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Aquaculture Environment Interactions

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AEI 1:107-115 (2010)  -  DOI:

Recapture of cultured salmon following a large-scale escape experiment

Ove T. Skilbrei*, Terje Jørgensen

Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway

ABSTRACT: A large-scale escape experiment using 1031 adult Atlantic salmon Salmo salar L. was performed in the Hardangerfjord in western Norway to study the dispersal of escaped salmon, evaluate the effect of a gill-net fishery targeting escaped salmonids and test whether surface trawling is an effective way of recapturing escaped salmon in a large fjord system. The salmon of mean weights 1.56 and 5.5 kg were released from 2 commercial fish farms in late September 2006. All fish were tagged with external tags, and 48 were also equipped with acoustic transmitters. A surface pair-trawl (50 m wide and 8 m deep) was constructed to optimize catchability and maneuverability in the fjord environment. Trawling was unsuccessful, and caught only 6 simulated escapees. Telemetry data confirmed that the fish were available along the towing tracks, and we assume that towing speed and/or trawl size may have been suboptimal with regard to avoidance by fish in the fjord environment. Gill-netting proved to be an efficient method of recapture. The total reported recapture rate (of 114 fishers) was 40%, but a significantly higher recapture rate (67%) of the more highly rewarded acoustic transmitters, and the distribution of the fish in time and space, suggest that the actual catch may have been substantially higher. Approximately 90% of the catches were taken within 40 km of the release sites over the course of 4 wk. We conclude that a significant proportion of escaped adult salmon can be recaptured if the catch effort within the fjord basin is widespread and lasts for at least 4 wk.

KEY WORDS: Escaped cultured salmon · Fish farms · Recapture · Gill-net · Trawling

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Cite this article as: Skilbrei OT, Jørgensen T (2010) Recapture of cultured salmon following a large-scale escape experiment. Aquacult Environ Interact 1:107-115.

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