Movement data and their application for assessing the current distribution and conservation needs of the endangered Saimaa ringed seal

Abstract

Bycatch mitigation is currently the most important issue for conservation of the Critically Endangered Saimaa ringed seal Phoca hispida saimensis found exclusively in Lake Saimaa, Finland. Two types of fishing restrictions have been established in order to reduce mortality: a ban on gillnet fishing during the most critical season (spring) to enhance pup survival and a yearround ban on the types of fishing gear most likely to cause seal mortality (e.g. certain specified fish traps, hooks baited with fish, strong-mesh gillnets, multifilament nets and trammel nets). The spatial and temporal coverage of these restrictions has not always been based entirely on the ecology and movements of the seals. The current distribution area of the population is not fully known, and this hampers the assessment of conservation needs. In this study, adult Saimaa ringed seals were tracked with GPS phone tags to estimate home ranges and movements. In addition, pup movement data from VHF telemetry studies were used to determine current breeding areas and nursing sites. The mean home ranges of both adults and pups were around 90 km2. The current distribution area of the seals covers about 70% of the surface area of Lake Saimaa (4400 km2), and the breeding area covers about 51%. The current springtime fishing restriction covers 63% of the estimated distribution area, and the restriction on fishing gear types covers 55%. This new information on the spatial ecology of Saimaa ringed seals should be used to improve efforts to conserve the species.