The reach of the Rio Grande that flows through Big Bend National Park will play an important role in recovering a native fish that has been absent from Texas waters for more than fifty years.
According to a rule published today in the Federal Register, the Rio Grande silvery minnow will be reintroduced into its namesake river under a provision of the Endangered Species Act that allows local communities greater flexibility in establishing parameters for reintroduction.
Approximately 500,000 Rio Grande silvery minnows will be placed into the river on Dec. 17.
The release supports the agencys plan to recover the rare minnow so that it no longer needs the protection of the Endangered Species Act.
Reintroduced minnows in the Texas reach of the river will be considered nonessential and experimental. The designation is allowed under section 10(j) of the ESA which encourages the reintroduction of a species by reducing regulations. "Using a nonessential, experimental designation ensures that the daily activities of water users and landowners are unaffected by the reintroduction," said Benjamin N. Tuggle, Southwest Regional Director for the Service. "Community leaders told us they were supportive of the reintroduction program but emphasized they needed to count on reliable flows and water delivery. We can satisfy both fish and human needs."
The Rio Grande silvery minnow is a small fish that was once one of the most abundant and widespread of the native fishes in the Rio Grande and Pecos River. It existed from northern New Mexico to the Gulf of Mexico in Texas. Today the endangered silvery minnow occupies only about five percent of its historic range in the middle Rio Grande in New Mexico. Throughout much of its historic range, the decline of the Rio Grande silvery minnow has been attributed to modification of the flow regime, channel drying, reservoirs and dams, stream channelization, decreasing water quality and perhaps interactions with non-native fish. During it various life stages, the silvery minnow uses low velocity habitats with a sandy and silty substrate associated with a meandering river that includes side channels, oxbows, and backwaters.
The Services preferred approach to recovering the Rio Grande silvery minnow is to create self-sustaining populations in at least three areas of its historic range. "The Big Bend reach has been identified as the area within the species historic range most likely to support an additional population," said Tuggle. "It is our first priority area for repopulation."
The monitoring program will contribute to existing data and will use statistically valid methods to assess changes in age-class structure structure
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Learn more about structure and abundance of Rio Grande silvery minnow and other fish. "After the initial stocking, we will monitor to see how the fish is faring and look for any spawning behavior or young-of-year fish that might be present," said Tuggle.
The Rio Grande from Little Box Canyon downstream of Ft. Quitman, Hudspeth County, through Big Bend National Park and the Rio Grande Wild and Scenic River, to Amistad and the Pecos River from its confluence with Independence Creek to its confluence with the Rio Grande, has been designated as a nonessential experimental population area. Although only portions contain suitable habitat, this area represents the maximum geographic extent to which the fish could move if released in the Big Bend stretch of the Rio Grande. Rio Grande silvery minnow will only be released in the Rio Grande and are not expected to move into the Pecos River.
The reintroduction project was first proposed in 2007. Todays final rule is available on the internet at www.fws.gov/southwest/es/AustinTexas. To request a paper copy or a compact disc, please call 512-490-0057, or write to Adam Zerrenner, Field Supervisor, Austin Ecological Services Field Office, 10711 Burnet Road, Suite 200, Austin, Texas, 78758.
