Increasing numbers of harbour seals and grey seals in the Solent ...

• Main Authors: Marley, Sarah, Castles, Robyne, Woods, Fiona, Hughes, Peter, Arnott, John, MacCallum, Louise
• Format: Dataset
• Language: English
• Published: Dryad 2021
• Subjects: FOS: Biological sciences; Marine biology; harbour seals; grey seal; photo-identification; Phoca vitulina
• Online Access: https://dx.doi.org/10.5061/dryad.5tb2rbp4v; https://datadryad.org/stash/dataset/doi:10.5061/dryad.5tb2rbp4v

Harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) both occur within the UK, but display regional contrasting population trends. Whilst grey seals are typically increasing in number, harbour seals have shown varying trends in recent decades following repeated pandemics. There is a need for monitoring of regional and local populations to understand overall trends. This study utilised a 20-year dataset of seal counts from two neighbouring harbours in the Solent region of south England. Generalised additive models showed a significant increase in the numbers of harbour (mean 5.3 to 30.5) and grey seals (mean 0 to 12.0) utilising Chichester Harbour. Conversely, in Langstone Harbour there has been a slight decrease in the number of harbour seals (mean 5.3 to 4.0). Accompanying photographic data from 2016-18 supports the increase in seal numbers within Chichester Harbour, with a total of 68 harbour and 8 grey seals identified. These data also show evidence of site fidelity of harbour seals in this ... : Study Area The Solent is a sheltered channel system, separated from the English Channel by the Isle of Wight and stretching along the coastline of Hampshire and West Sussex (Figure 1). It includes numerous estuaries and natural harbours, the largest of which are Portsmouth, Langstone, and Chichester Harbours, which form a series of connected basins comprised of extensive intertidal mud and sand banks. Previous studies have confirmed that harbour seals utilise haul-outs in both Chichester and Langstone Harbours, moving between these sites via both the sea and a network of tidal channels (Chesworth et al., 2010). Grey seals have previously only been reported in a single sighting located within Chichester Harbour (Chesworth et al., 2010). Data Collection Visual surveys were undertaken in Chichester Harbour from 1999 to 2012 and 2015 to 2019, with surveys in Langstone Harbour from 2009 to 2017 and 2019 (Appendix 1). Surveys approximately overlapped with low tide, when the tidal mud flats were at their maximum ...