Daniel Esler
W. Sean Boyd
Tyler Lewis
2007
<p><span>Recent studies have documented strong, top-down predation effects of sea ducks on mussel populations in rocky intertidal communities. However, the impact of these gregarious predators in soft-bottom communities has been largely unexplored. We evaluated effects of predation by wintering surf scoters </span><i>Melanitta perspicillata</i><span> and white-winged scoters </span><i>M. fusca</i><span> on clam populations in soft-bottom intertidal habitats of the Strait of Georgia, British Columbia. Specifically, we documented spatial and temporal variation in clam density (clams m</span><span>–2</span><span>), scoter diet composition, and the consequences of scoter predation on clam abundance. Of the 3 most numerous clams, Manila clams </span><i>Venerupis philippinarum</i><span> and varnish clams </span><i>Nuttallia obscurata</i><span> were the primary prey items of both scoter species, while clams of the genus </span><i>Macoma</i><span> were rarely consumed by scoters. Between scoter arrival in the fall and departure in the spring, Manila clams decreased in density at most sample sites, while varnish clam densities did not change or declined slightly. Our estimates of numbers of clams consumed by scoters accounted for most of the observed declines in combined abundance of Manila and varnish clams, despite the presence of numerous other vertebrate and invertebrate species known to consume clams. For </span><i>Macoma</i><span> spp., we detected an over-winter increase in density, presumably due to growth of clams too small to be retained by our sieve (<5 mm) during fall sampling, in addition to the lack of predation pressure by scoters. These results illustrate the strong predation potential of scoters in soft-bottom intertidal habitats, as well as their potentially important role in shaping community structure.</span></p>
application/pdf
10.3354/meps329131
en
Inter-Research
Effects of predation by sea ducks on clam abundance in soft-bottom intertidal habitats
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