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Ecology And Conservation Of Virginia Shark Species: Analysis Of Thirty Years Of Virginia Long-Line Shark Census Data, 1974--2004, Daniel Stuart Ha
Ecology And Conservation Of Virginia Shark Species: Analysis Of Thirty Years Of Virginia Long-Line Shark Census Data, 1974--2004, Daniel Stuart Ha
Dissertations, Theses, and Masters Projects
Sharks of the Atlantic coast of the United States have suffered increased fishing pressure in last three decades. Commercial and recreational catches jumped in the mid to late 1980's, leading to regulation by the National Marine Fisheries Service in the early 1990's. The Virginia Institute of Marine Sciences' shark long-line survey, begun in 1974, and continuing to the present day, is thus well positioned to look at the effects of this fishing mortality on sharks. Using GAM modelling, six of ten shark species analyzed, including the most common species, Carcharhinus plumbeus, suffered declines of from 98-99% of early abundances in …
Development Of Generalized Index-Removal Models, With Particular Attention To Catchability Issues, Thomas F. Ihde
Development Of Generalized Index-Removal Models, With Particular Attention To Catchability Issues, Thomas F. Ihde
Dissertations, Theses, and Masters Projects
The index-removal method estimates abundance, exploitation and catchability coefficient, given surveys conducted before and after a known removal. The method assumes a closed population between surveys. Index-removal has seldom been applied due to its strong assumption of constant survey catchabilities. This work generalizes the method to allow multiple years of data to be incorporated, and the assumptions of the original model to be relaxed. If catchability is constant across years, precision can be improved by analyzing multi-year data simultaneously. Two multiple-year models were developed: the first, 1qIR, assumes constant catchability within and among years; the second, 2qIR, allows catchability to …
Habitat Utilization And Salinity Tolerance Of The Sandbar Shark, Carcharhinus Plumbeus, In Virginia, Leonard Pace
Habitat Utilization And Salinity Tolerance Of The Sandbar Shark, Carcharhinus Plumbeus, In Virginia, Leonard Pace
Dissertations, Theses, and Masters Projects
No abstract provided.
Migratory And Spawning Behavior Of American Shad In The James River, Virginia, Aaron W. Aunins
Migratory And Spawning Behavior Of American Shad In The James River, Virginia, Aaron W. Aunins
Dissertations, Theses, and Masters Projects
No abstract provided.
Sources Of Mortality, Movements And Behavior Of Sea Turtles In Virginia, Katherine Lamont. Mansfield
Sources Of Mortality, Movements And Behavior Of Sea Turtles In Virginia, Katherine Lamont. Mansfield
Dissertations, Theses, and Masters Projects
Aerial surveys are commonly used to evaluate in-water sea turtle abundances. A correction is applied to account for turtles diving below the observed surface. Historically, observations of summer/fall surfacing behavior were used for this correction, assuming constant behavior among seasons. Using radio/acoustic telemetry, seasonal differences in sea turtle surfacing behavior were determined among Kemp's ridleys and loggerheads. Mean time spent at surface in the spring ranged between 9.9%-30.0% with significant differences among individuals. Observed surfacing times were higher than historic summer/fall observations (Byles 1988; 5.3%), indicating that historic springtime abundances were overestimated by 50%-80%. Aerial surveys (2001-2004) indicated a 65%-75% …