Abstract
Fish were observed reacting to moving net panels in tank experiments and in trawl gears towed at sea. Two typical response behaviours of haddock, saithe, mackerel, cod and flatfish to the gear are described as optomotor response and erratic response. These two responses were analysed from TV recordings of the reacting fish and are characterised by time sequences of four parameters: swimming speed, acceleration, angular velocity and distance to the net panel. When fish display stable swimming near the net mouth as in an optomotor response, variations of swimming speed, acceleration and angular velocity are relatively low and regular in their amplitude and period. The erratic response is characterised by large variations in velocity, acceleration and angular velocity and only distance to the towed netting panel, which is positive inside and negative outside, shows progressive change. It is suggested that the fish’s process of deciding between optomotor or erratic response to the gear is based on predictable parameters that describe the stimulus like sound, light level, visibility range and object contrast, combined with the limits describing the abilities of the fish to see, hear and move. The behaviour of the observed parameters suggest that the balance between these factors in a model predicting the outcome might benefit from a form of chaos theory.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.