Abstract Title

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

Keywords

Species and Food Webs

Location

Room 613-614

Start Date

2-5-2014 10:30 AM

End Date

2-5-2014 12:00 PM

Description

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.

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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.