Exploring Fisheries Species Distribution Shifts in Response to Freshwater Inflow Through the Bonnet Carré Spillway Using Species Distribution Models

<p>The Bonnet Carre Spillway (BCS) is a flood control structure on the Mississippi River (MR) ~52 km upstream of New Orleans. The BCS protects downstream communities from MR flooding by diverting floodwaters into Lake Pontchartrain when the MR exceeds 5.18m flood stage. Diverted waters flow east into the Mississippi Sound (MSS), introducing turbid, nutrient rich freshwater to the estuary before draining into the Gulf of Mexico. BCS openings have become much more frequent in the last decade, though little work has been done to explore the impact of the BCS on nektonic fisheries species. Here, a series of seasonal Maximum Entropy (MaxEnt) species distribution models are constructed, validated, and performance-assessed to explore how BCS openings might affect <em>Brevoortia patronus</em>, <em>Cynoscion nebulosus</em>, and <em>Farfantepenaeus aztecus</em> in the space of the MSS and surrounding waters. Models are validated via 10-fold cross validation and assessed via area under curve analysis and a binomial test of training omission. The highest performing models are used to project species distribution over hydrodynamic simulations consistent with alternative operational regimes of the 2019 and 2020 BCS openings. Results indicate that the 2019 openings influenced nektonic species distribution, while the 2020 BCS opening had little impact on distribution. We found that reducing MR discharge at Baton Rouge only to the extent needed to reach 1.25 million cubic feet per second during the 2019 BCS openings would have minimized the distributional impact of these openings on <em>B. patronus</em>, <em>C. nebulosus</em>, and <em>F. aztecus</em> compared to all other candidate scenarios.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Masters Thesis

Year dc:date.available

2025

Author dc:creator

• May, David T

Contributors dc:contributor

• Dr. Kim de Mutsert
• Dr. Robert Leaf
• Dr. Wei Wu

• Species distribution models
• MaxEnt
• Bonnet Carre Spillway
• Estuaries
• Fisheries
• Modeling
• Terrestrial and Aquatic Ecology

Repository record dc:identifier

https://aquila.usm.edu/masters_theses/1142

OAI identifier oai:identifier

oai:aquila.usm.edu:masters_theses-2227