Community Research and Development Information Service - CORDIS

Efficacy of Substance EX treatment on wild sea trout (Scotland)

Sea trout smolts were PIT-tagged and a subsection were treated with a prophylactic treatment (Substance EX) designed to protect fish against sea lice infestation. Treatments took place in NW Scotland at the Manse Loch System (2003-2005) and Shieldaig (2004-2005). Despite problems with low water levels and lack of returns of fish at both sites, encouraging results were found. Whilst prophylactic treatment had no significant effect on survivorship, length or weight there were significant effects on condition factor between the treated and control groups. For example at Shieldaig in 2005 significant effects for EX-treated fish were observed using both Fultonęs K and Wr as indices of condition factor. This suggests that EX-treated fish were subject to lesser constraints on their growth at sea and this may have significant impacts on their subsequent growth to adulthood and reproduction. This is of particular importance to stock conservation because of the allometric relationship between female size and fecundity.

Reported by

University of St Andrews, Gatty Marine Laboratory
East Sands
KY16 8HL St Andrews, Fife
United Kingdom
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