AEI 3:1-9 (2012)  -  DOI:

Net-biting and escape behaviour in farmed Atlantic cod Gadus morhua: effects of feed stimulants and net traits

Børge Damsgård1,*, Erik Høy2, Ingebrigt Uglem3, Richard David Hedger3, David Izquierdo-Gomez4, Pål Arne Bjørn1,5 

1Nofima, PO Box 6122, 9291 Tromsø, Norway
2SINTEF Fisheries and Aquaculture, Brattøkaia 17C, 7010 Trondheim, Norway
3Norwegian Institute for Nature Research, Tungaslletta 2,7047 Trondheim, Norway
4Department of Marine Science and Applied Biology, University of Alicante, 03080 Alicante, Spain
5Institute of Marine Research, PO Box 6404, 9294 Tromsø, Norway

ABSTRACT: Preventing farmed fish from escaping sea cages is a major challenge for developing sustainable aquaculture practices. In this study, the individual behaviour of Atlantic cod Gadus morhua to inspect and bite the net was investigated in 4 replicate multi-patch experiments, using underwater video techniques and behavioural event recording. The experimental system included a tank enclosure where cod were presented with 6 separate net panels: duplicate pairs of plain control nets and 2 different treatment panels. Four holes were made in the treatment panels, 3 of which were mended with different repair techniques including short and loose thread ends and contrasting colour repair threads. Behavioural effects of feed stimulants were studied before, during and after a feed source was placed outside the net. The cod inspected and bit the net systematically, significantly focusing on loose threads or minor damage on the net, and the fish were capable of causing severe net damage within a few days. The observed behaviours were related to hunger level and feed stimulation, and increased significantly during times when a feed source was present outside the net wall. Few bites were observed, and almost no measureable damage was recorded to plain control panels and the area around unrepaired holes during the treatment. Repairs made with white and black threads, and loose, long ends were significantly more damaged than repairs made with short thread ends and threads of similar colour as the net. The experiments demonstrated how a behavioural approach might be used in interpretation of a practical problem in aquaculture, and the results will be useful in the development of technology and escape mitigation strategies.

KEY WORDS: Gadus morhua · Escape · Behaviour · Biting · Net · Feed stimulant

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Cite this article as: Damsgård B, Høy E, Uglem I, Hedger RD, Izquierdo-Gomez D, Bjørn PA (2012) Net-biting and escape behaviour in farmed Atlantic cod Gadus morhua: effects of feed stimulants and net traits. Aquacult Environ Interact 3:1-9.

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