Impact of introduced seastars Asterias amurensison survivorship of juvenile commercial bivalvesFulvia tenuicostata
2002
Ross, DJ | Johnson, CR | Hewitt, CL
The introduction and establishment of the predatory seastar Asterias amurensis insouthern Australia is considered a major threat to benthic marine communities and commercialbivalves. The impact of A. amurensis on a soft sediment assemblage in SE Tasmania was quantified,with particular attention to effects of seastar predation on the survivorship of recently settled juvenilesof the commercial bivalve Fulvia tenuicostata. In a manipulative experiment, densities of F.tenuicostata juveniles were reduced by ca. 15 fold (from 580 to 35 m-2) in the presence of seastars atbackground densities relative to the treatment without seastars. In a feeding survey, A. amurensisexhibited preference for F. tenuicostata following settlement of the bivalve over the period fromDecember 1997 to January 1998, which comprised 80 and 50% of the seastar's stomach items in February1998 and April 1998, respectively. However, A. amurensis preferred a variety of other prey taxawhen the abundance of F. tenuicostata was low, particularly other bivalves, gastropods and the echinoidEchinocardium cordatum. This indicates that the seastar may potentially affect the abundanceof other prey taxa. The results provide further support to the hypothesis that predation by A. amurensisis largely responsible for the recent decline and subsequent rarity of large bivalves in its currentdistribution in Tasmania. The potential of seastar predation to have wider ecosystem level effectsthan the short-term direct effects reported here is a major concern.
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