Spatial Scales of Movement in Northeast Atlantic Coastal Cod

Abstract

The movement patterns of released hatchery-reared fish determine the geographical scale at which a population may be enhanced, while the movement patterns of wild fish affect the management strategies of wild populations. This article investigates (1) if movement patterns differ between hatchery reared and wild cod, and (2) if the movement patterns of coastal cod differ between regions. The results from a large mark-recapture experiment in northern Norway showed that displacement distances (DD) for both wild and hatchery-reared fish were highly skewed. The frequency distribution of DD for wild cod was well described by a log-normal distribution. While reared cod that were released at a small size (< 27 cm in length) and young age (< 1 year of age) had similar movement patterns to wild cod of similar size, reared cod that were larger and older at release dispersed rapidly after release. The frequency of long-distance migrations (DD > 50 km) for larger reared cod was similar, however, to that of wild cod. Fitting log-normal distributions to published mark-recapture data revealed that there was a latitudinal trend, with longer displacement distances in the north than in the south. Cod released in coastal bank areas and offshore island groups also had longer displacement distances than cod released at the Norwegian coast.