| Summary: | The demise of Britain’s only native crayfish (Austropotamobius pallipes
(Lereboullet)) has prompted conservation-led translocations to safe isolated
stillwaters (Ark sites). Many translocations represent introductions rather than
re-stocking; hence it is important to ensure that there will not be a detrimental impact
on communities already present. Current knowledge is insufficient to predict likely
effects, although gut contents analyses suggest that A. pallipes is
omnivorous and exhibits ontogenic diet shifts. A mesocosm study was conducted with the aim
to first, determine community impacts of introducing A. pallipes on the
benthic invertebrate community, and second investigate if impacts vary with crayfish
life-stage. All crayfish life-stages strongly reduced shredder and grazer abundance,
particularly thin-shelled Lymnaea snails. The small snail Physa
fontinalis was preferentially consumed by juveniles, perhaps reflecting
different prey-handling ability. Adults showed greater reliance on terrestrially derived
detritus compared to juveniles. There were limited effects on other trophic levels,
although by reducing shredders that process basal resources, crayfish impacts may be felt
through the community in the long-term.
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