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Thousands of Rio Grande silvery minnows were released into the river this week after several months of tender, loving care at the Albuquerque BioPark.
Crews launched 42,000 of the fish into the Rio Grande through a large tube as part of the facility’s endangered species recovery efforts.
Kathy Lang, the BioPark’s aquatic conservation and operations manager, said each 1.5-inch-long fish was injected with a visible mark just under the skin.
“The marks are for folks doing surveys in the river tracking the minnow population,” Lang said. “If they were to catch a whole bunch of fish, but they were hatchery fish, that wouldn’t necessarily show how the natural population in the river is recovering.”
The team released 14,000 fish each at the Central Bridge in Albuquerque, the north boundary of Bosque del Apache National Wildlife Refuge, and a site near Jarales, south of Belen.
Aquatic biologists collected the fish as eggs from the river in the spring.
Eggs were distributed between the BioPark, a U.S. Fish and Wildlife hatchery in Dexter, and the Los Lunas silvery minnow refugium.
“You don’t want all your eggs in one basket, so to speak,” Lang said. “The early life stages are the most critical.”
Minnow habitat at the BioPark hatchery mimics ideal natural conditions so that as many fish as possible can survive to produce more minnows.
“As they age, we put them in outdoor tanks, which have more selection of natural foods like algae,” Lang said. “Slowly we get them away from being so dependent on human care.”
Fish and Wildlife determines the river locations where wild minnow populations need a boost from hatchery fish.
Silvery minnows were listed as endangered in 1994.
The fish was once found in Colorado, New Mexico and Texas. But now the tiny fish occupy a smaller habitat range from Cochiti Pueblo to Elephant Butte Reservoir.
Theresa Davis is a Report for America corps member covering water and the environment for the Albuquerque Journal.