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Department of Fisheries Oceanography PhD Dissertation Defense-Janne Haugen
- Location: > See description for location
- Contact: > See Description for contact information
- Description: The School for Marine Science and Technology
Department of Fisheries Oceanography
PhD Dissertation Defense
By Janne B. Haugen
"Fishery Management, Conservation, and Bycatch of North Atlantic Porbeagle (Lamna nasus)"
Friday, July 10, 2020
9:00 am
via Zoom
https://umassd.zoom.us/j/92591207832?pwd=THFPZ1lwQmtKNmZkaUxXd05CSlpsUT09
Meeting ID: 925 9120 7832 Password: 051191 +1 646 876 9923
Advisor:
Dr. Steven X. Cadrin, Professor and Chairperson, DFO, SMAST, UMD
Committee Members:
Dr. Pingguo He, Professor, DFO, SMAST, UMD
Dr. Geoffrey Cowles, Associate Professor, DFO, SMAST, UMD
Dr. Tobey Curtis, National Marine Fisheries Service, Highly Migratory Species Division
Dr. Gregory Skomal, Recreational Fisheries Program Manager, Massachusetts Division of Marine Fisheries
Abstract - Substantial effort has been devoted to improving fisheries management for conservation of elasmobranchs (sharks, skates, and rays) over the last two decades in response to worldwide population declines. Porbeagle (Lamna nasus), is one of the elasmobranchs with the longest history of exploitation in the North Atlantic and its conservation has been a concern for many years. Porbeagles are considered a data-limited species for stock assessments, and the goal of this dissertation was to fill research gaps for improving fishery management, conservation, and stock assessments for North Atlantic porbeagle. Chapter 1 reviewed management and conservation efforts related to North Atlantic porbeagle, and identified available data sources (i.e., trade statistics, economic value, recreational fisheries, observer programs and electronic monitoring) that are not currently being used in conservation or stock assessments of this data-limited species. By taking advantage of available data, efforts for new data collection may be more cost-effective for this data-limited species. Chapter 2 is an interdisciplinary review of all available information (i.e., life history, genetics, and movement) of North Atlantic porbeagle to evaluate population structure. Our review reveals different interpretations regarding the number of biological populations and stock boundaries among the organizations involved with the conservation and management of porbeagle in the North Atlantic. These inconsistencies can pose impediments to conserving porbeagle populations and achieving management objectives. Clearly defining management units that reflect the biological populations of porbeagle in the North Atlantic is expected to help achieve current and future management and conservation goals. Chapter 3 used the Northeast Fisheries Observer Program data to characterize porbeagle bycatch in seven fleets that have not previously been included in stock assessments and management of porbeagle (bottom otter trawl, haddock separator trawl, bottom otter trawl ruhle, midwater otter trawl, paired midwater trawl, fixed gillnet, and drift gillnet). Porbeagles had low at-vessel mortality in trawl gears (3 to 32 %) and relatively high mortality in gillnets (81 to 93 %). The Standardized Bycatch Reporting Methodology was adapted to estimate annual dead discards from the fleets that caught most porbeagles (bottom otter trawl, haddock separator trawl, fixed gillnet, and drift gillnet). Dead discards were variable and fluctuated between 47 and 758 mt for 2010-2018, primarily from fixed gillnets and bottom trawls. These catches are not included in porbeagle stock assessments or catch limits, but these estimates of recent discards are substantially greater than U.S. catch limits. Chapter 4 used Pop-up satellite archival transmitter tags to estimate the vertical susceptibility juvenile porbeagle to bycatch in the Gulf of Maine region (i.e., the time porbeagle spend at depths Gulf of Maine fishing gear operates in). The porbeagles spent 42% of their time near the surface (0 to 25 m deep, where pelagic longlines and midwater gillnets generally fish), 51 % in midwater (26 m deep to 12 m off the bottom, where some midwater trawls and purse seines fish), and 7 % at the bottom (bottom to 12 m off the bottom, where bottom trawls and most gillnets fish). The findings of this dissertation suggest that North Atlantic porbeagle is not as data-limited as previously thought. Some available data is not being considered in stock assessment and fishery management, and monitoring frameworks are in place to improve the conservation status and fisheries management of porbeagle. New information on discards, vertical susceptibility to bycatch, and other identified sources of data (e.g., recreational fishing, economic value, and trade statistics) can improve fisheries management and conservation of porbeagle if included in future stock assessments and conservation assessments.
- Topical Areas: School for Marine Sciences and Technology, SMAST Seminar Series
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