For now this is only a placeholder to share a notion that the arguments I’ve reviewed to date about the Rio Grande Silvery Minnow (RGSM) don’t appear to be logically consistent.

According to referrences [1] and [2] below:

The New Mexico Portion of the Upper Rio Grande (URG) has fish but the Texas portion does not.  Yet the restoration activities are limited to New Mexico.

A portion of the URG which routinely goes dry (near Sevilleta) has been cited as a key region for restoration, even as “Biologists have collected as many as 10,000 minnows on some days” [2].  This collection rate was achieved during a presumed epic drought.

Minnows need pools and eddies to spawn, and high flows are considered an unfriendly environment.  Yet the promotions that the fish are endangered appear to amplify when flows are lower under drier conditions, and accordingly when pools and slower moving waters are more ubiquitous.  That makes little sense because as noted in [1] those lower flow states are considered to be ideal conditions for the RGSM.

The literature appears to assert that low flows and diversion dams both prevent fish from traveling upstream.  Yet New Mexico is upstream from Texas, and all of the RGSMs are apparently only in New Mexico.  Moreover, the literature indicates that such dams do not prevent downstream migration of the fish, and clearly the Upper and Lower Rio Grande haven’t permanently dried up anywhere along its stretches.  Accordingly, what has been preventing the fish from reaching Texas?   And what was the basis for assertions that the species were once naturally abundant in Texas?  Fossils?  Or perhaps very prescient farmers and ranchers and other residents of the Texas areas from the 1950s who took an interest in the tiny finger sized species?

I’m on another learning curve so I’ll continue to read and ask questions.  As a hydrologist who studies the natural cycles of flows within the Rio Grande, I’m increasingly curious to know if the RGSM is a non-problem.  In other words, I wonder if the fish are perfectly fine, highly adapted to the volatile climate behavior of the Western US, and if their population patterns are something that humans don’t have a handle on yet.





Feature image adapted from Theodore Geisel’s One Fish Two Fish 1960 Random House

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