Predation of zebra mussels by crayfish

Abstract

The introduction of zebra mussels, Dreissena polymorpha (Pallas), to the Great Lakes has redirected a large amount of energy from the planktonic community to the benthic community. The direct transfer of energy from zebra mussels to other large organisms depends on the resistance of the mussels to predation. This study investigated the ability of the crayfish Orconectes propinquus (Girard) to use zebra mussels as a food source. Laboratory experiments were designed in which predator and prey sizes, as well as densities, were manipulated. When presented with zebra mussels of a range of sizes (5–20 mm), crayfish of all sizes (carapace length 1.5–2.9 cm) ate mussels ≤ 8 mm in length almost exclusively, but mussels up to 17 mm were also consumed. No significant difference in utilization of zebra mussels was found between male and female crayfish. Our findings suggest that crayfish have the potential to alter the size structure of zebra mussel populations, but that per capita mussel consumption decreased at densities > 4 crayfish/m2. Mutual interference among predators or a lack of habitat complexity may explain the reduction of mussel consumption at high densities of crayfish.