BB1 - Abundance and distribution of seals (M3)

Atlantic grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) are both regularly found in OSPAR Regions I, II and III. As higher predators, seals can be used as an indicator to reflect the state of the marine ecosystem. Assessment of seal abundance and distribution aims to determine if populations of both species are in a healthy state, with no long-term decrease in population size, beyond natural variability. Historically, populations have declined due to anthropogenic influences. Seal abundance and distribution are influenced by many factors, such as disease, competition with other species, changes in the distribution and abundance of prey, disturbance and interactions with fisheries. Seals were hunted into the 20th century, and as a result have disappeared entirely in some areas, but are now protected in most areas of Europe. Future changes in distribution or declines in abundance may signal that populations are no longer in a healthy state. Further studies would then be needed to establish the cause of these changes and to determine whether management measures are required.

The monitoring required for seal indicator M3 is on the numbers and location of individuals on land at colonies or haulout sites throughout OSPAR regions I, II and III. Surveys are usually conducted from the air, but may also be conducted from land or by boat. In most areas, aerial surveyors take photographs of the haul-out sites and animals are later counted from the images. There are two periods during the year when most grey and harbour seal surveys take place: breeding (pupping) and moulting. Harbour seals give birth to pups in early summer and moult after breeding in late summer. Grey seals pup in the autumn or winter and moult in early spring. The frequency of surveys during these periods varies across OSPAR Contracting Parties due to differences in the total number of resident animals, funding, geography and historical development of the monitoring programmes. Repeated surveys of both grey and harbour seals throughout the year are not economically feasible and Contracting Parties use population censuses in one or perhaps two seasons of the year.

Which other countries are involved in practical implementation of this monitoring programme, and what is the degree of cooperation.

Agreed data collection methods
DE, DK, FR, IE, IS, NL, NO, SE, UK

[Monitoring Purpose]