Historically, the American Cownose Ray (Rhinoptera bonasus) was considered the only rhinopterid residing in the northern Gulf of Mexico (GOM); however, recent studies have confirmed the presence of the Brazilian Cownose Ray (Rhinoptera brasiliensis) throughout this region. The current study investigated the life history and distribution of both species within Mississippi waters, an area that previously represented a data gap for both species. From April 2016 – July 2025, 193 R. bonasus and 94 R. brasiliensis were analyzed to describe the reproductive biology. Reproductive timing, mating, gestation length, and parturition were similar among species. Although more samples are needed to confirm, we provide evidence of a larger size-at-maturity and size-at-birth for R. brasiliensis. Age and growth estimates were determined from 106 R. bonasus and 68 R. brasiliensis. Ages ranged from 0+ to 10+ years for R. bonasus and 0+ to 12+ years for R. brasiliensis. Rhinoptera brasiliensis showed evidence of maturing at a later age, reaching a larger size, a higher theoretical age, and growing faster than R. bonasus. Lastly, drivers of distribution were investigated between March 2010 – July 2025. Salinity and depth were the main predictors of occurrence for both species; however, increased salinity was negatively associated with R. bonasus and positively associated with R. brasiliensis within a certain threshold. The current study provides updated life history estimates for R. bonasus and initial estimates for R. brasiliensis within the northern GOM. Additionally, this study provides the first investigation of drivers of co-occurrence of both species within Mississippi coastal waters.
","abstract_html":"<p>Historically, the American Cownose Ray (<em>Rhinoptera bonasus</em>) was considered the only rhinopterid residing in the northern Gulf of Mexico (GOM); however, recent studies have confirmed the presence of the Brazilian Cownose Ray (<em>Rhinoptera brasiliensis</em>) throughout this region. The current study investigated the life history and distribution of both species within Mississippi waters, an area that previously represented a data gap for both species. From April 2016 – July 2025, 193 <em>R. bonasus</em> and 94 <em>R. brasiliensis</em> were analyzed to describe the reproductive biology. Reproductive timing, mating, gestation length, and parturition were similar among species. Although more samples are needed to confirm, we provide evidence of a larger size-at-maturity and size-at-birth for <em>R. brasiliensis</em>. Age and growth estimates were determined from 106 <em>R. bonasus</em> and 68 <em>R. brasiliensis</em>. Ages ranged from 0+ to 10+ years for <em>R. bonasus</em> and 0+ to 12+ years for <em>R. brasiliensis</em>. <em>Rhinoptera brasiliensis</em> showed evidence of maturing at a later age, reaching a larger size, a higher theoretical age, and growing faster than <em>R. bonasus. </em>Lastly, drivers of distribution were investigated between March 2010 – July 2025. Salinity and depth were the main predictors of occurrence for both species; however, increased salinity was negatively associated with <em>R. bonasus</em> and positively associated with <em>R. brasiliensis</em> within a certain threshold. The current study provides updated life history estimates for <em>R. bonasus</em> and initial estimates for <em>R. brasiliensis</em> within the northern GOM. Additionally, this study provides the first investigation of drivers of co-occurrence of both species within Mississippi coastal waters.</p>","abstract_has_math":false,"creators":["Millender, Anna"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Masters Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Dr. Wei Wu","Mrs. Jill Hendon","Dr. Michael Andres"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-12-01T08:00:00Z","date_published":"2025-12-01T08:00:00Z","updated_at":"2026-07-24T05:45:55Z","subjects":["reproduction","age","growth","maturity","co-occurrence","generalized linear models","Aquaculture and Fisheries","Biology","Marine Biology","Other Animal Sciences"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aquila.usm.edu/masters_theses/1163","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Dr. Wei Wu","Mrs. Jill Hendon","Dr. Michael Andres"]},{"key":"dc:creator","label":"Author","values":["Millender, Anna"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2026-01-01T08:00:00Z"]},{"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":["reproduction","age","growth","maturity","co-occurrence","generalized linear models","Aquaculture and Fisheries","Biology","Marine Biology","Other Animal Sciences"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://aquila.usm.edu/masters_theses/1163"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Historically, the American Cownose Ray (Rhinoptera bonasus) was considered the only rhinopterid residing in the northern Gulf of Mexico (GOM); however, recent studies have confirmed the presence of the Brazilian Cownose Ray (Rhinoptera brasiliensis) throughout this region. The current study investigated the life history and distribution of both species within Mississippi waters, an area that previously represented a data gap for both species. From April 2016 – July 2025, 193 R. bonasus and 94 R. brasiliensis were analyzed to describe the reproductive biology. Reproductive timing, mating, gestation length, and parturition were similar among species. Although more samples are needed to confirm, we provide evidence of a larger size-at-maturity and size-at-birth for R. brasiliensis. Age and growth estimates were determined from 106 R. bonasus and 68 R. brasiliensis. Ages ranged from 0+ to 10+ years for R. bonasus and 0+ to 12+ years for R. brasiliensis. Rhinoptera brasiliensis showed evidence of maturing at a later age, reaching a larger size, a higher theoretical age, and growing faster than R. bonasus. Lastly, drivers of distribution were investigated between March 2010 – July 2025. Salinity and depth were the main predictors of occurrence for both species; however, increased salinity was negatively associated with R. bonasus and positively associated with R. brasiliensis within a certain threshold. The current study provides updated life history estimates for R. bonasus and initial estimates for R. brasiliensis within the northern GOM. Additionally, this study provides the first investigation of drivers of co-occurrence of both species within Mississippi coastal waters.
"]},{"key":"dc:title","label":"Title","values":["Life History and Distribution of Two Species of Cownose Ray, Rhinoptera bonasus and Rhinoptera brasiliensis, in Mississippi Coastal Waters"]}]}],"canonical_facts":{"dc:contributor":["Dr. Wei Wu","Mrs. Jill Hendon","Dr. Michael Andres"],"dc:creator":["Millender, Anna"],"dc:date.available":["2026-01-01T08:00:00Z"],"dc:description.abstract":["Historically, the American Cownose Ray (Rhinoptera bonasus) was considered the only rhinopterid residing in the northern Gulf of Mexico (GOM); however, recent studies have confirmed the presence of the Brazilian Cownose Ray (Rhinoptera brasiliensis) throughout this region. The current study investigated the life history and distribution of both species within Mississippi waters, an area that previously represented a data gap for both species. From April 2016 – July 2025, 193 R. bonasus and 94 R. brasiliensis were analyzed to describe the reproductive biology. Reproductive timing, mating, gestation length, and parturition were similar among species. Although more samples are needed to confirm, we provide evidence of a larger size-at-maturity and size-at-birth for R. brasiliensis. Age and growth estimates were determined from 106 R. bonasus and 68 R. brasiliensis. Ages ranged from 0+ to 10+ years for R. bonasus and 0+ to 12+ years for R. brasiliensis. Rhinoptera brasiliensis showed evidence of maturing at a later age, reaching a larger size, a higher theoretical age, and growing faster than R. bonasus. Lastly, drivers of distribution were investigated between March 2010 – July 2025. Salinity and depth were the main predictors of occurrence for both species; however, increased salinity was negatively associated with R. bonasus and positively associated with R. brasiliensis within a certain threshold. The current study provides updated life history estimates for R. bonasus and initial estimates for R. brasiliensis within the northern GOM. Additionally, this study provides the first investigation of drivers of co-occurrence of both species within Mississippi coastal waters.
"],"dc:identifier":["https://aquila.usm.edu/masters_theses/1163"],"dc:subject":["reproduction","age","growth","maturity","co-occurrence","generalized linear models","Aquaculture and Fisheries","Biology","Marine Biology","Other Animal Sciences"],"dc:title":["Life History and Distribution of Two Species of Cownose Ray, Rhinoptera bonasus and Rhinoptera brasiliensis, in Mississippi Coastal Waters"],"thesis:degree_level":["Masters Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:45:55Z"}