AEI 3:33-49 (2012)  -  doi:10.3354/aei00049

Extent and ecological importance of escape through spawning in sea-cages for Atlantic cod

Ingebrigt Uglem1,*, Øyvind Knutsen2, Olav Sigurd Kjesbu3, Øyvind J. Hansen4, Jarle Mork5, Pål Arne Bjørn3,4, Rebekka Varne5, Rune Nilsen3,4, Ingrid Ellingsen2, Tim Dempster6,7

1Norwegian Institute of Nature Research, Tungasletta 2, 7485 Trondheim, Norway
2SINTEF Fisheries and Aquaculture, PO Box 4762 Sluppen, 7465 Trondheim, Norway
3Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway
4NOFIMA Marin, Muninbakken 9-13, PO Box 6122, 9291 Tromsø, Norway
5Trondheim Biological Station, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway
6Sustainable Aquaculture Laboratory − Temperate and Tropical (SALTT), Department of Zoology, University of Melbourne,
3010 Victoria, Australia
7Centre for Research-based Innovation in Aquaculture Technology (CREATE), SINTEF Fisheries and Aquaculture, PO Box 4762 Sluppen, 7465 Trondheim, Norway

ABSTRACT: The culture of certain fish species to sizes at which they can reproduce has led to the escape of fertilised eggs or ‘escape through spawning’. To investigate the extent and ecological importance of spawning in sea-cages for Atlantic cod Gadus morhua (L.), we (1) evaluated the extent, frequency and timing of spawning in cod culture; (2) analysed the quality of eggs released from farms in terms of variation in fatty acids; (3) modelled the distribution of eggs and larvae from a commercial cod culture site; and (4) predicted the post-escape survival of eggs through summarizing existing knowledge on survival rates of different life stages. Collectively, our results indicate that cod farming has the potential to produce large amounts of eggs and larvae through spawning in cages, with numbers of eggs spawned being 4 to 5 times higher in the second than in the first year. Our scenarios suggest that a typical sea-cage with 60000 fish may produce 1.4 to 21 tons of 3 yr old first generation farmed cod through spawning in sea-cages. The quality of escaped eggs and larvae is likely to be sufficient for larvae to survive until the first feeding, while survival until adulthood, though difficult to predict, may be high under favourable conditions. Simulations indicate that eggs and larvae from farms may mix with those of wild fish during the spawning season, and thus experience comparable larval environments. However, several implementable management measures exist that will diminish the extent of egg escape in future cod farming.


KEY WORDS: Atlantic cod · Gadus morhua · Aquaculture · Escape · Spawning in farms


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Cite this article as: Uglem I, Knutsen Ø, Kjesbu OS, Hansen ØJ and others (2012) Extent and ecological importance of escape through spawning in sea-cages for Atlantic cod. Aquacult Environ Interact 3:33-49

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