Marine habitat use by grey seals in Brittany: application to the Marine National Park of the Iroise Sea

The grey seal Halichoerus grypus is a key species living in the planned Marine National Park of the Iroise Sea, at the western point of Brittany. A telemetry study was set up in order to track movements and behaviour at sea of six grey seals, for a better understanding of the foraging behaviour of the species in Brittany. The use of Satellite Relay Data Loggers (SRDL, Sea Mammal Research Unit, UK) showed extensive individual variability in movements at sea and foraging strategies. All seals used distinct foraging areas; some of them travelled long distances at sea for feeding while others foraged in coastal habitats. Dive forms and depths suggested that the seals can forage during different types of trips at sea, including in the vicinity of their haul-out sites. However their potential foraging areas are widely dispersed and greatly exceed the limits of the planned protected area. The impact of the predation of the seals on fish resources within the Marine National Park is therefore expected to be limited. We suggest that fish resources as well as interactions between seals and fisheries should be managed at a broader scale.