While conducting field assessment during the Summer of 2015, a deceased aquatic species was found in an upper tributary of Walnut Creek by Polk SWCD and Dallas SWCD interns. Using images taken by staff, the DNR identified the species as a Chestnut Lamprey. Turns out, this lamprey has not been found in the Des Moines River basin since the 1890’s!
Chestnut Lampreys move into small tributaries during spawning. They search for rock habitat to lay their eggs in and then die. It is possible that the found lamprey had recently spawned and that is why it was found deceased. The eggs hatch into larvae that filter feed for several years in the small streams. The larvae then transform into parasitic adults and move downstream to feed on larger fish.
The larvae of the Chestnut Lamprey require clear, permanent flowing streams in order to survive the first few years of life. Due to high turbidity (or cloudiness) of most of the upper reaches of Walnut Creek, lamprey larvae have a hard time surviving. In 2013, a CREP wetland was installed along the tributary upstream of where the lamprey was discovered. This leads us to believe the wetland is doing its job cleaning the water, allowing lampreys to survive!
In partnership with the DNR, Polk SWCD have begun searching the tributaries of Walnut Creek for evidence of a population of Chestnut Lampreys. Unfortunately, no lampreys were found this year. We will continue out search next Spring!