Predation by the invasive American signal crayfish, Pacifastacus leniusculus Dana, on the invasive zebra mussel, Dreissena polymorpha Pallas: the potential for control and facilitation |
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Authors: | Philine S E zu Ermgassen and David C Aldridge |
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Institution: | (1) Aquatic Ecology Group, Department of Zoology, University of Cambridge, Cambridge, CB2 3EJ, UK |
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Abstract: | Non-indigenous crayfish often have major ecological impacts on invaded water bodies, and have contributed to the decline of
native crayfish species throughout Europe. The American signal crayfish, Pacifastacus leniusculus, is the most widespread invasive crayfish in Great Britain, where the zebra mussel, Dreissena polymorpha, is similarly an invasive pest species. The potential for the American signal crayfish to regulate zebra mussel populations
was investigated through a series of laboratory experiments. Crayfish were found to be highly size selective, consuming significantly
more of the smallest size class of zebra mussels offered (7–12 mm), over medium (16–21 mm) and large (25–30 mm). Crayfish
feeding rate on zebra mussels was not altered when mussels were presented clumped together in natural druses compared with
mussels in a disassembled druse. Crayfish spent significantly more time foraging when mussels were unattached, and a greater
proportion of attacks were on medium and large than on small mussels (83% of attacks were on medium and large mussels when
unattached as opposed to 47% when on druses). Individual crayfish feeding rate decreased significantly at densities of > ~5
crayfish m−2. Signal crayfish are, therefore, unlikely to be able to significantly impact established populations of zebra mussels in
the wild, although zebra mussels have the potential to provide crayfish with a substantial food source. |
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