Understanding and Managing Living Resources

This year marks fourteen years of collaboration within the Gulf of Mexico (GOM) to address the aftermath of the Deepwater Horizon oil spill. As part of this collective effort, the Mississippi Based RESTORE Act Center of Excellence (MBRACE), Mississippi Department of Environmental Quality, and Mississippi Department of Marine Resources have established a mutually beneficial relationship to enhance coordination and collaboration among researchers funded by Deepwater Horizon penalty funds and state agencies. We aim to support research that contributes to effective management of the Gulf of Mexico ecosystem. The collaborative process begins with identification of research topics through a joint effort in formulating Requests for Proposals. This ensures that research initiatives align with pressing needs of restoration practitioners and resource managers, fostering research that is not only scientifically rigorous but directly applicable to management decisions. A recent highlight of our collaboration is a MBRACE hosted Research to Application Workshop where researchers presented project plans and engaged in discussions with state agency representatives. This unique platform allowed for a two-way exchange where researchers gain valuable insights and feedback on their projects and state agencies provide crucial information on study locations and share existing data to enrich research endeavors. Through these co-produced projects, we aim to demonstrate the effectiveness of collaborative efforts for informing specific natural resource management decisions. As the Gulf's data landscape evolves, there is a growing realization of the need for dedicated synthesis initiatives. Our presentation will discuss the value of investing in such initiatives, emphasizing how a structured approach can meet the evolving goals of the Gulf community. We believe this case study exemplifies the importance of fostering ongoing dialogue and collaboration between organizations like MBRACE and state agencies for the successful application of research that is scientifically robust and directly informs management decisions in the GOM.

Common bottlenose dolphins (Tursiops truncatus) are difficult to study because they occupy marine habitats that are not easily accessible to humans, they are able to travel large distances, and researchers are limited to brief glimpses above the water and post-encounter identification to try to explain on-water behaviors. As a result, most dolphin studies focus on isolated populations in small study areas. The Institute for Marine Mammal Studies (IMMS) has embarked on a historically significant study that covers a nearly 3,000 km² area and has identified over 2,600 individual dolphins. Photo identification has been used since 2010 to conduct mark-recapture studies on dolphins in the Mississippi Sound, Lake Borgne, and the Biloxi Marshes to better understand how the ecosystem has shifted in response to major events. This ongoing, long-term data set comprises hundreds of thousands of photographs of thousands of individual encounters and has produced significant results concerning site fidelity, reproduction, and disease caused by anthropogenic change. Our team continues to expand this data set, as well as discover new attributes of the largest population of common bottlenose dolphins in the United States. Along with each encounter, we take a variety of water quality parameters, including temperature, salinity, dissolved oxygen and pH to better understand suitable dolphin habitats within the Mississippi Sound. Our current work is focused on understanding dolphin social structure and spatial habitat use. As a bio-indicator species, the common bottlenose dolphin acts as a signal for overall environmental health. The success of dolphins is directly related to the health of the surrounding ecosystem, allowing us to monitor the ecosystem as a whole through their presence. By monitoring the health of bottlenose dolphins in the Mississippi Sound, we can identify issues within the broader environment and help to solve them in real-time.

Understanding reproductive patterns is important for understanding a population's viability and its trajectory. Reproduction is a good indicator of the health of the population and the supporting environment. The measurement of typical reproduction numbers (fecundity, inter-birth interval) depend on a relatively small population with reliable and regular sightings and are often reported with relatively short-term data. However, the Institute for Marine Mammal Studies' Mississippi Sound study site covers 2966 km2, with a large dolphin population resulting in a low recapture rate, making quick acquisition of these data difficult, if not impossible. Over our 13 year study period, 168 mother-calf pairs were identified with 13 mothers recorded with multiple calves. The range of inter-birth intervals for multi-calf mothers was 1.08-8.08 years, a wider range than is usually reported, and our calculated fecundity rate was an exceedingly low 0.024. 
However, our extensive database allowed for other reproductive measures. For example, a clear pattern of seasonal births was recorded, with a peak in the spring and summer months. There were also spatial hot spots with clusters of calves recorded on the western tips of the Mississippi Sound's barrier islands as well as the eastern portion of the sound, suggesting there might be preferred calving areas. We could also measure the correlation of reproductive rates in response to large environmental events such as the 2011 deep-water horizon oil spill and the 2019 opening of the freshwater Bonnet-Carre spillway. The spill resulted in a large increase in calf mortality and the spillway opening resulted in a large increase in adult female mortality. In both cases, reproduction rebound was not recorded until a minimum of 2 years post event. These findings underline the importance of long-term data for accurate reporting of reproductive data in any population.

As part of the ongoing Institute for Marine Mammal Studies (IMMS) Photo-Identification project, common bottlenose dolphins (Tursiops truncatus) in the Mississippi Sound, Lake Borgne, and Biloxi Marsh are photographed and analyzed to document health indicators within the population and to help capture the consequences of major environmental events. In 2019, the Bonnet Carré Spillway (BCS) was opened, and approximately ten trillion gallons of Mississippi River water was dumped into Lake Pontchartrain, eventually flowing into the Mississippi Sound. The Mississippi River is known to bring pollutants from the States through which it flows, creating a dead zone once the river water drains in the Gulf, but these waters are also freshwater, which can have major effects on the marine environment. Subsequent to the BCS opening, routine field surveys by IMMS recorded average salinity in the area falling drastically, from approximately 17 ppt in November 2018 to as low as 3 ppt, resulting in a rise in the number of freshwater lesions recorded in the local dolphins. Additionally, increased dolphin mortalities in the northern Gulf prompted the National Oceanic and Atmospheric Administration (NOAA) to declare an Unusual Mortality Event (UME) due to increased freshwater incursion into the region. Mississippi had the highest number of strandings reported with 153, three times the yearly average. Many of these animals showed signs of freshwater toxicity. The Mississippi River does not naturally flow into the Mississippi Sound, meaning the opening of the BCS, and the introduction of the low-salinity water, created new anthropogenic threats to the ecosystem. The declining health IMMS monitored in 2019 in dolphins, an indicator species, mirrored a fisheries disaster that occurred at the same time. Understanding the impacts of polluted freshwater on dolphins may help in the management of spillways and diversions to better conserve vulnerable coastal regions.

The Kemp's ridley (Lepidochelys kempii) is the most endangered species of sea turtle in the world. Juveniles and adults of this species have been widely documented in the Mississippi Sound and northern Gulf of Mexico through stranding data and incidental captures. From 2010-2013, the Institute for Marine Mammal Studies (IMMS) applied platform terminal transmitters (PTTs) to thirty-five Kemp's ridley sea turtles that were successfully rehabilitated at its facility. Multiple publications produced from this data established that the Mississippi Sound is a critical habitat for these turtles. Additionally, the turtles exhibited site fidelity and seasonal migrations between the Mississippi Sound and coastal Louisiana waters. From 2014-2024, IMMS released twenty-one Kemp's ridleys with PTTs as a continuation of this study. Eight of these turtles were translocated to IMMS for rehabilitation after stranding in Massachusetts waters during the cold winter months. These large scale events produce hundreds of cold-stunned sea turtles annually that are moved to other facilities like IMMS for long-term care. Preliminary findings on this dataset indicate similar habitat usage and migration patterns, even among the "non-native" translocated cold-stuns. Prey availability, temperature, and other natural and anthropogenic factors are driving forces to these observed behaviors. One turtle stranded dead in Pass Christian 107 days after its release with the PTT still attached. The data was analyzed to determine the likely location of mortality. This satellite telemetry study is essential to not only document their survivability and movements but is also useful to indicate where sea turtle hotspots are occurring and at what time of year. This can be used to identify high risk zones for regulatory agencies and other potential sources of anthropogenic driven mortalities.

The scope of sea turtle nesting activity in Mississippi is relatively unknown due to a variety of factors: 1) the changing coastline of the mainland's artificial beaches due to erosion and subsequent restoration projects; 2) limited accessibility to the islands where most nesting occurs; and 3) lack of historical organized surveys due to personnel, funding, and interest. Since 2012, the Institute for Marine Mammal Studies (IMMS) has assisted its state and federal partners to document any reported sea turtle tracks and nests on the mainland, conducting the first state-wide survey of the mainland beaches in 2021. In 2022 and 2023, IMMS conducted daily surveys on Ship Island and documented other reported nests. Historical data indicates that Mississippi averages 0-15 nests annually all of which were presumed to be from loggerheads (Caretta caretta). Through photo documentation and genetic analysis, three Kemp's ridley (Lepidochelys kempii) nests were confirmed on Ship Island during 2022 and 2023. This was a significant finding as nesting in the northern Gulf of Mexico is rare for this species and has never been previously documented in Mississippi. Natural and anthropogenic drivers greatly affect nest success. Of the twenty-two nests documented between 2022 and 2023, tidal inundation was the most significant cause of increased mortality or nest failure. Some nests showed no signs of embryonic development indicating a possible lack of mates in the area. Artificial lights on the mainland caused significant hatchling disorientation even on Ship Island - twelve miles away from those light sources. IMMS aims to reach a better understanding of how much activity is occurring in Mississippi and how viable its beaches are for successful nesting. Current related projects include creating a thermal profile of Mississippi beaches and conducting genetic analysis on confirmed nests to identify species, unique individuals, and multiple paternity.

The Kemp's Ridley (Lepidochelys kempii) is a critically endangered species of sea turtle that primarily nests on beaches throughout the Gulf of Mexico. The Kemp's Ridley does not have genetic sex determination but has temperature-dependent sex determination (TSD). TSD is found in certain reptile species in which the sex of hatchlings is determined by the temperatures the eggs are incubated at. To evaluate the current and historic sex ratios of hatchling Kemp's Ridley, nest temperatures were monitored at the Kemp's major nesting beach: Rancho Nuevo, Mexico. At Rancho Nuevo, eggs were transplanted into a main egg corral (i.e., corral central) to be protected from environmental damage. As the nests were transplanted, data loggers were placed at mid-nest depth for select Kemp's Ridley nests in the corral to record incubation temperature. Utilizing an "Embryogrowth" R model (Girondot and Kaska, 2014), the sex ratios were evaluated using incubation temperatures. From 1998 - 2023 (n = 491), corral nets have been predicted to have a predominant female bias with a gradual increase in mean nest temperature (R-squared = 0.015, p = 0.391). Further, nests that were laid near the start (March and April) of the nesting season produced lower percentages of females than in the middle (May, June, and July) of the season. This female bias mirrors predicted global climate changes shifts towards warmer temperatures and is indicative to future Kemps Ridley generations that will continue to populate the Gulf of Mexico.