Pandalid shrimp as indicators of ecosystem regime shift

Abstract

Pandalid shrimp are important components of the cold-regime boreal marine ecosystem in the Gulf of Alaska. Declines in abundance of several pandalid species occurred quickly after 1977 when an abrupt climate change caused water column warming. Shrimp trawl surveys conducted from 1953 to 1999 were used to describe how species composition changed relative to environmental parameters. Proportions of shrimp in survey catches were found to be negatively correlated (r = -0.72) with the water column temperature anomaly. Pandalid shrimp species which occupied inshore and typically shallower water declined to near extinction, while offshore and deep-water shrimp species maintained low population levels. Possible mechanisms responsible for this decline and their replacement by other species are discussed. Climate change as manifested by changes in water column temperature has an immediate effect on lower trophic levels of boreal marine ecosystems and rapid pandalid shrimp population changes are one of the first indicators that a community regime shift is underway.