Abstract
High-resolution distribution maps can help inform conservation measures for protected species; including where any impacts of proposed commercial developments overlap the range of focal species. Around Orkney, northern Scotland, UK, the harbour seal (Phoca vitulina) population has decreased by 78% over 20 years. Concern for the declining harbour seal population has led to constraints being placed on tidal energy generation developments. For this study area, telemetry data from 54 animals tagged between 2003 and 2015 were used to produce density estimation maps. Predictive habitat models using GAM-GEEs provided robust predictions in areas where telemetry data were absent, and were combined with density estimation maps, and then scaled to population levels using August terrestrial counts between 2008 and 2015, to produce harbour seal usage maps with confidence intervals around Orkney and the North coast of Scotland. The selected habitat model showed that distance from haul out, proportion of sand in seabed sediment, and annual mean power were important predictors of space use. Fine-scale usage maps can be used in consenting and licensing of anthropogenic developments to determine local abundance. When quantifying commercial impacts through changes to species distributions, usage maps can be spatially explicitly linked to individual-based models to inform predicted movement and behaviour.
Highlights
Within the context of increasing anthropogenic activities in coastal environments, understanding movement and distributions of top predators is critical to deliver effective marine spatial planning and ensure adequate management and protection[1,2,3,4]
Anthropogenic activities in the marine environment are often resolved to a fine spatio-temporal scale, and to improve efficacy in marine spatial planning it is important to use high resolution and robust maps of species distributions and habitats prioritised for conservation
The primary driver of space use was distance from haul out in the predictive habitat model; usage declined with increasing distance from haul out
Summary
Within the context of increasing anthropogenic activities in coastal environments, understanding movement and distributions of top predators is critical to deliver effective marine spatial planning and ensure adequate management and protection[1,2,3,4]. Robust estimates of space use at appropriate spatial and temporal scales are required and should include estimates of uncertainty to ensure that risks to the population can be identified and managed objectively. Anthropogenic activities in the marine environment are often resolved to a fine spatio-temporal scale (e.g. locations of marine energy leasing areas or oil and gas pipelines), and to improve efficacy in marine spatial planning it is important to use high resolution and robust maps of species distributions and habitats prioritised for conservation. Concern around the status of the population, coupled with uncertainty surrounding the risk of collisions between tidal turbines and seals, has led to constraints being placed on tidal energy generation developments in this area until more information is available on the potential risks presented to this species by tidal turbines. The declining local harbour seal population, coupled with the world’s first commercial tidal stream array (www. meygen.com) in place, makes characterisation of seal usage at a more appropriate scale for assessing individual project development essential for effective spatial management
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