Abstract
reventing 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 in -
cluded 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.
Gadus morhua · Escape · Behaviour · Biting · Net · Feed stimulant
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 in -
cluded 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.
Gadus morhua · Escape · Behaviour · Biting · Net · Feed stimulant
