The Iowa Department of Natural Resources discovered two pallid sturgeon for the first time in the lower Des Moines River earlier this year. The ancient fish is considered one of the rarest and most endangered species in North America.
Mark Flammang, an Iowa DNR fisheries management biologist, said pallid sturgeon are not well documented in the Upper Mississippi River above St. Louis, let alone in the Des Moines River.
“The bottom line is, this is very encouraging. We're very excited by this, but it's not the end of the road per se,” Flammang said. “There's a lot of work that has to be done."
The Iowa DNR identified the fish six days apart below the dam in Ottumwa during the agency’s annual sturgeon fish survey this spring. Since 2014, only shovelnose sturgeon and an occasional lake sturgeon have been identified.
“The interesting part about the fish that we collected in the Des Moines River is that these are wild fish,” Flammang said. “We were able to take a tissue sample and get genetic testing done, and so not only are they pallid sturgeon, but they're wild pallid sturgeon, which are extremely rare.”
Nine out of 10 pallid sturgeon collected from the Iowa section of the Missouri River were originally stocked from a hatchery, according to an Iowa DNR news release.
Flammang said the two pallid sturgeon found in the lower Des Moines River were over 30 inches long. But they can exceed 6 feet. Flammang said the Iowa DNR could not determine the sex of the fish.
“That might have something to do with the fact that even though they were relatively large compared to shovelnose sturgeon, they are still relatively young, and relatively young means decades,” he said.
Female pallid sturgeon don’t reach reproductive maturity until 15-20 years of age.
Increased river flows in the spring and corresponding temperatures cue pallid sturgeon to move upstream to find suitable spawning habitat, Flammang said. If successful, the larvae can drift downstream for hundreds of miles.
“Those young fish are just drifting down with the flow … and getting little bits of pieces of food as they move along,” Flammang said. “Then they just continue to grow until they become stronger and are able to swim against currents.”
The pallid sturgeon’s historic range includes the upper extent of the Missouri River down to the Gulf of Mexico. Habitat loss and fragmentation caused by dams contributed to declining numbers. Pallid sturgeon were added to the federal endangered species list in 1990.
While it’s illegal to kill pallid sturgeon, anglers in Iowa can catch and harvest shovelnose sturgeon.
“We want to make sure that anglers are equipped to tell the difference,” Flammang said. “I just urge anglers that are going to be fishing in the Des Moines River, and maybe even larger tributaries that are coming off any pool of the Upper Mississippi River, to be on the lookout. Don't just blindly assume that it's a shovelnose sturgeon.”
Pallid sturgeon are paler than shovelnose sturgeon and tend to have longer noses. They also have smoother bellies and different barbels, which are whisker-like sensory organs.
Flammang encourages anglers to contact the Iowa DNR if they find a pallid sturgeon.
He said future efforts to support the rare fish include more data collection and potentially habitat improvements in the lower Des Moines River. This could benefit species beyond pallid sturgeon, including shovelnose sturgeon.
Periods of low river flows and high temperatures over the last three decades contributed to extensive shovelnose sturgeon fish kills, Flammang said. It's what prompted the Iowa DNR's annual sampling in the Des Moines River.
