They are unique in that they carry not one, but two copies of the Y chromosome that codes maleness they have no X chromosome to pass on. That’s because many are a lab-produced variety known as “Trojan” brook trout. Brook trout may greatly outnumber the Rio Grande cutthroat here, in some stretches by more than five to one, but nearly every single one of the brookies the crew captures is male. There, brookies’ voracious appetites and rapid sexual maturation have spelled trouble not only for native trout like bull, rainbow, California golden, and cutthroat, which they outcompete, but also for a host of other aquatic organisms, including frogs and salamanders.Īs Miller and Field shock and scoop their way upcreek, though, a pattern that could be the key to Leandro Creek’s salvation becomes apparent.
How this beautiful interloper from eastern North America got to this place is unclear, beyond that it was part of a human-aided diaspora that loosed brook trout into high-altitude lakes and creeks across the West, from northwest Washington to southern New Mexico. The fish’s colors are otherworldly, as if they have somehow absorbed into the riotous canvas of their skin the ragged beauty of the place in which they live. The adults, though, wear their spawning finery, their sides a riot of red and blue spots, their bellies orange as a ripe mandarin. The smaller “brookies” are sleek and silvery.
Which brings us to the more prolific species writhing in Miller’s net-the brook trout ( Salvelinus fontinalis). And like others among the dozen or so subspecies of cutthroat trout in the western United States, today it’s reeling under the pressures of climate change, habitat loss, and-in the case of Leandro Creek-a hardy intruder. Once widely distributed in rivers and streams across northern New Mexico and southern Colorado, the Rio Grande cutthroat is now found across a mere 10 percent of its historical range. One is an embattled native, the Rio Grande cutthroat trout ( Oncorhynchus clarki virginalis), distinguished by its cream-colored skin, mottling of black spots and a vibrant orange slash under the jaw. Occasionally, though, Miller’s handle bends sharply as he nets a hunchbacked specimen of 16 inches or more-apex predators gorged on smaller fish, in this waterway scarcely wider than a city sidewalk. Stunned, they drift to the surface just long enough for Miller to net them and deposit them in Field’s bucket. While the crew’s rubber boots insulate them from the shock, the resident fish are exposed to the electrical current. This, Miller dips into the creek, squeezing the handle to send some 300 volts through the water.
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