The carcass of a dead bottlenose dolphin discovered near the U.S. 190 Mississippi River Bridge in Baton Rouge was recovered by state Department of Wildlife and Fisheries staff Wednesday afternoon, said Ashley Wethey, a department spokeswoman.
A hydrographic survey crew working in the river Monday found the dolphin, but weather and logistical difficulties made recovery of the carcass impossible until Wednesday.
The bottlenose dolphin primarily lives in coastal and offshore waters and it’s unclear how or why this particular saltwater mammal made it as far upriver as Baton Rouge, Wethey said.
It is unusual for dolphins to be found in rivers or freshwater environments, but it’s not unheard of, said Blair Mase, Southeast Marine Mammal Stranding Network coordinator for the National Oceanic and Atmospheric Administration Fisheries.
Since 2002, there were reports of 13 saltwater mammals found in rivers or lakes more than a mile from the Gulf of Mexico between Texas and Mississippi, with eight of those occurring in Louisiana.
Although it’s difficult to say what caused the dolphin to end up as far up the Mississippi River as Baton Rouge, there are theories.
“Sometimes it’s weather events. Sometimes, we just don’t know,” Mase said.
During hurricanes and tropical weather events, these animals will swim inshore and sometimes get stranded. After Hurricane Katrina, there were a number of strandings, including a dolphin found in a golf course pond and another one found in a ditch behind a high school, Mase said.
With Hurricane Isaac in August and the large storm surge associated with the storm, Mase said people in her organization were expecting quite a few reports of dolphins and other animals that were in places they aren’t normally found. However, she said, they didn’t receive that many reports of displaced saltwater mammals.
Although bottlenose dolphins are saltwater animals, they can survive in fresh water, but after awhile the freshwater starts impacting the animal’s health, Mase said. After a couple weeks, the bottlenose dolphin would have had skin lesions, eye problems and its endocrine system would have been impacted, she said.
“They end up getting over-hydrated,” Mase said. “Dolphins are not set up for that kind of thing.”