Blue Mesa Fisheries Update - Colorado Parks and Wildlife · Dan Brauch and Adam Hansen Colorado...
Transcript of Blue Mesa Fisheries Update - Colorado Parks and Wildlife · Dan Brauch and Adam Hansen Colorado...
Blue Mesa Fisheries Update
Dan Brauch and Adam HansenColorado Parks and Wildlife
December 18-19, 2019
Blue Mesa Fish UpdateBMR fisheryKokanee managementLake trout managementLake trout harvest incentive
Blue Mesa Fishery Goals
Goal #1: Provide Blue Mesa anglers with best fishing opportunities for kokanee, rainbow trout, trophy lake trout and brown trout.
Goal #2: Maintain Blue Mesa as source of kokanee eggs to provide kokanee fishing opportunities at 28 lakes in Colorado.
Blue Mesa Reservoir Fisheries
Supports up to 450,000 hours of angling annually.“Destination” Fishery—Up to 2/3 of anglers are from Colorado’s East Slope or from out of stateGross economic estimated to be $12.3 million in today’s dollars ($5.43 million in 1987).Curecanti NRA was responsible for an estimated $44 million in economic value in 2014.
Kokanee & lake trout are not co-evolvedLake trout stocked in Colorado in late 1800’s, Kokanee in 1951
Kokanee and Lake Trout
Blue Mesa Kokanee• Stocked after Blue Mesa Dam completed (1965)
with Granby source (Flathead L, MT 1951-1957)• Currently states primary egg source—natural
reproduction is minimal in Colorado
02468
1012141618
Egg
Tota
l in
Mill
ions
Year
Kokanee Spawntake Totals by Water 2000-2019
Antero
Blue Mesa
Cheesman
Eleven Mile
Granby /Shadow Mt.
McPhee
Lake Nighthorse
Vallecito
Williams Fork
Wolford
Kokanee Fishing
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Kokanee percent of total catch
Year
Kokanee Contribution to Blue Mesa Catch May through October
Kokanee Grow Trophy Trout
0%
20%
40%
60%
80%
100%
age 3 age 4-6 age 7-25
InvertebratesCrayfishPerchRainbow TroutKokanee
Stable Isotope proportion of MAC diet 2010 (CSU)
MAC Age
Die
t Pro
porti
on
(12-16”) (17-23”) (24-44”)
Sonar transects
2009
2002
Sonar Estimates 1994-2019
Lake Trout Management / Regulations
• Late 1980’s 1 fish over 20 inches (86-87)• 1990-1995 22-34 inch fish must be returned
(slot)• 1996-2010 8 fish bag limit• 2009- 2011 CPW netting to reduce predation
AND reduce reproductive capacity• 2011- 1 fish over 38 inches, unlimited under 38• 2012-2017 CPW netting to reduce predation
(reduced length target: 32” to 30” to 28”)• 2016- 1 fish over 32 inches, unlimited under 32
Lake Trout Abundance
Predatory Lake Trout Abundance
• Goal 1: Manage predation on kokanee to maintain kokanee fishing, eggtake and prey availability for trophy lake trout
• Goal 2: Provide quality opportunities for trophy lake trout
Lake Trout Management 2020
2 Tools: Angler harvest and CPW netting
0
50
100
150
200
250
300
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
Angler Returned 09-12 Angler Harvested 09-12
Angler Catch 2009-2012
0
500
1000
1500
2000
2500
3000
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
Netting Removal Incidental Mortality Netting Released
Netting Catch 2009-2019Incidental mortality a concern
Lake Trout Harvest 1996-2018
Netting Catch 2009-2019Not popularIncidental mortality a concern
Kokanee VS Lake Trout Abundance
• Only incentivize harvest up to 24 inches:• Consume the most kokanee• 96 percent of lake trout removed by CPW AND of
lake trout kept by anglers are 24 inches and smaller.
• 83 percent of released lake trout under 24 inches• Harvest about 30%, far below unsustainable levels,
so significantly more harvest can occur (>50%-55% continued harvest would likely be unsustainable)
• Population monitoring and modelling will guide program (creel, sonar, SPIN lake trout study) to insure moving towards goals.
Lake Trout Harvest Incentive Proposal
• Only heads accepted from fish under 24 inches• Dropped off at CPW offices (Gunnison and
Montrose) and Blue Mesa?• Propose 2020 contest February through July• Prizes for:
• Most lake trout turned in ($1000, $500, $250??)• Turned in coded wire tagged fish (propose $250
per tagged fish)• Randomly selected (one chance per head turned
in) 20 $200 prizes• Other donated prizes?
Lake Trout Harvest Incentive Proposal
• Continue stocking 3.5 million kokanee annually
Blue Mesa Recommendations
• Maintain kokanee survival by managing lake trout population/predation through angler harvest; achievable at Blue Mesa?
• Resume netting if angling harvest is shown to not control population growth; minimize netting
Blue Mesa Recommendations
• Assess lake trout management annually and provide recommendations for changes
• Maintain kokanee, brown trout, rainbow trout and trophy lake trout angling opportunities
• Monitor gill lice to assess effect on kokanee fishery
Blue Mesa Recommendations