Data from: A habitat and a parasite: Adult and larval parasitic freshwater mussels impact habitat choice and predator-prey interactions of a host fish and its prey

Parasitic freshwater mussels are endangered ecosystem engineers with an
array of impacts on multiple trophic levels and life stages. While the
impacts of adult mussels on separate trophic levels have been studied, few
have directly tested how adult mussels can impact trophic interactions or
investigated the impacts of the parasitic mussel larvae (glochidia) on
such interactions. We present a lab study which mimics two stream
substrates for the endangered thick-shelled river mussel (Unio crassus):
one dominated by gravel and one by cobbles. Firstly, the preference of a
gammarid (Gammarus pulex) for mussel-dominated habitats was tested in the
presence/absence of chemical cues from the predator bullhead (Cottus
gobio). Secondly, the preference of bullhead for mussel-dominated habitats
was tested with or without glochidia infestation. Thirdly, the effect of
infestation on bullhead predation on gammarids was assessed in the
presence of adult mussels. Gammarids only significantly preferred mussel
habitats in the absence of predator cues, whereas infested bullhead tended
to prefer mussel habitats in cobble substrates. The presence of adult
mussels only significantly reduced bullhead predation on gammarids in the
gravel habitat, whereas infestation did not affect bullhead predation.
Despite gammarids not preferring mussel habitat in the presence of
predator cues, mussel beds represent valuable habitat to gammarids as
mussel presence can facilitate a reduction of predation by bullhead.
Infestation did not affect the rate of bullhead predation on gammarids but
did attract bullhead to mussel habitat in cobble substrates. Our results
suggest that mussel beds may be valuable habitat for both their host fish
and the prey of their hosts, attracting both and increasing predator-prey
interactions. This study highlights the cross-trophic mechanisms by which
multiple life stages of parasitic mussels can impact the interactions of
their surrounding benthic community, underscoring their importance as
ecosystem engineers.