In early October, two graduate students from New Mexico State University plunge into the icy current of Leandro Creek. The small waterway flows through the 550,000 acre Vermejo park ranch, a reserve in the Sangre de Cristo Mountains, and the pair are looking for an unusual fish.
Kelsie Field, a 25-year-old from the Department of Wildlife and Ecology, carries two eight-gallon buckets, one full of water, the other of scientific gear, and wears a pair of grey waders. Michael Miller has a backpack with a battery attached to a metal detector.
Kelsie Field and Michael Miller are in New Mexico. Jeremy Miller is pictured.
Miller dips the detector into the creek and then squeezes the handle to send a small amount of electricity through the water. While the team's rubber boots insulate them from the shock, the resident fish are stunned and drift to the surface just long enough for Miller to net them and deposit them in the bucket. Most measure about 10 inches, though some are no larger than a little finger and a few stretch to 16 inches or more.
There are two species here. The Rio Grande cutthroat trout is distinguished by its cream-colored skin, black spots and orange slash under the jaw. It used to be widely distributed in rivers and streams across northern New Mexico and southern Colorado. In the case of Leandro Creek, it is reeling under the pressures of the climate crisis, habitat loss and hardy invaders.
Miller is at the park ranch. Jeremy Miller is pictured.
The brook trout is the most prolific species in Miller's net. The smaller brookies are sleek and silvery, while the adults have red and blue spots on their sides and an orange belly.
It's not clear how this interloper from eastern North America got here, but it was part of a human-aided diaspora that released brook trout into high-altitude lakes and creek across the west. The brookies have wreaked havoc on native trout such as bull, rainbow, California golden, and cutthroat, which they out-compete, as well as other aquatic organisms, including frog and salamanders.
The advantage of brook trout over other species is their rapid sexual maturation. The photograph is from the NPL.
Nearly every brookie the team captures is a male. Many of them are lab-produced brook trout. They have no X chromosomes to pass on, and they only have two copies of the Y chromosome that codes maleness. The population of brook trout will stop breeding and die out on their own eventually if the streams are stocked with this strain. Similar efforts are under way in a few of the creeks in Idaho, Washington and Oregon, and Nevada plans to embark on its own stocking programme this summer.
The chemical rotenone is the main tool to eliminate fish species. Colleen Caldwell is a professor of fish and wildlife at New Mexico State University and is overseeing the Leandro Creek project.
Researchers are still trying to understand if Trojan trout can thrive in their new environment and convince females to breed with them, as well as whether they can thrive enough in their new environment to tip the scales in the Rio Grande cutthroats favour. The hope is that the imposters will remove brookies from the stream systems without the need to use chemical agents.
The cutthroat was caught from the stream. Jeremy Miller is pictured.
Despite the method's promise, it raises questions about ethics and unforeseen outcomes.
There are clear streams in the mountains of northern New Mexico. There is a photograph of Christina Selby.
It's a good problem to have brook trout. They live in clean, cold water, so their presence indicates a waterway that is not polluted. They were confined to waterways at the margins of glaciers, which extended deep into the interior of North America. The species spread throughout the Great Lakes and the Canadian interior. The Mississippi River stopped their spread because it was warm.
It was newly arrived Europeans who helped them cross that barrier. brook trout were planted in streams and lakes. The railways filled their fish cars with eastern species, including striped bass, brown trout and brook trout.
The process of accretion was accelerated in the late 19th century by the belief that introduced species improved ecological conditions.
brook and cutthroat trout can be found in the Trampas Lakes in New Mexico. There is a photograph of Christina Selby.
The brook trout is a destructive force. The Environmental Protection Agency says 42% of the species in the US have been significantly impacted by invaders. Invasives are implicated in 70% of extinctions among aquatic species.
The brook trout that live in Leandro Creek were made at the Hayspur Fish Hatchery. Dan Schill, a retired fish biologist from the Idaho Department of Fish and Game, started the programme in 2008 at a different Idaho hatchery after hearing a presentation at a conference about theTrojan Y chromosome approach.
trays of eggs await shipping across the country as fish culturist Tom Lindenmuth oversees operations at the Hayspur hatchery in Idaho. Photographs by Jeremy Miller.
There are dozens of blue cyndrical tanks with male brook trout inside, which look like tiny brine shrimp with their egg sacs still attached. When the fish are ready to eat, attendants give them food coated with estradiol, a form of the female hormone oestrogen. The estradiol turns the testes of the male fish into ovaries, and the genetically male fish are capable of laying eggs.
25% of the offspring will be female with two X chromosomes, but 25% will be males with two Y chromosomes, which is the key to the genetic population control scheme. Estradiol will cause some of the YYs to form ovaries and produce eggs. The YY fish are crossed with YY males to create the broodstock. The streams will be home to the other YYs. brook trout will produce 100% male offspring if they fertilise the eggs of wild female brook trout.
There are rows of cabinets filled with small trays containing hundreds of brook trout eggs laid by a single male. The eggs will be treated with Ovadine, a chemical that strengthens their shells for shipping, according to a fish culturist and manager. They will be packed in wet paper towels and ice and sent to hatcheries in Washington, Oregon, Nevada and New Mexico.
A few brook trout eggs are being collected by Tom. Jeremy Miller is pictured.
The hatchery uses a sophisticated water recycling system to keep estradiol out of waterways. The fish exposed to estradiol never leave the hatchery, so there is no danger that they will harm the waterways or the fishers who catch and eat them.
The team has counted over half of the fish at the Vermejo reserve. Field makes a quick grab of one of the fish with a scanning device. This indicates that the fish has a tag larger than a grain of rice that contains information about when the fish was hatched and when it was released. Miller inspects the fish quickly, sliding thumb and index finger along its underside, which produces a spurt of milt, a substance containing sperm. He noted the missing fin, which was clipped by workers at another hatchery months earlier, as a clear sign that this is aTrojan.
Kelsie Field and Michael Miller are in New Mexico and are working on a project. Photographs by Jeremy Miller.
By the end of the second spawning season in 2020, 75% of the fish captured in Leandro Creek were male, and almost 30% of the juvenile fish from test streams around Vermejo were the male offspring of YY brook trout. Miller hopes the percentages will go up this year.
Genetically modified organisms and their potential to harm native species is a heated debate. Schill says that scientists haven't inserted any foreign genes into the trout's genes. That makes them different from a genetically modified animal.
Ron Sandler, a professor of philosophy at Northeastern University who specializes in bioethics, says that chemical altering an organisms is not a radical departure from the kinds of things that are being done. It is less radical than assisted evolution, where novel genes are inserted to make creatures better suited to cope with human-altered environments.
The ethics of releasing lab-produced trout into the wild are questioned by some biologists. Jeremy Miller is pictured.
The approach being taken with the Trojan trout is blithely treating the alteration and potential suffering of animals.
There may be unforeseen consequences from using rapidly reproducing, modified non-native animals as a form of biological control.
The cane toad was brought from Central and South America to Australia in 1935 to help with native beetles that were decimating the country's sugarcane fields. In large numbers, the toads devoured and poisoned the endemic lizards, snakes, and birds. Australia has a population of 200 million cane toads.
The best hope for native trout species may be the Trojan brook trout. Jeremy Miller is pictured.
Schill doesn't believe in the possibility of a disaster at Vermejo. brook trout have colonised the streams where the new strain is being introduced. Some natural and human-made barriers prevent the streams from leaving the study area. Since brook trout and cutthroat trout can't breed with one another, there is no risk of creating a hybrid.
Some biologists are concerned about the release of YY brook trout into Idaho streams. The bull trout and brook trout are related and can produce hybrid offspring.
By the time Miller and Field finish their work at Leandro Creek, a pattern has emerged: the brookies appear to be thriving and the cutthroat, though fewer in number, are holding their own.
If predictions hold, brook trout reproduction could cease and Rio Grande cutthroat populations could return to the stream. He says that we can fix our mistakes in other places.
We have an ethical responsibility to restore that natural history.
The patterns and colors of a male brook trout. The photograph is from the NPL.
A longer version of this story was published in bioGraphic, an independent magazine about nature.
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