Review of analytical approaches for identifying usage and foraging areas at sea for harbour seals

• Main Authors: Jones, Esther Lane, Smout, Sophie Caroline, Russell, Deborah Jill, Pinn, Eunice, McConnell, Bernie J
• Format: Book
• Language: English
• Published: Joint Nature Conservation Committee 2017
• Subjects: harbour seal; Phoca vitulina
• Online Access: https://risweb.st-andrews.ac.uk/portal/en/researchoutput/review-of-analytical-approaches-for-identifying-usage-and-foraging-areas-at-sea-for-harbour-seals(8ac93c94-6246-4ac4-a325-5ad4f0b952bd).html; http://jncc.defra.gov.uk/pdf/Report_602_WEB.pdf

The purpose of this report is to build upon the outputs of work undertaken by the Sea Mammal Research Unit (SMRU, University of St Andrews) funded by the Department of Energy and Climatic Change (DECC) and the Scottish Government, in order to draw these strands of work together with the aim of identifying whether discrete and persistent foraging areas for harbour seals (Phoca vitulina) can be identified in the UK marine area. A usage map of harbour seal at-sea distribution is presented in order to identify important at-sea areas for the species. Usage is the estimate of the instantaneous density of seals at sea. This is based upon movement data derived from 277 telemetry tags deployed between 2003 and 2013, combined with terrestrial haul-out count data from 1996 to 2013. These data were collected by two tag types: Satellite Relay Data Loggers (SRDL) that use the Argos satellite system for location estimation and data transmission, and GPS phone tags that use the GSM mobile phone network for data transmission. The usage map extends to the limit of UK harbour seal movements and has a spatial resolution of 5km x 5km. Seal usage within the 5km x 5km cells is estimated (using current and historical data where appropriate) for the year 2013. The data do not support breaking down this usage map by year, season, or by the intrinsic properties of seal age or sex. Uncertainty is incorporated into the usage map estimation so that 95% confidence intervals of individual cell usage are available. Regional significance is demonstrated by dividing the usage map into five Harbour Seal Areas (HSAs). Within each HSA, grid cells are ranked in descending order based on the estimated usage in each cell. Grid cells are selected, beginning with the most intensively used cells, until 10% of the total usage of each HSA is included. This is repeated in 10% increments (up to 90%) of individual HSA usage and the resulting maps are presented. Usage maps could be made more accurate with strategically-located future deployments of tags. This ...