SOUTH MISSISSIPPI (WLOX) - The Mississippi Sound is home to one of the largest populations of bottlenose dolphins in the world.
The mammals have faced serious challenges in recent years; everything from the BP oil spill, to red tide, to harmful pollution runoff from the Mississippi River.
But with frequent strandings and ongoing threats to the environment, how healthy are the dolphins in Mississippi?
WLOX News Now recently spent time with scientists at the Institute for Marine Mammal Studies, who are working to address many of the unanswered questions about the health of the playful marine mammals.
Veterinarian, Dr. Debra Moore, performs regular physical exams on the captive dolphins at IMMS. Having access to the animals in captivity provides a great resource for better understanding the life and health of dolphins.
"One of the things that we do here is we are constantly looking at their health status, and they help us understand what's happening with the wild populations. If we didn't have this, we would just have a snippet of what's happening in the wild," said Moore. "When they're in captivity, we're able to check them physically. And we do this every month. We do a physical exam on them," she explained, "We check all the vital organs, we take blood from them."
Unlike the captive animals, dolphins in the wild have faced some significant health threats in recent years.
"We've had some serious issues medically with them. They've been challenged with the oil spill, they've been challenged with red tides that happened, they're challenged from the Mississippi River, from the runoff from all the states that are above us. And it takes a toll on their health," said Moore.
Dr. Eric Pulis is a marine conservation ecologist at IMMS.
"This year we saw an increase in strandings over the last...couple of years, and still trying to get exactly what's going on in the population," Pulis said. "We saw an increase in 2010 and 11. And then it decreased to 40 or 50 a year for a few years, and then we saw a spike again this year, up to about 80," said Dr. Pulis.
The dolphin strandings in Mississippi make up about 30 percent of the total strandings in the northern Gulf of Mexico. Although the BP oil spill and red tide have both been linked to dolphin deaths in recent years; many questions remain.
"It could be absolutely anything. There's going to be some that might be old age. Some that may have had some sort of interaction with something," said Dr. Pulis, "Absolutely disease. You know, you have an epidemic come through and a few of the animals succumb to that."
We joined the research team on a recent field trip into the Mississippi Sound.
"We're interested in the things that impact their survival. They are a sentinel species of this environment, so they eat the same fish we eat, they swim in the same water we swim in. We want to know whether or not they're healthy because it gives us a good idea if the entire environment here is healthy," said research scientist Dr. Mystera Samuelson.
The latest estimate from NOAA says the dolphin population in the Mississippi Sound is around 900 to 1,000 animals. One of the main objectives on such trips is to get good photographs of the dolphin's dorsal fin.
"We use photographs, as you saw us taking pictures of their dorsal fins. The dorsal fins act almost like a fingerprint. Dorsal fins are very unique, they get scars and notches that does allow us to differentiate individuals," said Dr. Samuelson.
Collecting data from the spot the dolphins are spotted, is also critical. A special underwater microphone measures the sounds of the dolphins.
"We hear things like the use of signature whistles both to find their groups, but we also hear that in times of distress, possibly to call in other animals to help them out," said Dr. Samuelson.
Dolphin dorsal images captured at sea are later run through a special computer program that compares them with thousands of others.
IMMS researchers say while it's important to assess the overall health of the dolphin population, it's even more critical to track health long-term.
"That's really the important thing that we want to stress here with IMMS. We do the research and we want it to continue for a prolonged period of time because we want to follow these animals for generations," said Dr. Moore.