Community Research and Development Information Service - CORDIS


SUMBAWS Report Summary

Project ID: Q5RS-2002-00730
Funded under: FP5-LIFE QUALITY
Country: United Kingdom

Physiological consequences and benefits of premature return of infested sea trout

The physiological consequences of “premature return” to freshwater in response to sea lice infestation were examined in laboratory studies by infesting seawater-acclimated wild sea trout smolts with L. salmonis and either,
1) Maintaining fish in seawater or
2) Returning fish to freshwater 19 days post infestation (with respective non-infested controls for both groups).

Following freshwater return, the mean infestation intensity and number of mortalities were significantly reduced compared to fish maintained in seawater. Plasma concentrations of chloride and lactate were significantly higher in the seawater infested group than in all other groups after 21 dpi. Liver glycogen content was significantly decreased following sea lice infestation and remained at a reduced concentration in the seawater infested group. There was evidence of recovery of liver glycogen content following return to freshwater. Plasma cortisol concentration increased in both infested groups at 14 dpi compared to non infested controls, but returned to control levels in fish returned to freshwater. These results suggest that premature return to freshwater confers considerable physiological benefit and increased survivorship of sea trout post-smolts previously infested with L. salmonis.


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