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Coastal Marine Mammal Stranding Assessments

This project began in October 2010 and is Ongoing

We are studying stranded marine mammals to determine causes of death, anthropogenic sources of mortality, contaminant loads, diseases processes, and life history traits. We are sharing these assessments with resource managers, the public, and groups using potentially harmful chemical contaminants in the coastal zone. The health of coastal marine mammal populations can tell us a lot about the health of our coastal oceans and potential health risks to humans.

Why We Care
Contaminant levels found in dolphin blubber tissue are at alarmingly high levels along U.S. southeast coastal waters. Similarly, the discovery of marine mammal diseases such as papillomas, hepatitis, influenza, herpes, and brucellosis is a major concern to coastal human populations. As human population densities increase in the coastal environment, the likelihood of increased disease and contaminant loads in marine mammals may serve as a warning of our coastal waters.

What We Are Doing
We are conducting biological, chemical, and demographic assessments of stranded marine mammals. We have also recently begun evaluating rapid test devices for domoic acid and pathogens in stranded marine mammals. Because contaminants can also affect reproduction, we have begun studying the potential shift in the age of sexual maturation in dolphins that may be affected by contaminants.

What We Are Finding
We are finding that as development encroaches into the estuaries, dolphin strandings, fishery entanglements, hook and line entanglements and ingestion, and marine debris entanglements and ingestion all increase. We have established that the crab pot fishery is a significant source of mortality for coastal dolphins. Although these studies focus on dolphin mortality, there is a social aspect from the fisher’s view in how interactions with dolphins are perceived and also an economic aspect in catch loss and gear destruction as a result of interaction with dolphins.

Next Steps
We will continue to monitor diseases of marine mammals and their potential risk to human health through assessments of stranded marine mammals. We will continue to provide samples for contaminant analyses and are collaborating with NOAA’s Oceans and Human Health Initiative program and the Medical University of South Carolina to determine thyroid and sex hormone levels on Georgia coastal dolphins that have been exposed to high levels of contaminants. To aid in this research we will also be developing age and growth curves by analyzing growth layer groups in dolphin teeth to determine age classes affected and developmental (stunted growth) issues suspected in this population. A study of bone density of dolphins from this population and other dolphin populations from the southeastern United States will be conducted in collaboration with MUSC and OHHI to determine effects of contaminants on bone growth and density.

We will be investigating the role of cold water anomalies and the effect on dolphin survival. The winters of 2001 and 2010 were very cold along the U.S. southeast coast, resulting in numerous fish kills, cold-stunned sea turtles, and high dolphin mortality. The reduced fish abundance made dolphins more susceptible to fishery interactions as they searched for alternative food resources.

We plan to conduct an acoustic study of the effects on dolphin distribution in a local river where bridge demolition and construction is to occur. This study will also provide baseline data on noise before, during, and after construction. Marine mammals live in an environment where hearing is imperative for communication and foraging. Recent studies have suggested that a large percentage of live stranded animals are deaf because of increased noise levels in our oceans.

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