Title page for ETD etd-08202007-171122

Type of Document Master's Thesis
Author Graham, Larissa Joy
Author's Email Address ljgraham@vt.edu
URN etd-08202007-171122
Title Bycatch associated with a horseshoe crab (Limulus polyphemus) trawl survey: identifying species composition and distribution
Degree Master of Science
Department Fisheries and Wildlife Sciences
Advisory Committee
Advisor Name Title
Murphy, Brian R. Committee Chair
Berkson, James M. Committee Member
Hata, David Committee Member
  • trawl survey
  • fisheries management
  • width-weight relationship
  • horseshoe crab
  • bycatch
  • Middle Atlantic Bight
  • species composition
  • Multidimensional Scaling
Date of Defense 2007-08-02
Availability unrestricted
Horseshoe crabs (Limulus polyphemus) have been harvested along the east coast of the United States since the 1800s, however a Fishery Management Plan (FMP) was only recently created for this species. To date, there have not been any studies that have attempted to identify or quantify bycatch in the horseshoe crab trawl fishery. A horseshoe crab trawl survey was started in 2001 to collect data on the relative abundance, distribution, and population demographics of horseshoe crabs along the Atlantic coast of the United States. In the present study, species composition data were collected at sites sampled by the horseshoe crab trawl survey in 2005 and 2006. Seventy-six different taxa were identified as potential bycatch in the horseshoe crab trawl fishery. Non-metric multidimensional scaling (NMS) was used to cluster sites and identify the spatial distribution of taxa. Sites strongly clustered into distinct groups, suggesting that species composition changes spatially and seasonally. Species composition shifted between northern and southern sites. Location and bottom water temperature explain most of the variation in species composition. These results provide a list of species that are susceptible to this specific trawl gear and describe their distribution during fall months throughout the study area. Identifying these species and describing their distribution is a first step to understanding the ecosystem-level effects of the horseshoe crab trawl fishery.
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