The Crestone Eagle, February 2006:

New population of endangered Rio Grande sucker found in Crestone Creek
óColo. Division of Wildlife

Colorado Division of Wildlife (DOW) aquatic biologists received a surprise gift early last fall: a previously unknown population of the Rio Grande sucker was found in the San Luis Valley.

The discovery is significant because it will boost the DOW’s ongoing effort to develop self-sustaining populations of the fish in the Rio Grande drainage. The fish is listed as endangered by Colorado, and the federal government keeps the fish on its species watch list. One of the aims of the DOW is to assure that the sucker thrives in the valley and is not listed as an endangered species by the U.S. Fish and Wildlife Service.

“This is a significant find for our recovery plan,” said John Alves, aquatic biologist for the DOW in the San Luis Valley. “This doubles the number of our reproducing populations from one to two.”

The goal of the recovery program is to establish three populations in the Rio Grande drainage, one for each of the three major river drainages—Rio Grande, Conejos and the Closed Basin.

The Rio Grande sucker once thrived in creeks and rivers at elevations from 7,000 feet to 9,000 feet through- -out the San Luis Valley. Habitat loss due to dewatering of streams for irrigation, degraded water quality and introduction of non-native fish led to the demise of Rio Grande sucker in Colorado.

In the mid 1980s a population was discovered in Hot Creek, west of La Jara. The new population was found in Crestone Creek, which is located on the Baca National Wildlife Refuge. The small, shallow creek starts high in the peaks of the Sangre de Cristo range and eventually disappears into sand on the valley floor.

The wildlife refuge, which abuts Great Sand Dunes National Park, was established in 2003. The federal government and conservation agencies bought the land from a cattle company. Before establishment of the refuge only limited fish surveys were completed on the property.

Late in 2004, Alves received a call from the wildlife refuge manager who asked him to look at some fish workers had found in Crestone Creek. Those fish were Rio Grande chubs, also a rare, native species. Knowing that chubs and suckers prefer similar water, Alves explored the stream by electro-fishing in October 2005. Electro-fishing allows biologists to set a mild electrical charge in the water that temporarily stuns the fish and allows collection of specimens.

“I was surprised. As soon as I saw it I knew it was a Rio Grande sucker,” Alves said.

The stream is isolated—an important factor for maintaining a population. It’s unlikely that non-native fish have ever been in the waterway, so Alves is reasonably certain that the fish is a genetically pure strain. To be sure, he’s sent the fish samples to a lab in New Mexico for genetic testing. The results will be known in about six months.

“Whenever we can we want to recreate the native fishery. Those fish are best adapted to survive in the Rio Grande drainage,” he said.

Since 1994, the DOW has obtained Rio Grande suckers from the state of New Mexico and stocked them in eight streams throughout the valley. Another self-sustaining population has yet to be established.

Alves is hopeful that spawn from the new population can be used to start a brood stock. Eggs would be fertilized at the Native Aquatic Species Restoration hatchery in Alamosa, and the fish would be raised in captivity. After several generations are grown at the hatchery, fingerlings would be released in area streams.

It is difficult, however, to raise this species of sucker in a hatchery. Alves said developing a process could take a few years. Even if a brood stock is developed, biologists will face continuing challenges to get the fish into local waters.

“The hardest part of the whole program is finding candidate streams for reintroduction. Most of the streams have been disturbed by the introduction of non-native fish, and many streams are dewatered during the irrigation season,” Alves said.

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