The Baltic Sea harbour porpoise population is classified as critically endangered by the International Union for Conservation of Nature, IUCN. After a significant decrease in numbers from the 1960’s and forward, in the beginning of the 21^st century no one knew how many animals were left in the Baltic, despite surveys using different methods. Also, there was no knowledge on the distribution of animals in the Baltic. The only information came from reported observations collected by different national bodies and collected at the HELCOM harbour porpoise database.

Reported observations occur along the coasts, since this is where most people spend their time. Without information on where the largest part of the population is, it is very difficult to take effective conservation measures. To gain more information, authorities and scientists from all EU countries around the Baltic Sea decided to start a common project using new acoustic methods to survey the distribution and abundance of harbour porpoises in the Baltic Sea. The project, which started in 2010, was named SAMBAH, Static Acoustic Monitoring for the Baltic Sea Harbour Porpoise.

SAMBAH estimated the number of harbour porpoises left in the Baltic Proper population to approximately 500 animals. The project could also show what areas are most important to porpoises during different seasons, and could thereby also show where the Baltic Sea harbour porpoise reproduce. This was previously completely unknown, and this new knowledge was instrumental in designating relevant areas for protection of porpoises. Based on the results from SAMBAH, in December 2016 the Swedish government designated a large Natura 2000 area south of Gotland

The area is more than 1 million hectares, and includes most of the area where the Baltic Proper harbour porpoises are thought to give birth to their calves and mate in the summer. To protect the porpoises here is very important to give the population a chance to recover. At CCB, we are now working together with authorities and stakeholders to look at suitable conservation measures for this area. In this work, we need your help to convince the politicians that protecting the Baltic Proper harbour porpoise is important, so that they make the right decision about the management of this new Natura 2000 area.

The most severe threat to harbour porpoises is bycatch in fisheries. Because porpoises need to get to the surface to breathe, they drown if they get caught in a fishing net. The nets with the highest risk if bycatch are large mesh nets used to catch for example cod and flatfish, as well as salmon nets. Porpoises rarely get caught in trawls or other active gear, so set nets are the primary threat. To avoid bycatch some measures could be

• Decrease fishing effort with set nets in important areas
• Switch set nets for alternative gear such as pots or traps
• Use pingers on any set nets used. Pingers emit sound signals scaring the porpoises or warning them of the presence of nets

There are problems with all of these methods and different methods may be suitable in different areas, so it is important to have a good dialogue with stakeholders to adapt measures.

Because harbour porpoises use echolocation to orientate themselves, find prey and communicate, they are sensitive to underwater noise. The level of noise in the oceans has increased significantly during the last decades, with noise from shipping, dredging, construction, leisure boats and jet skis. With increased noise, porpoises have problems hearing the echoes from their own echolocation clicks, which makes it harder for them to find prey. It also becomes more difficult for porpoises to hear eachother. Their high frequency sounds travel only short distances under water, and with increased noise levels it becomes even shorter. This can cause calves to loose their mothers, or females and males not finding eachother when it is time to mate. To decrease the impact of underwater noise in especially sensitive areas we can

• Restrict shipping traffic
• Move shipping routes
• Introduce speed limits for, or completely ban leisure boats
• Prohibit construction of for example wind farms, or enforce strict rules on how construction must be carried out