87: Plains Minnow

A tiny friend whose livelihood is threatened by dams

I write to you from Arapahoe, Ute, and Cheyenne land. I am interested in learning about the different animals that live in the place where I was born. Before we start with today’s animal, I want to emphasize that biological classification as understood by western society has its roots in racism, sexism, and transphobia – here’s a good explainer about why.

First, let’s look at this really cool map from “Colorado’s Little Fish” by John Woodling:

I love this map so much. It’s like a reverse topography of the state – the placement of high mountains are imagined in the spaces between the colorful lines. The Plains Minnow (Hybognathus placitus) is a rare species in Colorado, which is at the eastern edge of its range. It has been found on that dark green section of the South Platte River Basin to the east of Fort Morgan, in the very far east of the deep magenta of the Arkansas River Basin, and in the sky blue of the Republican River Basin. These are little guys, with a maximum length of 5 inches (130 mm). They live in schools of fish at the bottom of shallow river channels.

They are now considered endangered in Colorado and are threatened in other parts of their range. River damming and the subsequent absence of large flood mean tough conditions for the Plains Minnow. Why does river damming have this effect? From the source linked above:

“In streams with meandering channels, the elimination of natural flood cycles leads to a decrease in channel migration rate. This has lead to the reduction in growth of riparian areas in the northeastern portion of the Great Plains. The elimination of natural flood cycles leads to the narrowing of braided stream channels into straighter deeper channels. This has effectively eliminated the shifting sandbar/highly turbid habitat that should occur in this ecosystem. An observed result of this process has been observed as an encroachment on the historically shifting streambed by riparian vegetation in the southwest portion of the Great Plains (Friedman et al. 1998). The degradation of braided channel systems due to highly modified flow regimes (e.g., reduction of peak flows, flow stability, reduced

turbidity) in southwestern streams has contributed to the decline in plains minnow populations and possible extirpation from some drainages (i.e., Arkansas River Basin in Colorado).”

That chain of cause and effect is remarkable to me. Time to get rid of some dams!