Changes in Pacific hake (Merluccius productus) migration patterns and juvenile growth related to the 1989 regime shift

Abstract

The response of Pacific hake (Merluccius productus) to recent changes in ocean conditions has been dramatic, with a larger proportion of the stock moving into Canadian waters in the 1990s. Additionally, after 1994, hake spawned in Canadian waters and a portion of the stock remained year round. The change in distribution corresponded with a change in growth of juvenile hake. These changes were examined in relation to upwelling and temperature. We also examined these changes in relation to changes in the abundance of euphausiids, which are the primary food supply. We propose that the 1989 regime shift differentially affected the availability of euphausiids in the northern and southern Coastal Upwelling Domain, with feeding conditions in the north improved relative to those in the south. This promoted faster growth of juveniles in the northern regions during the 1990s.