Recent reports from the north and south of the Bay of thousands of fresh, washed-up Thin-ribbed cockle shells (Fulvia tenuicostata) raise concerns about the impact of Northern Pacific Seastars (Asterias amurensis) on this species; particularly as most shells were less than quarter the typical adult size of around 40mm.
Tasmanian research – Impact of introduced seastars on survivorship of juvenile bivalves Fulvia tenuicostata (Ross, Johnson & Hewitt, 2002) found bivalve molluscs were the main prey of the pest seastars. Most bivalves live in the sediments and have two siphons that reach to the sediment surface to respire, feed, excrete and reproduce. Because of their short siphons Fulvia tenuicostata, Venerupis anomala, Corbula gibba and Timoclea cardoides live just below the sediment surface and are easy prey for seastars.
A. amurenis were first recorded in Tassie in 1986 and by the late 1990’s were the dominant invertebrate predator in the Derwent estuary. Surveys between November 1997 and November 1998 found juvenile bivalves were the main diet of A. amurensis, raising concerns that over-predation of juveniles will ultimately reduce the number of breeding-age bivalves. How much do we know of the impact of A. amurensis on Port Phillip Bay’s bivalve populations? Which regions are critical habitat for bivalves; and which native species rely on them for survival?
