The Gulf menhaden stock is the target of a large commercial fishery in the Gulf of Mexico. To address the needs of both the stock and fishery, I performed two studies. I first addressed the natural mortality rates currently used in the Gulf menhaden stock assessment. To update these rates, I used data from a tagging study conducted from 1970 to 1988. Adult and juvenile menhaden were tagged, released, and recovered in fish processing plants. To evaluate the data, I built a Bayesian model using the negative binomial distribution to estimate natural mortality, catchability, and the overdispersion factor parameters. I established a Base model and n = 17 sensitivity models for robustness. I estimated a constant instantaneous natural mortality of 1.08 y-1 with 95% confidence intervals of 1.04 y-1 to 1.13 y-1. This estimate falls within the stock assessment confidence intervals, and validates the estimation of Ahrenholz (1981). These updated natural mortality rates can be directly used in the stock assessment. I then addressed the need for an implemented fishery reference point. For the fishery to provide verification of sustainability on an annual basis, the Gulf State Marine Fisheries Commission developed an index-based reference point through an algorithm adopted by managers and stakeholders. I developed a web-based application and 3 time series for the use and implementation of the fishery reference point. This dashboard uses processed fishery independent survey data and creates interactive elements for stakeholders to identify the risks of different threshold index values to be used for management.
","abstract_html":"<p>The Gulf menhaden stock is the target of a large commercial fishery in the Gulf of Mexico. To address the needs of both the stock and fishery, I performed two studies. I first addressed the natural mortality rates currently used in the Gulf menhaden stock assessment. To update these rates, I used data from a tagging study conducted from 1970 to 1988. Adult and juvenile menhaden were tagged, released, and recovered in fish processing plants. To evaluate the data, I built a Bayesian model using the negative binomial distribution to estimate natural mortality, catchability, and the overdispersion factor parameters. I established a Base model and n = 17 sensitivity models for robustness. I estimated a constant instantaneous natural mortality of 1.08 y<sup>-1</sup> with 95% confidence intervals of 1.04 y<sup>-1</sup> to 1.13 y<sup>-1</sup>. This estimate falls within the stock assessment confidence intervals, and validates the estimation of Ahrenholz (1981). These updated natural mortality rates can be directly used in the stock assessment. I then addressed the need for an implemented fishery reference point. For the fishery to provide verification of sustainability on an annual basis, the Gulf State Marine Fisheries Commission developed an index-based reference point through an algorithm adopted by managers and stakeholders. I developed a web-based application and 3 time series for the use and implementation of the fishery reference point. This dashboard uses processed fishery independent survey data and creates interactive elements for stakeholders to identify the risks of different threshold index values to be used for management.</p>","abstract_has_math":false,"creators":["Wilhelm, Catherine"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Masters Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Robert Leaf","Kim De Mutsert","Amy Schueller"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2023,"date_issued":"2023-05-01T07:00:00Z","date_published":"2023-05-01T07:00:00Z","updated_at":"2026-07-24T05:45:47Z","subjects":["ADMB","Quantitiative fisheries","Natural mortality","Gulf menhaden","Fishery reference point","Fisheries dashboard","Marine Biology"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aquila.usm.edu/masters_theses/997","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Robert Leaf","Kim De Mutsert","Amy Schueller"]},{"key":"dc:creator","label":"Author","values":["Wilhelm, Catherine"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2023-05-19T07:00:00Z"]},{"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":["ADMB","Quantitiative fisheries","Natural mortality","Gulf menhaden","Fishery reference point","Fisheries dashboard","Marine Biology"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://aquila.usm.edu/masters_theses/997"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The Gulf menhaden stock is the target of a large commercial fishery in the Gulf of Mexico. To address the needs of both the stock and fishery, I performed two studies. I first addressed the natural mortality rates currently used in the Gulf menhaden stock assessment. To update these rates, I used data from a tagging study conducted from 1970 to 1988. Adult and juvenile menhaden were tagged, released, and recovered in fish processing plants. To evaluate the data, I built a Bayesian model using the negative binomial distribution to estimate natural mortality, catchability, and the overdispersion factor parameters. I established a Base model and n = 17 sensitivity models for robustness. I estimated a constant instantaneous natural mortality of 1.08 y-1 with 95% confidence intervals of 1.04 y-1 to 1.13 y-1. This estimate falls within the stock assessment confidence intervals, and validates the estimation of Ahrenholz (1981). These updated natural mortality rates can be directly used in the stock assessment. I then addressed the need for an implemented fishery reference point. For the fishery to provide verification of sustainability on an annual basis, the Gulf State Marine Fisheries Commission developed an index-based reference point through an algorithm adopted by managers and stakeholders. I developed a web-based application and 3 time series for the use and implementation of the fishery reference point. This dashboard uses processed fishery independent survey data and creates interactive elements for stakeholders to identify the risks of different threshold index values to be used for management.
"]},{"key":"dc:title","label":"Title","values":["ESTIMATION OF MORTALITY RATES FOR THE GULF MENHADEN STOCK AND REFERENCE POINT IMPLEMENTATION FOR THE FISHERY"]}]}],"canonical_facts":{"dc:contributor":["Robert Leaf","Kim De Mutsert","Amy Schueller"],"dc:creator":["Wilhelm, Catherine"],"dc:date.available":["2023-05-19T07:00:00Z"],"dc:description.abstract":["The Gulf menhaden stock is the target of a large commercial fishery in the Gulf of Mexico. To address the needs of both the stock and fishery, I performed two studies. I first addressed the natural mortality rates currently used in the Gulf menhaden stock assessment. To update these rates, I used data from a tagging study conducted from 1970 to 1988. Adult and juvenile menhaden were tagged, released, and recovered in fish processing plants. To evaluate the data, I built a Bayesian model using the negative binomial distribution to estimate natural mortality, catchability, and the overdispersion factor parameters. I established a Base model and n = 17 sensitivity models for robustness. I estimated a constant instantaneous natural mortality of 1.08 y-1 with 95% confidence intervals of 1.04 y-1 to 1.13 y-1. This estimate falls within the stock assessment confidence intervals, and validates the estimation of Ahrenholz (1981). These updated natural mortality rates can be directly used in the stock assessment. I then addressed the need for an implemented fishery reference point. For the fishery to provide verification of sustainability on an annual basis, the Gulf State Marine Fisheries Commission developed an index-based reference point through an algorithm adopted by managers and stakeholders. I developed a web-based application and 3 time series for the use and implementation of the fishery reference point. This dashboard uses processed fishery independent survey data and creates interactive elements for stakeholders to identify the risks of different threshold index values to be used for management.
"],"dc:identifier":["https://aquila.usm.edu/masters_theses/997"],"dc:subject":["ADMB","Quantitiative fisheries","Natural mortality","Gulf menhaden","Fishery reference point","Fisheries dashboard","Marine Biology"],"dc:title":["ESTIMATION OF MORTALITY RATES FOR THE GULF MENHADEN STOCK AND REFERENCE POINT IMPLEMENTATION FOR THE FISHERY"],"thesis:degree_level":["Masters Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:45:47Z"}