Attachment and Shell Integrity Affects the Vulnerability of Zebra Mussels (Dreissena polymorpha) to Predation

ABSTRACT

We investigated the relationship between prey condition and predation vulnerability in the zebra mussel (Dreissena polymorpha). In aquarium experiments with rusty crayfish (Orconectes rusticus), a known predator of the zebra mussel, both removal of the zebra mussels from their substrata and damage to their shells significantly increased their vulnerability to predation. This result was corroborated in open-water trials in Douglas Lake, Michigan, USA. The effect of shell damage on predation of the mussels was less pronounced in the lake than in the laboratory, probably owing to the presence in the lake of alternative prey items for predators. In the lake trials, there was a significant negative correlation between predation and the distance the samples were set from the shoreline. Although zebra mussels can be important food items for molluscivore predators, their vulnerability to predators which use chemical cues such as rusty crayfish appears to be directly related to the integrity of the mussel shell and/or their byssus (attachment) threads.