Catch me if you can: archival tagging studies can help assess changesin the accessibility of Atlantic cod (Gadus morhua) to trawl gears

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Knowledge of fish behaviour can influence the way that landings or survey data are interpreted in several ways. Fish may be more or less available to survey gear in a particular region, a variable dependent upon seasonal migrations (Harden-Jones, 1968). In addition, fish may be more or less accessible to fishing gears, a variable dependent upon the behaviour of fish in relation to topography and bathymetry (Harden-Jones, 1968 ; Godø, 1994). Finally, fish may be more or less vulnerable to capture by survey gears, a variable dependent upon gear efficiency and sampling effort (Godø, 1994). However, studying and understanding fish behaviour, particularly in the natural environment, is difficult because individuals may not be easily followed, particularly for long periods of time (Metcalfe & Arnold, 1997). Telemetry and archival tags, the performance of which has advanced considerably in recent years, now make observations of the behaviour of large fishes relatively routine.