While flathead chub is not threatened across its range, the Missouri Department of Conservation lists it as state endangered within Missouri. The state has yet to determine threats to this species in Missouri, but constructed dams are blamed for its decline in Colorado and Kansas.

Habitat Assessment and Monitoring crews recently caught a flathead chub in two separate trawls while conducting standard monitoring on the lower Missouri River.  Flathead chub was once one of the most common minnow species collected in seine hauls in the Missouri River within the state of Missouri.  However, during the early 1900’s six major dams were constructed on the Missouri River in the Dakotas and Montana, and the reach of river in Missouri was significantly channelized for flood protection and navigation.  Dams led to a nearly four fold drop in water turbidity and channelization practically eliminated the complex braiding nature of the river channel that created most shallow sandbar areas once used by this species.

Flathead chub is a unique species that was oddly adapted to live in the Big Muddy because it is a surface insectivore that likely relies heavily on vision to hunt and capture prey.  Such a large decrease in turbidity would seemingly benefit flathead chubs by increasing their range of vision for hunting.  However, flathead chubs in lower Missouri River have been extremely rare since the river was altered.  Our two specimens are significant because they represent half of the known flathead chubs caught since 1998.  Records are unclear, but there may have been as many as 20 caught in the last 25 years in lower reaches of the Big Muddy.  Instead, we suspect that decreased turbidity actually worked to nearly eliminate the flathead chub population in lower Missouri River.  Prey can likely see an approaching flathead chub in time to react and escape, and the chub’s tendency to hunt near the surface logically increases their vulnerability to other predators.  Clearer water may have led to reduced feeding efficiency and greater predation risk; both factors that would threaten populations of any organism.  

Work to rehabilitate habitats in the Big Muddy has begun to restore small pieces of river to mimic what we think it historically looked like.  Expansive sandy areas with shallow water and a few braided sandbars may provide the topology this fish likes, but until engineers can figure out how to restore historical water turbidity, flathead chub will likely not regain its numerical dominance in Missouri River seine hauls.  Though two specimens hardly signal a recovery, we are now more excited than ever to monitor the flathead chub population as habitats are restored towards the pre-channelization era.

Our diligence to monitor rare species illustrates our commitment to both the “Leadership in Science and Technology” and “Aquatic Habitat Conservation and Management” goals of the Fisheries Program’s Vision for the Future.