Benthic Invertebrates of the Eastern Bering Sea: A Synopsis of the Life History and Ecology of the Sea Star Asterias Amurensis

摘要

Invertebrates constitute an important element in the benthic ecology on the eastern Bering Sea (EBS) continental shelf, playing an important part in the food web supporting not only the benthos, but commercially important demersal fish species as well. The asteroid species Asterias amurensis represents a major portion of the benthic invertebrate biomass over most of the shelf, but it is especially prevalent in the inshore domain out to about the 50 m isobath. The species is also native to coastal areas of the northwestern Pacific, including the Tatar Strait, eastern and western Sea of Japan, and the east coast of Japan. It is a predator upon numerous shelled mollusk species, as well as other invertebrates of limited motility, and is also an opportunistic scavenger. Asteroids appear to have few predators, and in food webs A. amurensis is a terminal consumer. It therefore competes with some commercially important demersal fish species, as well as commercially important invertebrates such as the king crab Paralithodes camtschaticus. A possible mitigating circumstance in its ecological role is the large contribution to secondary production constituted by the release of potentially millions of eggs by each spawning female during the annual reproductive cycle. With its lack of susceptibility to predation, the species has proven a major threat to the ecological balance in areas where it is not native, but has been inadvertently introduced by such means as release of planktonic larvae in ballast water jettisoned by foreign ships in port; for example, in some coastal waters of southeastern Australia and Tasmania. Here native species of bivalves have proven especially vulnerable to the predator. This report presents a synopsis of the current knowledge of the life history and ecology of the species, including details of its distribution in the EBS based on maps showing abundance data from the annual bottom trawl surveys of fish and invertebrates on the EBS shelf conducted from 1983 to 2013 by the National Oceanic and Atmospheric Administration, Alaska Fisheries Science Center, Resource Assessment and Conservation Engineering Division. The biological characterizations are from the available published literature and are based on observations of populations in the native or invaded ranges of the species. This is the second in a series of such Technical Memoranda published to provide information on invertebrate species significant to the ecology of commercially important demersal and benthic fish and invertebrates of the EBS.