Assessing the distribution and vulnerability of a seabird community at sea to inform conservation and management

Abstract

Seabirds are an apex predator in marine ecosystems and can be important bio-indicators for informing wider marine conservation and management. They face many threats from anthropogenic activities at sea but the interactions and subsequent impacts can often be difficult to monitor, particularly in pelagic regions. Ireland and Britain in the north-eastern Atlantic Ocean host internationally important numbers of many seabird species. However, there are challenges in assessing their distribution at sea, not least the time and costs involved in trying to do this at the community level. The large territorial waters of both countries also provide significant prospective marine fossil fuels and renewable energy. Therefore, there is the potential for detrimental impacts to seabird populations where hotspots of seabird density overlap with marine energy activity. In this thesis I demonstrate how existing data can be combined to assess the at-sea distribution, vulnerability, and gaps in conservation protection of seabird species at the national scale. In Chapter 2, I use a distance-weighted, foraging radius approach to predict at-sea distributions (hereafter called foraging radius distributions) for all breeding seabirds in Britain and Ireland, identifying hotspots of highest density and species richness. Relatively simple foraging radius models have the potential to generate predictive distributions for a large number of species rapidly, thus providing a cost-effective alternative to large-scale surveys or complex modelling approaches. I calculate the percentage population coverage from current marine and coastal protected areas (MPAs) for all seabird species using foraging radius distributions. On average, 33% of coastal populations and 13% of pelagic populations overlap with MPAs, indicating that pelagic species, many of which are near threatened or endangered, have significantly less coverage from protected areas than coastal species. In Chapter 3, I test the effectiveness of the foraging-radius approach by comparing foraging radius distributions to empirical distribution data for multiple species taken from biotelemetry studies and aerial surveys. Foraging radius distributions correlate significantly with GPS tracking data for four species at the colony level. At the regional level, foraging radius distributions show mixed results when compared to aerial survey data, but correlate well with auks and terns in particular. In order to assess seabird vulnerability to oil pollution in European waters I develop a new Oil Vulnerability Index (OVI) that updates information on population size and conservation status, as well as accounting for the potential attraction/avoidance of seabirds to offshore infrastructure (Chapter 4). The OVI scores are applied spatially and overlaid with current offshore petroleum activities to generate maps of seabird vulnerability to oil pollution in the Irish EEZ. Finally, I combine all of the information on seabird distributions, vulnerability to anthropogenic activities, and designated MPAs to carry out a spatial prioritisation analysis for conservation of seabirds in Irish waters (Chapter 5). The results reveal that those areas in the Irish EEZ that are most important for seabird populations and that should be prioritised for conservation, are also the areas that are experiencing the most pressure from anthropogenic activities.