Fish and Game seeks to improve alpine fishing with âsuper-buckâ brook trout
With its aggressive eating habits and spectacular colors – olive green back, white fins, splashing yellow and red spots surrounded by pale blue and fiery red bellies – brook trout are arguably one of the most attractive sport fish. in North America.
But although it is considered an iconic predator in its original range, i.e. fresh, well-oxygenated lakes and streams in the eastern United States and Canada , from northern Georgia to Hudson Bay, fish are an unwanted presence in the western United States.
That’s for two reasons, according to Gregg Anderson, Idaho Fish and Game Hatchery Manager for the Magic Valley area. Since brook trout was first introduced to the West in the early 1900s to expand fishing opportunities, he has said he has taken over high mountain lakes in the center and l east Idaho, particularly in the Big Lost area near Mackay.
The fish are so abundant that they threaten native populations of cutthroat trout and bull trout. And although they can grow to over 20 inches in captivity, Anderson said, overpopulation limits them to much smaller sizes in the wild. The stunting effect makes them unattractive to fishermen, Anderson noted.
âIt’s an introduced and prolific species from the east coast that has done better than it should,â Anderson said. “What is happening is that they are going to overpopulate and cut out what is supposed to be in our waterways – cutthroat trout, bull trout and rainbow trout.”
In the early 2010s, biologists from the Idaho Department of Fisheries and Game began to think about solutions to eradicate non-native fish. Some possible solutions were the introduction of musk or tiger trout in alpine lakes, chemical treatment of the lakes to kill any fish present, or the enlistment of fishermen to catch and slaughter brook trout one by one. But neither of these methods was effective or cost effective. So in 2013, the ministry established its YY male brook trout research program to reduce the population in a more sustainable and less invasive way.
The goal is simple: to distort the male / female ratio by intentionally creating âsuper maleâ trout which can only produce male offspring. Super males have two Y chromosomes instead of the usual XY arrangement and are created by selective breeding, Anderson explained.
The hope is that eventually the unwanted fish population – infiltrated by YY males – will produce fewer and fewer females and die.
Since 2015, when technicians at the Hayspur Hatchery started raising YY brook trout, the project has thrilled fish biologists and fisheries managers around the world, Anderson said. If proven effective, the methodology could be used to target problematic non-native fish populations in the eastern United States, such as Asian carp that have infiltrated the Mississippi River and surrounding waters.
Located south of Bellevue in Blaine County, the Hayspur State Fish Hatchery was established in 1907 and began breeding trout in the early 1920s. Today the facility produces 6-7 million trout per year.
The campus is large, with an incubation building for trout eggs, a hatchery building with breeding tanks, an office building, steel silos and 10 concrete raceways or canals.
On a special Tuesday in October, the hatchery technicians collect the pellets from a large 5-gallon bucket and distribute them to one of the facility’s rainbow trout runs, covered with wire. steel to keep herons, pelicans and piscivorous mink out. (Regulations are strict and all waters must be disease free. If a feral cat enters one of the raceways, for example, all fish in the channel must be culled.)
Nearby, brook trout are housed in large tanks and circular ponds surrounded by steel silos, one for each age group: first year, second year, third year and fourth year.
In one of the many closed silos, a batch of young brook trout is exposed to low doses of estradiol, a female sex hormone. While females are unaffected by estradiol, the hormone causes males in the group to mostly go through female puberty and produce eggs. The ovulating males are then mated with standard XY males, producing YY âsuper malesâ about 25% of the time.
The new generation of trout super-males – indistinguishable from XY males – continue to exclusively produce male fish when raised with any other brook trout. In the hatchery, the breeding process is speeded up by collecting milt and eggs on Tuesday and fertilizing the eggs in large plastic bags.
All standard XY males that hatch at Hayspur are chemically slaughtered, while YYs are either kept as broodstock or released into the wild to mate with wild females and amplify the wild male population.
At the age of four, YY brook trout weigh up to 2 pounds each and are slaughtered due to size constraints. (In the wild, brook trout have a rather short lifespan, on average about three years.)
Currently, 3-inch “fry” and 10-inch YY brook trout are being released into the wild by helicopter from high mountain lakes near Cape Horn Mountain north of Stanley to Spencer, according to Jared Riemenschneider, deputy director of the hatchery.
âAll of the indications that we have seen so far are very good,â said Anderson. âThis is a unique program in the world. ??