Tracking eel movements reveals their habitat and life cycles.
Missouri Department of Conservation (MDC) resource scientists recently tracked an American eel on what they called an extreme long distance migration of 688 river miles.
The eel was one of 20 eels implanted with transmitters by MDC scientists working on a special project to identify American eel habitat and movement patterns.
“American eels have a unique life cycle which requires long migrations to complete,” said Andy Bueltmann, a Southeast Missouri State University graduate student working on the project.
In Missouri, American eels are mainly located in the Mississippi River, but little information exists about the habitats they use, what they eat and where the eels travel within the big river. This is why scientists with the MDC’s Big Rivers and Wetlands Field Station in Jackson began the tracking study in 2014, implanting 20 eels near Cape Girardeau.
Eel number 13038 was implanted and released April 14, 2015. Five months after release, Sept. 21, the eel was detected by U.S. Army Corps of Engineer researchers near the Gulf of Mexico, 688 river miles south of the release site and about 300 miles north of the Gulf of Mexico.
“This detection most likely signifies that Eel 13038 was migrating back to the Sargasso Sea for spawning purposes,” Bueltmann said. “Overall, this is an interesting piece of information which helps us better understand American eels in the Mississippi River.”
The Sargasso Sea, located in the North Atlantic Ocean, is where American eels begin their life cycle. After hatching in the Sargasso Sea, they drift along oceanic currents until they reach the continental coast, Bueltmann said. Then, they either move up into freshwater like the Mississippi River or remain in waters near the Gulf Coast while they grow.
“We think the [American] eels that enter the freshwater rivers are all female, while the males remain along the continental coast,” Bueltmann said. “After they grow to a certain size, they mature and begin to migrate back to the Sargasso Sea, like it seems this eel was doing.”
Bueltmann said after the adult eels return to spawn in the Sargasso Sea, they die, leaving the next generation to continue the cycle.
“Knowing where the eels go helps us to identify their habitat needs and the overall health of our big river habitat,” Bueltmann said.