Negative impacts of the sea lice prophylactic emamectin benzoate on the survival of hatchery released salmon smolts in rivers.

Negative impacts of the sea lice prophylactic emamectin benzoate on the survival of hatchery released salmon smolts in rivers. Aquat Toxicol. 2020 May 23;224:105519 Authors: Lennox RJ, Salvanes AGV, Barlaup BT, Stöger E, Madhun A, Helle TM, Vollset KW Abstract Emamectin benzoate (EB) is a prophylactic pharmaceutical used to protect Atlantic salmon (Salmo salar) smolts migrating out of rivers and into the ocean against sea lice parasites. Randomized control trials comparing the marine survival of smolts treated with EB to a control group is used to calculate the fraction of marine mortality attributable to sea lice parasitism. However, it is assumed that there is no baseline difference in survival induced by the application of EB treatment. We used a combined laboratory and field study approach to investigate the potential impacts of EB treatment on behaviour and survival of hatchery-reared Atlantic salmon in western Norway. In aquaria experiments, EB-treated salmon smolts did not differ significantly in exploratory behaviour. Fish from treated groups responded similarly to simulated predator attack with spontaneous escape and elevated gill beat rate. Three rivers in the Osterfjord system of western Norway were selected for field experiments, Dale, Vosso, and Modalen. Dale River smolts were treated with intraperitoneal EB injections and had lower probability of detection in a wolf trap downstream of the release site than control smol...
Source: Aquatic Toxicology - Category: Toxicology Authors: Tags: Aquat Toxicol Source Type: research