Harbour seal haul-out monitoring, Sound of Islay. Scottish Natural Heritage Commissioned Report No. 894.

William Paterson, Deborah Jill Russell, Gi-Mick Wu, Bernie J McConnell, David Thompson

Research output: Book/ReportCommissioned report


The purpose of this report is to provide an overview of the current techniques available for monitoring seal haul-out sites either at the Sound of Islay or at haul-out sites elsewhere. This report builds on existing knowledge of harbour seal behaviour in the Sound of Islay and the South-East Islay Skerries SAC based on telemetry data collected in 2011 and 2012 with an assessment of data collected by GPS phone tags deployed in April 2014.
Main findings
 Controlled disturbance trials were carried out to assess the effect of disturbance by increased boat activity on haul-out behaviour. Concurrent monitoring of haul-out sites using remote camera systems recorded behavioural responses to trials, as well as giving daily seal counts at particular sites.
Modelling of transition probability indicated that controlled disturbance trials did not affect the probability of harbour seals transiting from one haul-out site to another. Seals generally displayed a high degree of site fidelity. The relationship between site fidelity and transition probability varied with whether seals hauled out again on the same or on a subsequent low tide period after a disturbance. Overall, seals were more likely to transit from one haul-out site to another if the trip in between included at least one high tide period.
The results of this study suggest that increased boat activity during the construction phase of the proposed tidal turbine development will not cause individual seals to transit from one haul-out site to another. If seals are flushed from their haulout they are likely to return to the same haul-out site either during the same or on a subsequent low tide period. The recommendation of this report is therefore that monitoring effort to mitigate against any perceived risk of an increase in levels of disturbance by boat need only be on a local scale relative to any proposed development.
In light of these results a simple, time lapse photography based method of haulout monitoring that should provide sufficient information to identify and characterise any boat based disturbance events is described
Original languageEnglish
PublisherScottish Natural Heritage
Commissioning bodyScottish Natural Heritage
Number of pages53
ISBN (Print)ISBN: 978-1-78391-354-1
Publication statusPublished - 2015


  • Harbour seal
  • marine renewables
  • haul-out
  • monitoring
  • disturbance
  • Sound of Islay


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