Distribution and migration of saithe (Pollachius virens) around Iceland inferred from mark-recapture studies

Knowledge of the distribution and migration of populations is necessary to identify and conserve stock components and therefore genetic variability. Compared with other gadoid species, little is known about the life history of saithe (Pollachius virens) (known as pollock in the Northwest Atlantic) or its stock components. About 15 800 saithe were tagged near Iceland from 2000 to 2004 to estimate population parameters, to describe saithe dynamics on the Icelandic shelf, and to monitor long-distance migrations, should they occur. A multiplicative model was used to standardize fishing effort to describe the distribution of the tagged population, based on tag returns from the fishery. Saithe have a high affinity to their tagging area, but move considerably within that area. Because of variability in fishing effort among areas, tagged fish exhibit different area-specific catchabilities. The results also indicate seasonal offshore- inshore migrations during summer and variability in migratory routes among different tagging areas related to affinities to different feeding grounds. This could indicate a more complex stock structure than previously thought. Finally, results to date do not indicate large-scale emigration of saithe from Icelandic fishing grounds.