Long-term stability and change in the commercial groundfish longline fishing grounds of the northwest Atlantic

The fishing grounds in the northwest Atlantic Ocean that were exploited by commercial groundfish longline boats in the 1880s, in about 1940 and in 1990 are compared and examined for evidence of changes in fish distributions over multi-decadal time scales. In general, the grounds fished were notably similar at the three times, the halibut grounds being particularly stable. Moreover, most of the changes detected can be attributed to developments in markets, regulations or similar human concerns. However, the known withdrawal of haddock from the former limits of its range is seen as a change in the areas fished for that species. There is also some evidence for shorter-term changes in cod abundance on grounds near the entrance to the Gulf of St. Lawrence. It is suggested that the general stability in the grounds fished is consistent with the potential productivity of the resources having also remained stable, despite the great increase in fishing effort during the last century. The common assumption of stability in productivity that is implicit in most stock assessments is therefore supported, except for those stocks that are near the limits of their species' range.