In the aftermath of the Deepwater Horizon (DWH) catastrophe, impacts to common bottlenose dolphins in heavily oiled coastal areas of the northern Gulf of Mexico were well documented by the Natural Resource Damage Assessment (NRDA). Among other health issues, a high incidence of reproductive failure was detected, although specific causes of the failures could not be determined during the NRDA studies. In Barataria Bay, Louisiana, which was heavily oiled, only 20% of pregnancies diagnosed via ultrasound during health assessments following the spill were observed subsequently to result in live calves, as compared to 83% for the Sarasota Bay reference population. The overall goal of this project, funded by the Gulf of Mexico Research Initiative (GoMRI), is to expand on the previous NRDA studies of dolphins in heavily oiled areas of the Gulf to understand the underlying factors involved in the observed reproductive failures.
We are using enhanced ultrasound techniques recently developed by NMMF veterinarians and employed for the care of dolphins managed by the U.S. Navy. We are employing the new ultrasound techniques to identify fetal and placental abnormalities in bottlenose dolphins in Barataria Bay. Over the past 2 years, we have evaluated 28 female dolphins in Barataria Bay and we are in the process of analyzing the diagnostic data and conducting photo-monitoring surveys to document the reproductive outcome of 11 pregnant dolphins. In addition to the enhanced ultrasound evaluation, we are using capnography to assess oxygenation, and collecting blood for hematological and serum biochemical analyses, as well as analysis for an extended suite of hormones. To add to the dataset, blood data from female dolphins previously sampled (2010-2014) in Barataria Bay, Mississippi Sound, MS and Sarasota Bay, FL with known pregnancy outcome were compiled, and banked serum samples have been analyzed for the extended suite of hormones. Analysis of the blood data from prior years shows that pregnant dolphins not seen subsequently with a live calf often have significantly elevated white blood cell counts and lower hemoglobin as compared to dolphins with successful outcomes. Our findings to date suggest that poor maternal health may be predictive of reproductive failure. Additional information on the project can be found on the GoMRI website.
This article appeared on page 5 of the 2018 SDRP Annual Report, Nicks n Notches.