5-8 Telemetry-based mortality estimates of juvenile spot in two North Carolina estuarine creeks

Monday, September 13, 2010: 3:40 PM
317 (Convention Center)
Sarah E. Friedl , Biology, North Carolina State University Center for Marine Sciences and Technology, Morehead City, NC
Jeffrey A. Buckel, PhD , Biology, North Carolina State University Center for Marine Sciences and Technology, Morehead City, NC
Joseph E. Hightower, PhD , Biology, U.S. Geological Survey, North Carolina State University, Raleigh, NC
Frederick S. Scharf, PhD , Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC
Kenneth H. Pollock, PhD , School of Biological Sciences and Biotechnology, Murdoch University, Murdoch, Western Australia, Australia

We directly estimated natural mortality rates (M) of juvenile spot (Leiostomus xanthurus) using a sonic telemetry approach. In spring of 2009, we surgically implanted 48 age-1 spot (mean weight 69.0g; mean FL 161.9mm) with sonic transmitters in two North Carolina creeks. Spot were tracked for 80 days using a stationary VR2 receiver array and manual tracking.  No spot stopped moving during the study period and swimming speeds (≤0.5m/s) did not indicate predation events.  Many of the telemetered spot exhibited a similar diel change in location and swimming speed at dawn and dusk with more activity during diurnal compared to nocturnal periods.   Potential spot predators were collected using gill and trammel nets and stomach content analysis confirmed that predation events were unlikely.  Our estimated M of 0 was based on a mean period at risk of 22 d. Lorenzen’s (1996) model predicts that M over a 22 d period would be 0.053 for this size fish.  Low observed natural mortality in estuarine creeks has implications for the stock assessment and management of this species.

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