Blue crabs support a valuable commercial fishery in the Gulf of Mexico. Most states require the release of undersized and ovigerous blue crabs, yet mortality of these discarded crabs is an understudied component of total mortality. The first objective of this project was to quantify discard mortality of non-target crabs using bycatch surveys across the Lake Pontchartrain–Mississippi Sound coastal system. Ovigerous crabs were most common at high salinities and temperatures, whereas undersized crab presence was inversely correlated with soak time, temperature, and the number of crabs per trap, and also varied among geographic locations. A reflex action mortality prediction assessment (RAMP) was used to assess mortality likelihood. For non-ovigerous crabs, RAMP score was positively correlated with soak time. For ovigerous crabs, RAMP score was positively associated with carapace width and soak time and varied among geographic locations. Estimated discard mortality rates, expressed as a percentage of total catch, ranged from 0.07%–0.48% in Lake Pontchartrain, 0.04%–0.95% in Western Mississippi Sound, and 0%–3.67% in Central Mississippi Sound. The second objective experimentally tested the impact of handling practices on mortality of discarded crabs. Non-target crabs captured in traps were subjected to one of eight handling treatments mimicking commercial practices. Ovigerous crabs had lower survival than undersized crabs. Undersized crabs exhibited nearly 100% survival when released immediately, although survival decreased with delayed release. Results will aid understanding of discard mortality and inform best practices.
","abstract_html":"<p>Blue crabs support a valuable commercial fishery in the Gulf of Mexico. Most states require the release of undersized and ovigerous blue crabs, yet mortality of these discarded crabs is an understudied component of total mortality. The first objective of this project was to quantify discard mortality of non-target crabs using bycatch surveys across the Lake Pontchartrain–Mississippi Sound coastal system. Ovigerous crabs were most common at high salinities and temperatures, whereas undersized crab presence was inversely correlated with soak time, temperature, and the number of crabs per trap, and also varied among geographic locations. A reflex action mortality prediction assessment (RAMP) was used to assess mortality likelihood. For non-ovigerous crabs, RAMP score was positively correlated with soak time. For ovigerous crabs, RAMP score was positively associated with carapace width and soak time and varied among geographic locations. Estimated discard mortality rates, expressed as a percentage of total catch, ranged from 0.07%–0.48% in Lake Pontchartrain, 0.04%–0.95% in Western Mississippi Sound, and 0%–3.67% in Central Mississippi Sound. The second objective experimentally tested the impact of handling practices on mortality of discarded crabs. Non-target crabs captured in traps were subjected to one of eight handling treatments mimicking commercial practices. Ovigerous crabs had lower survival than undersized crabs. Undersized crabs exhibited nearly 100% survival when released immediately, although survival decreased with delayed release. Results will aid understanding of discard mortality and inform best practices.</p>","abstract_has_math":false,"creators":["Cochran, Micayla"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Masters Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Dr. Zachary Darnell","Dr. Kim De Mutsert","Dr. Marcus Drymon"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2026,"date_issued":"2026-05-01T07:00:00Z","date_published":"2026-05-01T07:00:00Z","updated_at":"2026-07-24T05:45:55Z","subjects":["bycatch","commercial fishery","fishery management","Louisiana","Mississippi","population dynamics","Natural Resources Management and Policy"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aquila.usm.edu/masters_theses/1189","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Dr. Zachary Darnell","Dr. Kim De Mutsert","Dr. Marcus Drymon"]},{"key":"dc:creator","label":"Author","values":["Cochran, Micayla"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2026-06-01T07:00:00Z"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Masters Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["bycatch","commercial fishery","fishery management","Louisiana","Mississippi","population dynamics","Natural Resources Management and Policy"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://aquila.usm.edu/masters_theses/1189"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Blue crabs support a valuable commercial fishery in the Gulf of Mexico. Most states require the release of undersized and ovigerous blue crabs, yet mortality of these discarded crabs is an understudied component of total mortality. The first objective of this project was to quantify discard mortality of non-target crabs using bycatch surveys across the Lake Pontchartrain–Mississippi Sound coastal system. Ovigerous crabs were most common at high salinities and temperatures, whereas undersized crab presence was inversely correlated with soak time, temperature, and the number of crabs per trap, and also varied among geographic locations. A reflex action mortality prediction assessment (RAMP) was used to assess mortality likelihood. For non-ovigerous crabs, RAMP score was positively correlated with soak time. For ovigerous crabs, RAMP score was positively associated with carapace width and soak time and varied among geographic locations. Estimated discard mortality rates, expressed as a percentage of total catch, ranged from 0.07%–0.48% in Lake Pontchartrain, 0.04%–0.95% in Western Mississippi Sound, and 0%–3.67% in Central Mississippi Sound. The second objective experimentally tested the impact of handling practices on mortality of discarded crabs. Non-target crabs captured in traps were subjected to one of eight handling treatments mimicking commercial practices. Ovigerous crabs had lower survival than undersized crabs. Undersized crabs exhibited nearly 100% survival when released immediately, although survival decreased with delayed release. Results will aid understanding of discard mortality and inform best practices.
"]},{"key":"dc:title","label":"Title","values":["Quantifying Discard Mortality of Undersized and Ovigerous Crabs in the Gulf of Mexico Blue Crab Fishery"]}]}],"canonical_facts":{"dc:contributor":["Dr. Zachary Darnell","Dr. Kim De Mutsert","Dr. Marcus Drymon"],"dc:creator":["Cochran, Micayla"],"dc:date.available":["2026-06-01T07:00:00Z"],"dc:description.abstract":["Blue crabs support a valuable commercial fishery in the Gulf of Mexico. Most states require the release of undersized and ovigerous blue crabs, yet mortality of these discarded crabs is an understudied component of total mortality. The first objective of this project was to quantify discard mortality of non-target crabs using bycatch surveys across the Lake Pontchartrain–Mississippi Sound coastal system. Ovigerous crabs were most common at high salinities and temperatures, whereas undersized crab presence was inversely correlated with soak time, temperature, and the number of crabs per trap, and also varied among geographic locations. A reflex action mortality prediction assessment (RAMP) was used to assess mortality likelihood. For non-ovigerous crabs, RAMP score was positively correlated with soak time. For ovigerous crabs, RAMP score was positively associated with carapace width and soak time and varied among geographic locations. Estimated discard mortality rates, expressed as a percentage of total catch, ranged from 0.07%–0.48% in Lake Pontchartrain, 0.04%–0.95% in Western Mississippi Sound, and 0%–3.67% in Central Mississippi Sound. The second objective experimentally tested the impact of handling practices on mortality of discarded crabs. Non-target crabs captured in traps were subjected to one of eight handling treatments mimicking commercial practices. Ovigerous crabs had lower survival than undersized crabs. Undersized crabs exhibited nearly 100% survival when released immediately, although survival decreased with delayed release. Results will aid understanding of discard mortality and inform best practices.
"],"dc:identifier":["https://aquila.usm.edu/masters_theses/1189"],"dc:subject":["bycatch","commercial fishery","fishery management","Louisiana","Mississippi","population dynamics","Natural Resources Management and Policy"],"dc:title":["Quantifying Discard Mortality of Undersized and Ovigerous Crabs in the Gulf of Mexico Blue Crab Fishery"],"thesis:degree_level":["Masters Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:45:55Z"}