Session Title

Session S-09E: Marine, Freshwater and Terrestrial Species: Threats and Conservation

Conference Track

Species and Food Webs

Conference Name

Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Start Date

2-5-2014 10:30 AM

End Date

2-5-2014 12:00 PM

Abstract

The bluntnose sixgill shark, Hexanchus griseus, is a widely distributed but poorly understood large, apex predator. Anecdotal reports of diver-shark encounters in the late 1990’s and early 2000’s in the Pacific Northwest stimulated interest in the normally deep-dwelling shark and the reason for its presence in the shallow waters of the Salish Sea. Analysis of underwater video documenting sharks at the Seattle Aquarium’s sixgill research site on Seattle’s waterfront and mark-recapture techniques were used to identify individual sharks to answer simple questions about abundance and seasonality. Temporal changes in relative abundance in Puget Sound were reported from a controlled study site from 2003-2012. At the Seattle Aquarium study site, 45 sixgills were observed and tagged with modified Floy visual marker tags, along with an estimated 116 observations of untagged sharks. Mark/Recapture statistical model estimates based on video observations ranged from a high of 98 sharks observed in July of 2004 to a low of 0 sharks observed in several research events from 2008-2012. Both analyses found sixgills significantly more abundant in the summer months at the Aquarium’s research station from 2003-2005 than at any other time during the study.

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.

Language

English

Format

application/pdf

Type

Text

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May 2nd, 10:30 AM May 2nd, 12:00 PM

Observations on abundance of bluntnose sixgill sharks, Hexanchus griseus, in an urban waterway in the Salish Sea, 2003-2012

Room 613-614

The bluntnose sixgill shark, Hexanchus griseus, is a widely distributed but poorly understood large, apex predator. Anecdotal reports of diver-shark encounters in the late 1990’s and early 2000’s in the Pacific Northwest stimulated interest in the normally deep-dwelling shark and the reason for its presence in the shallow waters of the Salish Sea. Analysis of underwater video documenting sharks at the Seattle Aquarium’s sixgill research site on Seattle’s waterfront and mark-recapture techniques were used to identify individual sharks to answer simple questions about abundance and seasonality. Temporal changes in relative abundance in Puget Sound were reported from a controlled study site from 2003-2012. At the Seattle Aquarium study site, 45 sixgills were observed and tagged with modified Floy visual marker tags, along with an estimated 116 observations of untagged sharks. Mark/Recapture statistical model estimates based on video observations ranged from a high of 98 sharks observed in July of 2004 to a low of 0 sharks observed in several research events from 2008-2012. Both analyses found sixgills significantly more abundant in the summer months at the Aquarium’s research station from 2003-2005 than at any other time during the study.