The history of the Trojan trout

This, Miller plunges into the stream, squeezing the handle to send some 300 volts through the water. While the crew’s rubber boots insulate them from the shock, the resident fish are exposed to the electrical current. Stunned, they drift to the surface just long enough for Miller to grab them and drop them into Field’s bucket. Most are around 10 inches. Some are no bigger than a little finger. Occasionally, however, Miller’s grip bends sharply when he catches a humpbacked specimen 16 inches or more – apex predators gorged on smaller fish, in this waterway barely wider than a city sidewalk.

There are only two species here. One is a crenellated native, the Rio Grande cutthroat trout (Oncorhynchus clarki virginalis), who is distinguished by her cream-colored skin, mottling of blackheads, and a bright orange barrette under her jawline. Once widely distributed in rivers and streams in northern New Mexico and southern Colorado, the Rio Grande cutthroat is now found in only 10% of its historic range. And like others of the dozen cutthroat trout subspecies in the western United States, it is now reeling from climate change, habitat loss and, in the case of Leandro Creek , of a robust intruder.

Which brings us to the most prolific species writhing in Miller’s net, the brook trout (Salvelinus fontinalis). The smaller “brookies” are elegant and silvery. The adults, however, wear their spawning finery, their sides a riot of red and blue spots, their bellies orange like a ripe tangerine. The colors of the fish are otherworldly, as if they have somehow absorbed into the tumultuous web of their skin the tattered beauty of where they live.

It is unclear how this handsome intruder from eastern North America arrived at this location, beyond that he was part of a diaspora assisted by the man who released the brook trout in high elevation lakes and creeks across the West, from northwest Washington to southern New Mexico. There, the voracious appetites and rapid sexual maturation of the brookies have caused problems not only for native trout such as bull, rainbow, California walleye and cutthroat, which they outnumber, but also to a host of other aquatic organisms, including frogs and salamanders.

As Miller and Field shock and move up the creek, a pattern that could be the key to Leandro Creek’s salvation becomes apparent. Brook trout can far outnumber the cutthroat of the Rio Grande here, in some stretches more than five to one, but nearly all of the brookies the crew catches are male.

That’s because many are a lab-produced variety known as “Trojan” brook trout. They are unique in that they carry not one, but two copies of the Y chromosome that codes for masculinity; they have no X chromosome to pass on. Unlike many creatures, including humans, fish can survive without X and seem unaffected by lack. And since 2018, Miller, the project’s principal investigator, and his predecessors have been conducting a bold new experiment, stocking various streams across the Vermejo Preserve with this strain in an attempt to skew the brook trout’s sex ratio. until now. the population will stop reproducing and go extinct on its own. Similar efforts are also underway in a handful of creeks in Idaho, Washington and Oregon, and Nevada plans to embark on its own seeding program this summer.

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