Publication Abstract

Rhythm and repeatability: analysis of stereotypical behaviour patterns of NE Atlantic cod

D.Righton and K. Michalsen

The vertical movements of fishes have profound effects on their detectability and catchability, yet knowledge of fish behaviour is under-utilised when assessment surveys are planned and interpreted. Data storage tags (DSTs) were used to gather field-observations of the vertical movements of individual cod in the Barents and North Seas. The vertical movements of each individual were analysed using periodogram and pattern analysis to determine the rhythmicity (its occurrence and frequency) of the vertical movements. For cod of both regions, strong diurnal patterns existed in vertical movement behaviour at certain times of the year. At other times, rhythmicity was absent. Cod of both regions also showed repeat (and stereotypical) vertical movement patterns related to feeding, migrating and spawning behaviours. Our analyses demonstrate that cod show systematic variation in vertical movement behaviour that provides fisheries assessment scientists with information relevant to the interpretation of catch and effort data.

Reference:

D.Righton*  and K. Michalsen (2003) Rhythm and repeatability: analysis of stereotypical behaviour patterns of NE Atlantic cod. ICES Symposium on behaviour of fish in exploited ecosystems