth, muscle development and welfare to estimate the optimum velocity for the rearing of post-smolts in RAS. We divided 2400 salmon post-smolts (average start weight 80 g) into twelve tanks (200 fish per tank) and set the water velocities in four triplicate tanks to low (L) – 0.5 body length per second (BL/s); medium (M) – 1.0 BL/s; high (H) – 1.8 BL/s; and very high (VH) – 2.5 (BL/s). The velocity for the VH group was the highest tested for salmon post-smolts to date. The trial lasted for three months and organ samples were collected at three time points. Time-lapse cameras revealed a relatively even fish distribution in the tank in L and M groups. In contrast, fish in H and VH groups displayed strong schooling behavior at specific regions in the tanks. We observed a close to a linear relationship between water velocity and average growth rate, which resulted in a 5.7% higher average body weight in the VH group in comparison to the L group at termination. The condition factors of fish from the L group was lower than in the other three groups. Muscle cellularity analysis revealed smaller fibers in the L group, while bigger muscle fibers were identified in H and VH groups which contributed to somatic growth. Nonetheless, increased cases of inflammation were observed in H and VH groups. Muscle proteomics revealed decreased translation and carbohydrate activity in the L group. The overall external welfare status of the fish was ... |
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