Thursday, April 28, 2011
We had dragged nets through numerous reaches of the Powder River, a tributary of the Yellowstone in southeastern Montana, capturing an incredible diversity of fishes, yet the sturgeon chub eluded us where a decade earlier they had been abundant. Then, on the last day and the final seine haul, the technician working the fish asked, “what the heck is this?”
Attracted by our high fives, victory dances, and cartwheels, a bystander came over to see our catch only to ask, “do they get any bigger?”
I paused my happy dance to consider the three-inch long, silvery fish in the bucket. “Nope, that one’s a trophy!”
The sturgeon chub is a small fish of big muddy rivers. It gets its common name from its bottom hugging mouth and elongated snout, not unlike those of a sturgeon. Also like sturgeon, the ventral position of its mouth allows it to glean invertebrates off of the streambed.
Living in rivers that sometimes have the consistency and clarity of chocolate cake batter, it relies more on sensory papillae, external sensory bumps on its body and fins, than its tiny eyes to find its way to a meal.
The sturgeon chub's keeled, or ridged, scales are features that distinguish it from other species of chub living in Montana’s prairie rivers.
The sturgeon chub's enormous historic range includes the Missouri and Mississippi rivers, and their larger tributaries. Dams, diversions, and other alterations along these big rivers have changed their habitat, and in some portions of their range, they are gone or critically imperiled.
In Montana, when biologists started to look for sturgeon chub they were found to be abundant in the Yellowstone River, and portions of the Missouri River that retain warm, turbid flows and gravelly substrate.
The Powder River was also a stronghold for sturgeon chub; however, recent sampling has documented a dramatic reduction in their numbers and distribution. No obvious causes have emerged to explain this decline. The Powder River is a free-flowing stream that lacks the developments associated with declines of sturgeon chub in other rivers.
Although my career path has moved away from prairie rivers, I still think fondly of this fish with the funny nose, and hope we can find ways to keep it around, especially in the Powder River.