Caspian Seal Transitory Migration and Feeding Area IMMA

Criterion A – Species or Population Vulnerability

The Caspian seal is listed as Endangered by IUCN (Goodman & Dmitrieva 2016), and in the Red lists of all 5 littoral states (Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan). Since it is landlocked within the Caspian Sea it has no possibility to migrate to alternate areas, and therefore is entirely dependent on the Caspian environment. The IMMA encompasses the primary areas used by Caspian seals for feeding and seasonal migration throughout the Caspian Sea basin, connecting key areas used for breeding, moulting, hauling out and foraging.

Criterion C: Key Life Cycle Activities

Sub-criterion C2: Feeding Areas

Satellite telemetry deployments between 2009 and 2018, and spatial modelling of the data demonstrate consistent foraging activity throughout the IMMA area (Dmitrieva 2013; Dmitrieva et al. 2016; Dmitrieva et al. unpublished data). Areas which show seasonally increased rates of foraging activity from spring through autumn in the north and mid-Caspian basins include the mouth of the Volga delta, an area of steeply sloping bathymetry on an arc between the Mangistau peninsula (Kazakhstan) and Chechen Island (Dagestan, Russia), offshore from the city of Derbent (Dagestan Russia), and waters north of the Absheron peninsula (Azerbaijan).

For animals migrating into the southern basin during summer months, most foraging activity is concentrated around areas of steeply sloping bathymetry, particularly to the west of Ogurjaly (Ogurchinskiy) Island (Turkmenistan), but there is large individual variation, and seals were observed to use a wide range of water depths, and distances from shore. Smaller numbers of tagged seals were observed to use waters along the Iranian coast, however, habitat use models based on environmental variables predict a high probability of seal foraging in this area. This is supported by numerous reports of seal presence in the area throughout the year from visual sightings, and regular entanglements of seals in gear from nearshore fisheries in Iran (e.g. Sanaee et al. 2020). The seal presence observed in the south during the winter may reflect non-breeding animals remaining to exploit the higher productivity waters in colder months. The telemetry studies primarily targeted breeding adult animals, and therefore juveniles and other non-breeding individuals may be underrepresented in the telemetry data.

There is high individual variation in foraging behaviour, but Dmitrieva et al. (2016; unpublished data) identified 3 classes of behaviour that may reflect foraging specialisations for different types of habitat or prey. ‘Shallow diving seals’ only exhibited dives to depths less than 10m, ‘intermediate divers’ did not dive deeper than 25m, while ‘deep divers’ dived to depths of up to 200m and greater. Seals specializing in these classes of behaviour were spatially segregated, with shallow divers (approximately 40% of tagged animals) remaining in the north Caspian (particularly around the Volga delta) throughout the summer, intermediate divers favouring the transition areas between the north and mid basins, and deep divers migrating into the mid and southern basins. In the mid-basin elevated rates of foraging activity were often associated with steeply sloping bathymetry and occurred in waters around and west of the Gulf of Kenderli. During the winter breeding season tagged seals were observed to make return foraging trips from the ice field to more than 400km south, and these trips could last up to a month. This may reflect low prey availability due to seasonally decreased primary productivity in the north. The small body size of Caspian seals means that blubber reserves accumulated during the summer are not sufficient to sustain individuals throughout the whole breeding period without supplementary feeding.

Sub-criterion C3: Migration Routes

More than 99% of the Caspian seal population breeds on the ice field which forms in the shallow northern basin from December to March. The seals then moult on sand banks and areas of reeds in the north after the spring ice melt. From early April to mid-May, moulted seals disperse to summer foraging areas in the northern, mid and southern basins which is the habitat included in this IMMA. In satellite telemetry studies (Dmitrieva et al. 2016, Dmitrieva et al. unpublished data), around 60% of tagged seals migrated into the mid and southern basins, mainly following routes along the east and west coasts of the mid Caspian basin between the coast and 200m isobath. However, multiple satellite tracks were also observed for animals taking direct lines of movement across the deep basins.