On Aug. 25, the New Mexico Game Commission will decide whether to release fish-killing poison into a Rio Grande tributary—all with the ironic goal of protecting the state fish.

The commission will vote on whether to use a piscicide (pronounced PISK-icide) to kill nonnative fish currently living in Las Animas Creek, near Truth or Consequences. The measure may be an important step in the effort to keep the native Rio Grande cutthroat trout—also the New Mexico state fish—from becoming listed under the Endangered Species Act. But it also means killing all the fish and insects in the treated section of the stream with an undiscriminating poison.

The piscicide rotenone enters fish' systems through their gills and stops their cells from converting energy for their use, causing paralysis and death. A few minutes after its application, the poison is chemically neutralized so it doesn't flow downstream and affect other reaches. Physical barriers are erected upstream so that nonnative fish can't repopulate the area.

Nonnative fish can displace native trout by moving into their habitat. Nonnative species that are sufficiently similar to the Rio Grande cutthroat, such as rainbow trout, dilute the native stock's genes by breeding with them to produce a hybrid trout.

Las Animas Creek is part of the Rio Grande cutthroat's natural habitat, and the rotenone treatments can be expected to kill some of the species they're aimed to save before the stream is restocked with native fish from a hatchery.

Currently, Rio Grande cutthroats aren't listed as endangered or threatened, but they are estimated to be present in only 10 percent of their historical habitat, which is mostly in New Mexico and southern Colorado. The project would treat portions of 40-mile Las Animas Creek, which lies partly on National Forest Service land and partly on media mogul Ted Turner's 210,000-acre Ladder Ranch.

One of two other ongoing piscicide projects in New Mexico is underway at Turner's Vermejo Park Ranch near Raton, where Turner Enterprises lead biologist Carter Kruse says 14 miles of the Rio Grande cutthroat's habitat has been restored so far using rotenone. New Mexico Fish and Wildlife Conservation Office Project Director Jim Brooks touts another rotenone success: The native New Mexico Gila trout was taken off the threatened species list after 20 miles of its habitat on the west fork of the Gila River was restored.

Turner's camp and New Mexico Game and Fish have been interested in treating Las Animas Creek for about the past 10 years, but the project has always run into snags, Kruse says.

"There's been a lot of hesitancy about 'How effective are these projects? What are you trying to do? Are there chemicals left over in the water?'" Kruse says. "So the [Game Commission] just started to be very cautious in their approval of the project…I think the climate has become more favorable, but there are still some people philosophically opposed, just like they are to spraying weeds or application of any chemical in the environment."

Former Game Commissioner Dutch Salmon, a vocal opponent of piscicide use, was instrumental in postponing the project. So was WildEarth Guardians (at that time known as Forest Guardians) founder Sam Hitt, who believes the negative effects of the project far outweigh the positives.

"This is a very important stream that's in very good condition…the last thing you want to do with a high-quality stream like this is to kill everything, and that's what they're going to do," Hitt says.

Although insects killed by rotenone repopulate quickly, according to state Game and Fish fisheries Chief Mike Sloane, there are more concerns regarding a threatened native frog species. Although Brooks says the amount of rotenone needed to kill a leopard frog is about 50 times higher than the concentration used to treat the streams, as a precaution, biologists had to search the river for any tadpoles or adult frogs before beginning the west Gila treatment, Brooks says. Kruse confirms leopard frogs live on the upper Las Animas, and similar precautions would have to be taken there.

WildEarth Guardians Wild Places Program Director Bryan Bird says that, although his organization doesn't reject the idea of any rotenone use, it is concerned about correct execution of the project and believes the poison should be applied only once per area. The Las Animas project is expected to take at least two applications, as one application typically doesn't kill every fish in a stream. In addition, Bird believes it's important to address the underlying issues of habitat degradation and to keep nonnative fish from being accidentally restocked.

"[Game and Fish] often make[s] blunders that negate the whole thing," Taos fishing guide and owner of Taos Fly Shop Taylor Streit says. Streit, who has closely followed the Vermejo Park Ranch project, says that, during that project, nonnative rainbow trout were actually put back into treated areas—a risk if projects aren't carefully controlled and protected.

Hitt says there's nothing inherently wrong with "hybrid" versions of Rio Grande cutthroat that may have some rainbow trout in their pedigree. The so-called hybrid fish are, he argues, just Rio Grande cutthroat specifically adapted to the part of the Rio Grande they inhabit, and are superior to the farm-raised Rio Grande cutthroat that would be replacing them.

"We're talking about a trout that looks like Rio Grande cutthroat, acts like Rio Grande cutthroat, and certainly has been in this stream in its current genetic configuration and seems to have adapted and thrived," Hitt says. "And we're talking about killing them all."

But to some, the end justifies the means. According to a recent article by national trout fisherman's group Trout Unlimited, Turner created one of the largest habitats in Montana for the native westslope cutthroat trout through the use of rotenone and antimycin, another piscicide, at his 113,000-acre Flying D Ranch.

New Mexico Council of Trout Unlimited Chairman William Schudlich confirms TU's support of the Las Animas plan. But for sportsmen, preservation of the Rio Grande cutthroat means not only protection of the species, but also prevention of the onerous restrictions that would come with an endangered species listing. Should Rio Grande cutthroat become listed as threatened, sport fishing of the species would be suspended, and cumbersome water and land use restrictions would be placed on all of its habitats.

"Everyone worries that the Endangered Species Act can close down an entire watershed to fishing or other use," Streit explains.

Although many sport fishermen were opposed to the Gila trout project, Kruse says public opinion in New Mexico seems to be shifting, as Montana's did.

"The transition New Mexico is going through, [Montana] went through a few years before," Kruse says. "They got past that initial 'Oh, my goodness, what are you doing?' type of reaction. We've done a lot of work in an attempt to answer questions that we thought were appropriately raised."

In an editorial in sportsmen's magazine Outdoors Unlimited, angler and writer Ted Williams argues that to fish for "junk" nonnative species is just a sport, while fishing for native fish represents a meaningful communion with nature. Though he might not go that far, Streit understands the draw of the New Mexico state fish: When he spoke with SFR for this story, he was winding his way along a road near Tres Piedras, in search of a remote stream where Rio Grande cutthroat are rumored to roam. He says that there's really no alternative to piscicide for getting rid of introduced and hybrid fish and making way for the real thing.

"The thing about fish poisoning is that it's the only—unfortunately, the only—thing that works to accomplish that goal," Streit says.