Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004
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...
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ftwilliammarycol:oai:scholarworks.wm.edu:etd-2246 2023-06-11T04:15:03+02:00 Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004 Ha, Daniel Stuart 2006-01-01T08:00:00Z application/pdf https://scholarworks.wm.edu/etd/1539616679 https://doi.org/10.25773/v5-masw-m267 https://scholarworks.wm.edu/context/etd/article/2246/viewcontent/3209549.pdf English eng W&M ScholarWorks https://scholarworks.wm.edu/etd/1539616679 doi:doi:10.25773/v5-masw-m267 https://scholarworks.wm.edu/context/etd/article/2246/viewcontent/3209549.pdf © The Author Dissertations, Theses, and Masters Projects Aquaculture and Fisheries Marine Biology Zoology text 2006 ftwilliammarycol https://doi.org/10.25773/v5-masw-m267 2023-05-04T17:56:55Z 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 the survey. Only two species showed no significant trends, and only one (C. obscurus) showed signs of recovery. Analysis of size changes showed that both C. plumbeus and C. obscurus have suffered declines in both mean and variance of their size distribution since 1974. Analyses of mass changes showed that five of thirteen species have shown biologically significant declines in mass per shark since 1974. Six of the remaining eight showed no trend in mass per shark. Habitat analyses showed that few species showed effects of climate scale variables such as the North Atlantic Oscillation index, Chesapeake Bay discharge, or the Palmer Drought Index. Many species showed significant changes in patterns in abundance with local environmental variables, such as temperature, salinity, and water depth. These patterns, when combined, revealed several groupings of species, including deep-water species, Bay-abundant species, and near-shore species. Another group consisted of species that occur in this area only as they move north and south en route to more northerly areas for summer months. One group was made up of two species (S. acanthias and M. canis) that occurred almost exclusively in cold water (April and May). Analysis of New Jersey long-line data from 1961-62 with a resample of many of the same sites revealed that abundances off New Jersey show a trend in both mass and abundance similar to ... Text North Atlantic North Atlantic oscillation W&M ScholarWorks Gam ENVELOPE(-57.955,-57.955,-61.923,-61.923) |
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Aquaculture and Fisheries Marine Biology Zoology |
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Aquaculture and Fisheries Marine Biology Zoology Ha, Daniel Stuart Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004 |
topic_facet |
Aquaculture and Fisheries Marine Biology Zoology |
description |
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 the survey. Only two species showed no significant trends, and only one (C. obscurus) showed signs of recovery. Analysis of size changes showed that both C. plumbeus and C. obscurus have suffered declines in both mean and variance of their size distribution since 1974. Analyses of mass changes showed that five of thirteen species have shown biologically significant declines in mass per shark since 1974. Six of the remaining eight showed no trend in mass per shark. Habitat analyses showed that few species showed effects of climate scale variables such as the North Atlantic Oscillation index, Chesapeake Bay discharge, or the Palmer Drought Index. Many species showed significant changes in patterns in abundance with local environmental variables, such as temperature, salinity, and water depth. These patterns, when combined, revealed several groupings of species, including deep-water species, Bay-abundant species, and near-shore species. Another group consisted of species that occur in this area only as they move north and south en route to more northerly areas for summer months. One group was made up of two species (S. acanthias and M. canis) that occurred almost exclusively in cold water (April and May). Analysis of New Jersey long-line data from 1961-62 with a resample of many of the same sites revealed that abundances off New Jersey show a trend in both mass and abundance similar to ... |
format |
Text |
author |
Ha, Daniel Stuart |
author_facet |
Ha, Daniel Stuart |
author_sort |
Ha, Daniel Stuart |
title |
Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004 |
title_short |
Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004 |
title_full |
Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004 |
title_fullStr |
Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004 |
title_full_unstemmed |
Ecology and conservation of Virginia shark species: Analysis of thirty years of Virginia long-line shark census data, 1974--2004 |
title_sort |
ecology and conservation of virginia shark species: analysis of thirty years of virginia long-line shark census data, 1974--2004 |
publisher |
W&M ScholarWorks |
publishDate |
2006 |
url |
https://scholarworks.wm.edu/etd/1539616679 https://doi.org/10.25773/v5-masw-m267 https://scholarworks.wm.edu/context/etd/article/2246/viewcontent/3209549.pdf |
long_lat |
ENVELOPE(-57.955,-57.955,-61.923,-61.923) |
geographic |
Gam |
geographic_facet |
Gam |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_source |
Dissertations, Theses, and Masters Projects |
op_relation |
https://scholarworks.wm.edu/etd/1539616679 doi:doi:10.25773/v5-masw-m267 https://scholarworks.wm.edu/context/etd/article/2246/viewcontent/3209549.pdf |
op_rights |
© The Author |
op_doi |
https://doi.org/10.25773/v5-masw-m267 |
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1768371552397557760 |