A review of the situation for the Baltic Sea harbour porpoise and recommendations for conservation measures
Ida Carlen and Mark Simmonds
International Whaling Commission
The Baltic Sea harbour porpoise is listed by IUCN and HELCOM as critically endangered. Today its geographical range is significantly smaller than its historical one, and there are only a few hundred animals left. While pollution and disturbance through underwater noise may be contributing to the population failing to recover, bycatch is the one acute threat causing direct mortalities in significant numbers. Given the small size of the population, the sex ratio and age distribution and the proportion of females that are potentially infertile due to high contaminant load, there may be less than 100 fertile females remaining in the Baltic Proper. Losing even one of those females could have a devastating effect on the ability of the population to recover or even stay stable.
Hence, to allow this critically endangered population to recover, bycatch must be reduced to an absolute minimum, ideally to zero. However, to date, initiatives from Member States to minimize bycatch are very limited and there are currently no closures of areas for the purpose of protecting the Baltic Sea harbour porpoise. While Sweden designated the main part of the porpoise breeding area in the central Baltic Proper as a Natura 2000 site in December 2016, the long and slow process for Member States to agree on joint measures for nature conservation purposes under the Common Fisheries Policy (CFP) is currently risking the survival of the population.
We therefore recommend for the following conservation measures to be taken:
- close all set net fisheries in Marine Protected Areas (MPAs) designated specifically for the Baltic Sea harbour porpoise;
- Identify further areas of high bycatch risk and take action to close set net fisheries in those areas as well;
- use pingers or other bycatch mitigation measures, such as alternative gear, in the entire Baltic Sea; and
- ensure adequate prey availability by limiting large scale fishing/trawling in areas of high importance to the Baltic Sea harbour porpoise population.