Piscivore meets pisces: interactions between grey seals and fish on the Eastern Scotian Shelf and southern Gulf of St. Lawrence

No abstracts are to be cited without prior reference to the author.

Top-down effects of upper-trophic level predators play important roles in ecosystem structure and functioning. Nevertheless, interactions between pinnipeds and their prey remain poorly understood. This uncertainty has fueled debate on the impact of seal predation on fish stocks. We show that novel combination of acoustic (Vemco Mobile Transceiver, VMT) and GPS technology can be used to determine the spatio-temporal pattern of interactions between grey seals (Halichoerus grypus) and fish species in two marine ecosystems, the Eastern Scotian Shelf and southern Gulf of St. Lawrence, Canada. During four years of study, 16 of 64 adult grey seals recorded 1,117 detections from various fish species including 17 adult Atlantic cod (Gadus morhua), 7 Atlantic salmon (Salmo salar) and one American eel (Anguilla rostrata) implanted with coded acoustics tags. An examination of the spatiotemporal pattern of these interactions suggested that none involved predation. These preliminary results provide proof-of-concept that predators fitted with VMT and GPS tags can provide information on species locations in areas where fixed receiver arrays are not present and allow new insights into the nature of predator-prey interactions in otherwise inaccessible environments.