Blue Mesa Reservoir Fishery Management
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2012 Update on Blue Mesa Reservoir Activities
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Since
fish stocking began in Blue Mesa Reservoir in 1965, developing the
kokanee salmon fishery has been the major priority for Colorado Parks
and Wildlife. Unfortunately, the introduction of lake trout -- a
predator fish -- to the reservoir has taken a devastating toll on the
freshwater salmon population.
A decade ago, more than 1 million kokanee existed in the reservoir.
However, recent survey work by Colorado Parks and Wildlife biologists
show that the current population estimate is only about 280,000. That's a
slight increase from 2011, but far from the number of kokanee needed to
maintain a sustainable population.Fortunately, the salmon egg take in the fall of 2011 set a record: 11 million eggs from kokanee running out of Blue Mesa Reservoir. That amount ensures that it and 26 other reservoirs which rely on stocking will receive an ample supply of salmon fry next spring. The egg take eclipsed the previous mark of 9.2 million eggs harvested in 1993 and more than doubled the 5.4 million eggs taken in 2010.
Despite the good news, much more work needs to be done before agency biologists declare the population of kokanee salmon in the 9,000-acre reservoir recovered.
Management Improves Egg Take
"One good spawning run does not mean we've fixed the problems," said John Alves, senior aquatic biologist for Colorado Parks and Wildlife's southwest region. "Blue Mesa is critical for our statewide kokanee program and the fishery is out of balance. There is no quick fix."
While Blue Mesa's trophy lake trout often capture headlines, surveys show that more than 80 percent of the reservoir's anglers fish for kokanee, rainbow trout and brown trout.
Every year during fall, kokanee swim 20 miles up the Gunnison and East rivers to the Roaring Judy hatchery where they are spawned. As the state's largest kokanee fishery, Blue Mesa produces more eggs than any other reservoir and on average accounts for 60 percent of the overall egg take in the state.
Alves explained that egg collection is highly variable from year-to-year and from one body of water to another: "There are a multitude of factors that account for egg take; the high number does not mean we have a record number of kokanee."
Several factors contributed to the record egg production this year. Hatchery staff improved management techniques to assure that more fish make it into the hatchery where spawn is taken. These included: placing a net across the river near the outlet channel at the hatchery to keep fish from swimming past the hatchery; and preventing kokanee from moving out of the spawn-take facility once they've entered the channel.
To further help Blue Mesa's overall kokanee population, biologists have also increased the number of kokanee fry released into the reservoir by about 500,000 for each of the past three years. About 3.4 million fingerlings are released annually, with 3.1 million released into the East River and another 300,000 stocked by truck directly into the reservoir. Biologists have taken steps to make sure that the fingerlings released into the river make it to the reservoir. Screens are placed across irrigation ditches to prevent the small fish from entering those channels where they can't survive.
Kokanee, Lake Trout Harvest Improves
Maintaining
Maintaining an outstanding kokanee fishery is the top management
objective at the reservoir for Colorado Parks and Wildlife. Anglers
reported landing about 44,000 kokanee in 2011, more than double 2010's
take but significantly less than the 130,000 fish harvested in 2002. Providing angler opportunity for trophy lake trout is also a management goal. Biologists' fish surveys this year showed that the body condition of lake trout is continuing to improve. More of the fish are round and plump -- as they should be -- instead of long and thin. While lake trout are able to survive on little food they don't gain weight if they face too much competition for food.
"Lake trout anglers don't want to catch skinny fish," Alves said. "Without kokanee, trophy lake trout opportunities will decline. We must maintain a biological balance in the reservoir, increase the number of kokanee and provide opportunities for the greatest number of anglers."
Angler harvest of lake trout is another key to restoring balance to the fishery. Colorado Parks and Wildlife has encouraged harvest of lake trout during the last few years and anglers appear to be taking up the challenge. This year anglers harvested a record 5,670 lake trout, up from 3,849 in 2010 and more than the previous record of 4,664 in 2007. "We really appreciate that anglers are stepping up," he said. "Angler harvest can really help us to maintain a balanced fishery."
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Balancing the Fishery at Blue Mesa Reservoir
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Blue Mesa Reservoir is one of the most productive fisheries in Colorado. The water is pristine and the reservoir is the largest in the state at 9,000 surface acres. The No. 1 fishery management priority is kokanee salmon.
At
an elevation of 7,520 feet, the water in Blue Mesa warms up enough to
produce large quantities of zooplankton, which in turn, provide the
primary food source for kokanee. The connection of the reservoir to the
Gunnison River also provides a unique environment for kokanee to run
upstream to spawn at the Roaring Judy Hatchery, where the DOW can
collect salmon eggs every fall. Blue Mesa is the primary source for
kokanee eggs used for producing salmon for more than 20 reservoirs
throughout Colorado.The reservoir also provides ideal conditions for lake trout and natural reproduction has increased steadily during the last decade. The reservoir is deep --330 feet at the deepest-- so there is plenty of room for the lake trout to descend to cold water during the summer. Shallow areas along the banks are relatively flat in some areas, providing ideal fall spawning beds. Lake trout are predators, and live primarily by eating kokanee salmon and rainbow trout.
A
critical factor in understanding the Blue Mesa fishery is that the
reservoir is a human-made impoundment. The biology of a reservoir is far
different than a natural lake, and managing a fishery in this type of
environment is challenging. The fish are not native to the environment
and the species did not evolve together. Consequently, the predator-prey
relationship is not natural. In Colorado reservoirs some fish can
reproduce naturally, others must be stocked, and some species
(specifically yellow perch at Blue Mesa) have been introduced illegally.Balancing the fishery at Blue Mesa Reservoir for the benefit of resident and non-resident anglers is the goal of the Colorado Division of Wildlife. The reservoir is managed first and foremost for kokanee salmon. Blue Mesa is also managed for rainbow and brown trout, and lake trout.
Removing Lake Trout
In many wildlife environments a predator-prey relationship exists; but a balance between the species must be maintained to ensure the survival of both. At Blue Mesa Reservoir, lake trout are consuming significant numbers of kokanee and the predator-prey relationship is dangerously out of balance. Lake trout are also adversely impacting the stocked supply of rainbow trout.
To restore the balance to the fishery in the reservoir, targeted removal of lake trout is part of the fisheries management plan of Colorado Parks and Wildlife. Parks and Wildlife biologists will continue to assess the effects of the removal effort on kokanee and lake trout populations and make management adjustments as needed.
As lake trout grow in size their consumptive demand for prey increases. Fish that are 17 to 30 inches in length can consume 13 pounds or more of kokanee salmon annually. A 40-inch lake trout can eat 50 pounds or more. The removal operations have targeted primarily fish that are 30 inches or smaller, although some fish up to 38 inches are removed.
In 2011, 1,333 lake trout were removed, with 1,298 of those--97 percent--under 30 inches in length. A total of 35 fish that measured from 30 to 38 inches were removed. Five fish that measured more than 38 inches were released back to the reservoir. This level of removal, along with continuing angler harvest, hopefully, will accomplish the objectives of reducing the lake trout population and halting overall population growth.
Biologists from Colorado Parks and Wildlife and Colorado State University are studying survey and catch data to determine future strategies. Close evaluation of the removal program is ongoing.
By removing fish, the predation on kokanee will decline and trophy-sized lake trout that remain will face less competition for their primary food source. Anglers targeting trophy lake trout are primarily searching for fish weighing 25 pounds or more. Fish of that size can only be sustained by assuring that adequate numbers of kokanee exist. At lakes and reservoirs throughout the West, no other prey species has been able to replace kokanee as the forage fish for sustaining trophy lake trout.
Numerous Western States Face the Same Issue
Lake trout predation on kokanee salmon is not a problem exclusive to Colorado. Wildlife agencies in Wyoming, Idaho, Montana, California, Utah and Washington are also working to maintain their kokanee populations.
You can learn about how this issue is affecting all of these western states by reading Introduced Species: Western Lake Trout Woes , published in "Fisheries," the journal of the American Fisheries Society. The paper explains the extensive research on the kokanee-lake trout issue and possible solutions. Economic Impact of Kokanee at Blue Mesa Reservoir
All types of fishing at Blue Mesa Reservoir are important to the economy of Gunnison County. But based on years of surveys, kokanee anglers are the most active at the reservoir. In 2004, a study estimated that fishing at Blue Mesa generated an economic impact of about $8 million per year. Of that amount, 80 percent of the spending -- about $6.4 million -- came from kokanee anglers. Kokanee fishing is popular and people from throughout Colorado and the United States travel to Blue Mesa to fish for them. But in the last few years, the number of kokanee anglers has declined substantially.
Beyond the immediate impacts in Gunnison County, kokanee production at the reservoir is critical to sport fishing throughout Colorado. Blue Mesa provides an average of 60 percent of the eggs needed to stock fingerlings in 26 other lakes and reservoirs in the state. The overall annual economic impact of kokanee salmon fishing in Colorado is estimated to be at least $29 million.
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Aquatic Sport Species in Blue Mesa Reservoir
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Kokanee SalmonKokanee
salmon were first stocked in Blue Mesa Reservoir in 1965. Even before
the reservoir was built, aquatic biologists recognized that it would be
an ideal environment for the fresh-water salmon. The water is very clean
and produces an abundance of zooplankton which is the primary food
sources for kokanee. Kokanee do not compete with native fish, they
cannot cross-breed with other spe-cies and they can be released as
fingerlings. They live in open wa-ter, so the large size of the
reservoir provides excellent habitat. Kokanee also grow to an ideal size
for anglers, 15-18 inches, and provide very tasty meat.
The location of the reservoir also allowed the CPW to build a
highly-efficient and cost-effective kokanee rearing facility at the
Roaring Judy hatchery. Eggs hatch in the facility in December, and the
young are raised to a length of 2 inches in the hatchery building. In
April, they are released directly into a one-half mile long canal which
flows into the East River/Gunnison River system. The finger-lings move
down the river 21 miles until they arrive at Blue Mesa Reservoir.After three to four years of living in the reservoir, the fish respond to their natural instincts and make their way back up river seeking the place where they were released. They swim into the fish race-ways just below the hatchery where their spawn is collected. Every year CPW is able to develop a new year-class of fish.
Rainbow troutRainbow trout are the most popular game fish in Colorado. The U.S. Fish and Wildlife Service annually stocks 120,000 catchable-size (10 inches) rainbows in Blue Mesa. The trout are raised at the federal hatchery in Hotchkiss. Before 2009, fingerling trout were stocked, but they were more vulnerable to lake trout than larger trout. But even the catchable-size trout are no match for lake trout and predation is significant. Some rainbow trout reproduce naturally in several Blue Mesa tributaries, but not in large enough num-bers needed to sustain a sport fishery in the reservoir.
Brown troutBrown trout reproduce naturally in the Gunnison River, the Lake Fork of the Gunnison River and Cebolla Creek. The fish then move into the reservoir as they get older. Their population has held steady and has not been impacted by lake trout. Browns are predators and do eat small kokanee; but their predation effect is insignificant compared with lake trout. Brown trout prefer water near the banks of the reservoir and water depths shallower than 65 feet.
In 2005, anglers caught about 9,800 brown trout that averaged 14.5 inches in length. In 2011, angler catch totaled about 10,000.
Lake trout
Lake
trout -- also known as Mackinaw -- are natives of northern North
America. This predator species is the largest trout on the con-tinent
and can routinely grow to 25 pounds or more if they have a reliable
source of other fish to eat. The largest lake trout taken at Blue Mesa,
caught in 2007, weighed 50 pounds. They were first in-troduced to Blue
Mesa in 1968. Subsequent stocking occurred in the early 1970s, 1980s and
1990s. Lake trout spend most time in open water, the same area favored
by kokanee.At the time the lake trout were introduced it was believed that they would not naturally reproduce in the reservoir. This proved true un-til the early 1990s when water management at Blue Mesa was changed which reduced water level fluctuation in the winter. Conse-quently, shallow areas remain under water throughout the winter, allowing spawn produced by lake trout in the fall to survive. Since then, the species has reproduced naturally, the population has grown significantly and lake trout have become the major predator fish in the reservoir.
Surveying Fish Populations
Determining
the exact number of fish in any body of water, especially in a
reservoir the size of Blue Mesa, is difficult. However, using a variety
of methods, aquatic biologists can learn a lot about the status of the
populations of various species. These methods have been tested, refined
and accepted by the scientific fisheries management community across the
United States.
Methods include: sonar technology to count open water fish; angler
surveys -- also known as creel surveys -- to estimate catch, harvest and
fishing pressure; live fish surveys using electro-fishing or net
sampling to study body condition, growth, diet and abundance; and by
tracking how many fish are stocked in a body of water each year.These methods have revealed that the kokanee population has dropped significantly during the last 10 years. In 2000, the CPW estimated the Blue Mesa kokanee population at about 1 million. Now, the population is estimated to be only about 290,000 -- despite the stocking of more fish whenever possible. That represents a decline of more than 70 percent.
While the catch of kokanee has dropped substantially, angler surveys show that the catch of lake trout has increased significantly -- an indication that the population is growing fast. In the late 1990s, summer creel surveys showed that anglers caught about 1,700 lake trout per year. In 2011, anglers harvested a record 5,700 lake trout.
The estimated kokanee catch in 2000 was 130,000. Kokanee catch did rebound in 2011 from 2010 lows, but catch of 44,500 was still significantly below previous levels. Creel surveys also show that lake trout predation is taking a large toll on rainbow trout. In 2005, anglers caught about 40,000 rainbows. In 2011, the estimated catch was only 13,100.
Perch, which were introduced illegally to Blue Mesa years ago, are also a prime target for lake trout. In 2005, anglers caught about 8,000 perch. In 2011, catch totaled 1,600. Surveys and creel counts have found that perch are abundant; however, they are of very small size -- most just six inches or less.
The fishery can be restored to a balance at Blue Mesa Reservoir through sound management practices. Anglers can also assist by keeping the lake trout that they catch. The more fish anglers keep the fewer the fish we must remove. The bag limit for lake trout smaller than 38 inches is unlimited. Anglers can keep one lake trout larger than 38 inches. By removing fish, anglers can help to slow the rate of population growth of lake trout and preserve trophy opportunities. Lake trout are tasty and provide healthy and nutritious food.
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