Habitat-based predictions of at-sea distribution for grey and harbour seals in the British Isles:Report to BEIS, OESEA-16-76, OESEA-17-78
The United Kingdom has large populations of both grey (Halichoerus grypus) and harbour seals (Phoca vitulina), which are protected under national and international legislation. In recent years, aerial surveys have revealed region-specific changes in population dynamics for both species, ranging from...
| Summary: | The United Kingdom has large populations of both grey (Halichoerus grypus) and harbour seals (Phoca vitulina), which are protected under national and international legislation. In recent years, aerial surveys have revealed region-specific changes in population dynamics for both species, ranging from exponential increases (e.g. grey seals in the Southern North Sea) to catastrophic localised declines (e.g. harbour seals in East Scotland and Orkney). Up-to-date information on the at-sea distributions of these species is required to inform environmentally sensitive management strategies and marine spatial planning. Such distributions have been estimated using data from animal-borne telemetry tags which record and transmit tracking data, providing information on at-sea movements and haul-out behaviour. Such tags are glued to the seal’s fur and fall off during the annual moult. The Department for Business, Energy and Industrial Strategy, through their Offshore Energy Strategic Environmental Assessment (OESEA) programme, provided funding for a large-scale deployment of high resolution GPS telemetry tags on grey seals around the UK, and the subsequent analyses to generate up-to-date estimates of at-sea distribution for both seal species. To produce these estimates, a habitat modelling approach was adopted; seal tracking data were matched to a sample of the available habitat to quantify the region-specific species-environment relationships underpinning seal distribution. Spatially resolved abundance data (i.e. haulout counts) were then used to generate predictions for both species emanating from all known haulouts in the British Isles. The resulting predicted distribution maps provide estimates per species, on a 5 km x 5 km grid, of relative at-sea density for seals hauling-out in the British Isles. Three values are given for each grid cell: the mean density prediction from the habitat preference models and associated lower and upper 95% confidence intervals. For each cell, the confidence intervals provide a range of ... |
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