Use constraints: The data and resulting data products (tables, figures and maps) available on the indicator web page can be used freely given that the source is cited. The indicator should be cited as following: HELCOM (2018) Population trends and abundance of seals - Ringed seal. HELCOM core indicator report. Online. [Date Viewed], [Web link].

The indicator is based on line transect surveys of hauled out ringed seals on ice during the moulting period in the latter half of April. Such surveys have been carried out annually in the Bothnian Bay. Only sporadic surveys have been carried out in the Archipelago Sea , the Gulf of Finland and Estonian coastal waters due to limited or no sea ice. Surveys are carried out from high-winged aircrafts, where all seals within the transect are photographed for later enumeration on the photos. A minumum of 13% of the ice area is covered. Greater effort only marginally reduce variances. Surveys should be carried out during similar conditions each year to get compatible results. In two years (2014 and 2015) ice conditions deteriorated early in the Bothnian Bay, which is why these years have to be treated separately in trend analyses. The reason why much higher numbers hauled out in 2014 and 2015 was that subadult animals that normally are chased away by the adults entered into the breeding ice when the social structure of the habitat collapsed. Nevertheless, these high numbers show that numbers of seals in the Bothnian Bay amount to about 20 000 seals . The criteria for GES are that numbers of seals must exceed 10 000 animals and that the population growth rate must exceed 7% per year. Survey data are available from the Gulf of Finland and Estonian coastal waters from 1996. In the Gulf of Finland numbers of seals have decreased from 300 in 1996 to 100 in 2015. For Estonia no increase is seen since 1996, but possibly a decrease.

The calculations have been carried out by Lead Country Sweden based on survey data. For the Archipelago Sea, the Gulf of Finland and Estonian coastal waters indicator reference is given to data published in the references provided in the Core indicator report (see link below).

Additional information:

http://www.helcom.fi/baltic-sea-trends/indicators/population-trends-and-abundance-of-seals/