Prevalence of propeller strike related mortality in harbor seals (Phoca vitulina) from San Juan County, WA
Presentation Abstract
Documenting human interaction (e.g., boat collisions, gunshot wounds and fishery interactions) in marine mammal strandings is necessary to understand anthropogenic impacts and can be used to inform stock assessments as well as policy and management decisions. Boat propellers can inflict serious harm to marine mammals and the associated injuries are often fatal, however little is known about their impact on harbor seals in the region. A retrospective analysis of harbor seal (Phoca vitulina) strandings in San Juan County, WA revealed a 1.1% prevalence (8/718) of propeller strike mortality since the first clearly documented case in 2006. All eight cases were investigated by individuals trained to respond to marine mammal strandings and six freshly dead carcasses received complete necropsies. Diagnoses were based on established evidence of propeller strike injuries including cleanly incised wounds, uniform spacing between lacerations, and one eye-witness account. Propeller strike injuries were found in both males (50%) and females (37.5%) and one animal of unknown sex (14.2%). All eight cases involved nursing or weaned pups, which is consistent with previous findings suggesting immature age classes are particularly vulnerable to this type of injury. Propeller strikes have been associated with an Unusual Mortality Event (UME) of pinnipeds in the United Kingdom and may have the potential to impact species at the population level. Baseline data on prevalence of propeller strikes in a harbor seal population at carrying capacity serves as a reference for struggling pinniped stocks where little data on propeller induced mortality is available, but could potentially impact population recovery.
Session Title
Local Stories and Results
Conference Track
Salish Sea Snapshots
Conference Name
Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)
Document Type
Event
Start Date
2016 12:00 AM
End Date
2016 12:00 AM
Location
2016SSEC
Type of Presentation
Snapshot
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Harbor seal--Mortality--Washington (State)--San Juan County; Harbor seal--Effect of human beings on--Washington (State)--San Juan County; Harbor seal--Wounds and injuries--Washington (State)--San Juan County
Geographic Coverage
San Juan County (Wash.); Salish Sea (B.C. and Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Prevalence of propeller strike related mortality in harbor seals (Phoca vitulina) from San Juan County, WA
2016SSEC
Documenting human interaction (e.g., boat collisions, gunshot wounds and fishery interactions) in marine mammal strandings is necessary to understand anthropogenic impacts and can be used to inform stock assessments as well as policy and management decisions. Boat propellers can inflict serious harm to marine mammals and the associated injuries are often fatal, however little is known about their impact on harbor seals in the region. A retrospective analysis of harbor seal (Phoca vitulina) strandings in San Juan County, WA revealed a 1.1% prevalence (8/718) of propeller strike mortality since the first clearly documented case in 2006. All eight cases were investigated by individuals trained to respond to marine mammal strandings and six freshly dead carcasses received complete necropsies. Diagnoses were based on established evidence of propeller strike injuries including cleanly incised wounds, uniform spacing between lacerations, and one eye-witness account. Propeller strike injuries were found in both males (50%) and females (37.5%) and one animal of unknown sex (14.2%). All eight cases involved nursing or weaned pups, which is consistent with previous findings suggesting immature age classes are particularly vulnerable to this type of injury. Propeller strikes have been associated with an Unusual Mortality Event (UME) of pinnipeds in the United Kingdom and may have the potential to impact species at the population level. Baseline data on prevalence of propeller strikes in a harbor seal population at carrying capacity serves as a reference for struggling pinniped stocks where little data on propeller induced mortality is available, but could potentially impact population recovery.
