Long-Term Changes in Gulf of Alaska Marine Forage Species 1953-1998

Summary:
Declines of apex predator populations (murres, kittiwakes, harbor seals, and Steller sea lion) have occurred in the Gulf of Alaska (GOA) since the 1970s. Changes in composition and abundance of forage species may be related to the decline of these predator populations and their chronic low population levels. A trophic regime shift resulting from a climatic forcing event in the last half of 1970s is suggested as the driving mechanism for these observed trends. We present data, collected in a similar manner, over widely dispersed regions of the Gulf of Alaska. These data show massive reorganization of the marine ecosystem following the extreme environmental change, as evidenced in long-term (1953-1998) small-mesh trawl surveys. Nearly 10,000 individual sampling tows are in the current project database. Recent analysis of the 1996-1998 survey data has indicated that the groundfish-dominant trophic structure still exists with no signs of reversal. Thus, the current system exhibits a high degree of stability. Long-term monitoring is needed to determine what drives and maintains these GOA marine ecosystem changes, particularly the effects on apex predators.


Principal Investigators:
Paul J. Anderson, National Marine Fisheries Service, Kodiak, AK
John F. Piatt, U.S. Geological Survey, Biological Resources Division, Anchorage, AK
James E. Blackburn, Alaska Department of Fish and Game, Kodiak, AK
William R. Bechtol, Alaska Department of Fish and Game, Homer, AK
Tracey Gotthardt, U.S. Fish and Wildlife Service, Migratory Bird Management, Anchorage, AK