Meeting Abstract
This study focused on predator prey interactions of the crab Pugettia gracilis and sea stars of the genus Leptasterias and two herbivorous snails, Lacuna vincta and L. variegata that graze on macroalgae and microalgae that foul eelgrass. Habitat differences can change foraging behavior of predators and either aid or hinder efficiency of predation. We examined the vulnerability of Lacuna in eelgrass and macroalgal habitats to predation by the crab and sea star. We determined the maximum feeding rate of each predator on each species of snail, and tested whether there was size specific predation or if predators had a preference or potential for greater impact on each species of prey. Finally, we tested whether feeding efficiency differed in the two habitat types. In no choice laboratory experiments the crab ate significantly more L. variegata (1.4/hr) than the sea star (0.7/hr) and both predators had the same feeding rate on L. vincta (crab – 0.9/hr, star 0.6/hr). When given a choice, the crab preferred L. variegata and the sea star showed no preference. Neither predator was size selective and the size of the predator did not impact feeding rate. The vulnerability of snails in the two habitats was tested with mesocosm experiments. Because of low recovery of snails in controls, we were unable to detect significant differences between the predators in the two habitats. Results suggest feeding rates for the sea star were half those in laboratory. The crab seemed to prefer L. variegata. Mesocosm design must be refined to facilitate recovery of snails and more replicates are needed to determine if there are significant differences in predation in the two habitats.
