Life History and Distribution of Two Species of Cownose Ray, Rhinoptera bonasus and Rhinoptera brasiliensis, in Mississippi Coastal Waters

<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>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Masters Thesis

Year dc:date.available

2025

Author dc:creator

• Millender, Anna

Contributors dc:contributor

• Dr. Wei Wu
• Mrs. Jill Hendon
• Dr. Michael Andres

• reproduction
• age
• growth
• maturity
• co-occurrence
• generalized linear models
• Aquaculture and Fisheries
• Biology
• Marine Biology
• Other Animal Sciences

Repository record dc:identifier

https://aquila.usm.edu/masters_theses/1163

OAI identifier oai:identifier

oai:aquila.usm.edu:masters_theses-2253