Documentation of multiple species of marine fish trapped in Atlantic salmon sea-cages in Norway

The production of salmonids in sea-cages has been developed for monoculture of the target species. However, we show here for the first time, that wild fish may enter sea-cages used for farming of Atlantic salmon (Salmo salar L.) in Norway, out-grow the mesh size, and thereafter become permanently tr...

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Bibliographic Details
Published in:Aquatic Living Resources
Main Authors: Fjelldal Per Gunnar, Solberg Monica F., Glover Kevin A., Folkedal Ole, Nilsson Jonatan, Finn Roderick Nigel, Hansen Tom Johnny
Format: Article in Journal/Newspaper
Language:English
Published: EDP Sciences 2018
Subjects:
ecology
life cycle
gadoids
fjord
coast
finfish mariculture
polyculture
environment
bycatch
Aquaculture. Fisheries. Angling
SH1-691
Hake
Norway
Anguilla anguilla
Atlantic salmon
European eel
Gadus morhua
Salmo salar
Online Access:https://doi.org/10.1051/alr/2018020
https://doaj.org/article/24af159cc48f4b3989594bf295c427cc
Description
Summary:The production of salmonids in sea-cages has been developed for monoculture of the target species. However, we show here for the first time, that wild fish may enter sea-cages used for farming of Atlantic salmon (Salmo salar L.) in Norway, out-grow the mesh size, and thereafter become permanently trapped. Within seven different sea-cages located in western Norway, eight different species of wild fish were identified; European eel (Anguilla anguilla), sea trout (Salmo trutta L.), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), pollack (Pollachius pollachius), hake (Merluccius merluccius) and whiting (Merlangius merlangus). In the two most extreme cases, a 5 × 5 × 7 m cage with 311 farmed salmon (903 g) also contained 542 whiting (79 g), 77 haddock (43 g), and 5 cod (26 g), and a 12 × 12 × 15 m cage with 1695 farmed salmon (559 g) also contained 1196 haddock (35 g), 1115 whiting (31 g), 46 cod (23 g), 23 saithe (48 g), 15 pollock (22 g), 5 sea trout (54 g), and 2 hake (29 g). The present study thus demonstrates that aquaculture cages designed for monoculture may attract and effectively ‘trap’ wild fish. We did not investigate the frequency of this occurrence, and the ecological significance of these observations remains unclear. However, with the ever-increasing number of sea-cages used for global aquaculture, this is clearly a topic for further research.

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