MEYER, J* J; BYERS, J E; University of New Hampshire; University of New Hampshire: Sublethal predation facilitates lethal predation: consequences of siphon cropping on two intertidal bivlave species

In soft-sediment marine communities, fishes often crop the extended feeding siphons of buried clams. This potentially causes clams to reduce their burial depth thereby enhancing their susceptibility to excavating lethal predators. To examine this linkage experimentally, we simulated siphon-cropping of the confamilial clams, Protothaca staminea and Venerupis philippinarum, by removing the top 40% of siphons, which in turn caused each species to burrow 33-50% shallower than conspecifics with intact siphons. To determine the subsequent consequences of reduced burial depth, we exposed cropped and intact clams of each species to natural levels of predation in the field. Because of a naturally longer siphon, Protothaca, even after cropping, remained at relatively safe burial depths and sustained similar mortality rates between intact and cropped individuals. In contrast, siphon cropping nearly doubled the mortality rate of Venerupis compared to intact conspecifics. Thus, while sublethal predation facilitates lethal predation, this relationship depends on specific life history characteristics, even among ecologically similar species.