Copyright © 2021 Albuquerque Journal
Tiny tracking devices inside tiny minnows could tell scientists a big story about how the fish move through a critical stretch of the Rio Grande.
A U.S. Fish and Wildlife Service crew tagged 5,000 Rio Grande silvery minnows last week at the Southwestern Native Aquatic Resources Recovery Center in Chaves County.
Tracking data from the minnows will inform a Utah State University study of how fish passages could be implemented at the San Acacia dam, north of Socorro, and Isleta dam, at Isleta Pueblo.
Thomas Archdeacon, fish biologist with the New Mexico Fish and Wildlife Conservation Office, said the study will track how the minnows move in relation to the dams and where they swim throughout the year.
“Some will likely be exposed to river drying,” he said. “Most of my research shows that the minnows don’t move out of that, and they just kind of get trapped. This data would be more of a smoking gun to show where the individual tagged fish go.”
The endangered species is often at the mercy of fluctuating flows and a fragmented river.
Fish passages, like the structure at Albuquerque’s Alameda dam, can help fish navigate a river obstructed by manmade diversions.
The passive integrated transponder tags implanted in the minnows are similar to microchips for a dog or cat.
Scientists made small incisions with scalpels and inserted each tag by hand. The federal hatchery also produced the minnows.
Fish needed to be at least 2 inches long to hold a transmitter, which is slightly bigger than a grain of rice.
Wagon wheel-sized data stations along the river will record when a tagged fish swims by with its individual tracking code.
“It can be surprising to see how far these little fish move sometimes,” Archdeacon said.
The Utah State team will also periodically float the river on a raft equipped with a scanner as part of the multiyear study, which was funded by the U.S. Bureau of Reclamation.
The fish biologist said the current outlook for the minnow “doesn’t look good” after an exceptionally meager spring runoff in 2020.
“After a good spring runoff we find a bunch of minnows when we do fish rescues,” Archdeacon said. “In years after bad spring runoff you find very few. In a bad year you see very few wild adults and very few fish that spawned this year. We might see a whole bunch of large hatchery fish from 2019, which we can identify by paint tags. But even if we added all those categories up, I’d say it will still be way fewer than in 2017 or 2019.”
Theresa Davis is a Report for America corps member covering water and the environment for the Albuquerque Journal.