Horsetooth Reservoir
Transcript of Horsetooth Reservoir
General Information: Horsetooth Reservoir (1900 acres) provides quality fishing for walleye, smallmouth
bass, and trout. Anglers may also catch white bass, crappie, bluegill, and perch. The lake is open year round
to fishing. For more information visit the park’s website: http://www.co.larimer.co.us/parks/Horsetooth.htm
Location: Larimer County. From I-25, go west on Harmony Road 7 mi. to where it becomes CR 38E at Taft
Hill Road. Continue west 4 more miles on CR 38E to park entrance.
Recreational Management: Larimer County
Fishery Management: Coldwater and coolwater angling
Purchase a Fishing License: http://cpw.state.co.us/buyapply/Pages/Fishing.aspx
Regulations
Walleye regulation: 5 fish
bag limit, no size restriction
Minimum size for small-
mouth is 12”
Statewide bag and posses-
sion limits apply for all
other species
Fishing prohibited in inlet
March 15 - May 31
Entry requires a Larimer
County Parks Pass available
on site
Horsetooth Reservoir
FISH SURVEY AND MANAGEMENT DATA Kurt Davies - Aquatic Biologist (Fort Collins)
[email protected] / 970-472-4396
Amenities
4 Boat Ramps
Swim Beach
Modern Restrooms
RV hook-ups
Tent Camping
Camper Cabins
Hiking Trails
Marina
Picnic Areas
Previous Stocking
2013
Rainbow Trout
Cutthroat Trout
2012
Rainbow Trout
Cuttbow
2011
Rainbow Trout
2010
Rainbow Trout
2009
Splake
Rainbow Trout
Cutthroat Trout
Cuttbow
Mercury Advisory
Some fish in Horsetooth have
been found to have significant
levels of mercury. A consump-
tion advisory is in effect. For
more information go to:
http://www.cdphe.state.co.us/
wq/FishCon/
HorsetoothADVISORY.pdf
Sportfishing Notes
Walleye
Fish rock structures when
water temps are 40-55°F.
Later, fish are scattered but
tube jigs, lindy rigs, triple
ripples, are good choices.
White Bass
Watch for surface activity
in the coves, small fish or
birds on the surface, that
indicate feeding fish below.
Smallmouth Bass
Try rock rip-rap areas with
crayfish imitations.
History Horsetooth Reservior was completed in 1949. It is part of
the Colorado-Big Thompson Project (CBT) transporting water from
the west slope and storing it for east slope use. Water operations are
conducted by the Bureau of Reclamation and the Northern Colorado
Water Conservancy District. Expect large water fluctuations in the
reservoir from seasonal water use.
Horsetooth has been managed for cool and coldwater assem-
blies of fish since the 1950’s. Various proportions of rainbows, cut-
throats, browns, mackinaw and splake have made up the coldwater
assembly over time. Coolwater fish like walleye, smallmouth bass,
white bass, and yellow perch have been stocked historically and now
maintain self-sustaining populations.
Horsetooth has had a very dynamic fishery. A large yellow
perch population provided a great forage for walleye from the filling
of the reservoir until the late 1960’s when the population crashed.
When walleye body condition and growth fell to unacceptable levels
as a result, rainbow smelt were introduced as an alternative forage.
This led to a boom in walleye fishing in the 1980’s and 90’s. The
smelt ended up eating themselves out of house and home, affecting
the recruitment of walleye and other fish. The smelt population sub-
sequently crashed and brought the whole reservoir ecosystem down
with it. Smelt disappeared in 1996 and were not seen again for over
a decade
Efforts in the last decade have been to reestablish a quality
forage base without the potentially detrimental effects that smelt had
on the fishery. Spottail shiners, emerald shiners and gizzard shad
have been successfully introduced and represent a significant com-
ponent of the fishery. Walleye maintain a self-sustaining population
and their body condition and growth have continued to be on the rise
for the last few years.
Smelt began to show up again in our sampling in 2010 and
in the last three years, the population has grown from undetectable to
an estimated 2.5 million in 2013. This has created a very dynamic
fishery that will see significant reservoir-wide changes for many
years. We will be monitoring this and making changes when possi-
ble to promote optimal smallmouth and walleye fisheries.
Horsetooth Reservoir
FISH SURVEY AND MANAGEMENT DATA
Kurt Davies - Aquatic Biologist (Fort Collins)
[email protected] / 970-472-4396
Management
Emergency Trout Salvage:
In 2012 a large number of trout were put into Horsetooth Reservoir from Watson Hatchery in response
to adverse conditions caused by fires in the Cache la Poudre watershed. While there were no significant ef-
fects on fish in the river, the poor water quality coming into the hatchery with fish at high densities led to
stressful conditions. To avoid a large kill, and the loss of these fish, they were evacuated to the nearest body
of water that could take the numbers. Approximately 72,750 trout weighing 23,100 pounds were moved in
one day to Horsetooth. Horsetooth is not typically stocked with rainbows because we get a very poor return to
anglers, but this emergency measure should lead to a large number of trout being caught over the next few
years. Enjoy it while it lasts.
Rainbow Smelt:
From our standardized sonar sample, the
smelt numbers were similar in both 2011 and
2012 with estimates around 1.5 million. Sam-
pling in 2013 showed a significant bump in the
population up to an estimated 2.5 million. This
suggests that while we have yet to see a massive
exponential rise in the population that we saw in
previous decades, the population may be on the
rise. The graph on the right shows the range of
smelt sizes sampled. The 2012 data is from the
spring and the 2013 from fall samples. Smelt
historically reached over 8 inches (200mm) but
we have yet to see many fish reaching those up-
per age classes.
Gizzard Shad:
Gizzard shad introduction in
Horsetooth appears to be increasing
in success. The population continues
to successfully reproduce and main-
tain a strong presence in the reser-
voir. This is very beneficial, adding
to the diversity of forage in the reser-
voir and helping to avoid a total sys-
tem crash if dependent on only one
forage species. Most of the 2013
samples were small young of the
year fish under one inch in length.
Horsetooth Reservoir
FISH SURVEY AND MANAGEMENT DATA
Kurt Davies - Aquatic Biologist (Fort Collins)
[email protected] / 970-472-4396
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Horsetooth Combined Sampling
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Length Bin (millimeters)
Horsetooth Rainbow Smelt Gillnet Samples
Length-Frequency 2012 and 2013
2012 2013
Management
Walleye:
Body condition of walleye in Horse-
tooth has been steadily increasing since 2010.
The first graph to the left shows body condi-
tion factor. An average, healthy walleye in
Colorado should have a relative weight (Wr)
of 96. There was a significant decline after
1995 when smelt crashed in the reservoir.
From a low of 79 in 2010, walleye Wr in 2013
has climbed to 91. The vertical bars show the
95% confidence interval for the data each
year, taking into account the number of fish
measured and the variation within the sample.
There seem to be two populations present in
the near-shore electrofishing sample that may
be making use of different forage items. One
still in poor condition, with an average Wr of
82, and one in fantastic condition with an av-
erage Wr of 130. This is why you see such a
large confidence bar and an average of the
electrofishing sample at 107.
In the second graph you can see the
difference that exists in the number of fish
captured by each gear. Walleye numbers still
remain high in 2013. This equaled about 24
walleye/net, which was higher than any other
Colorado lake sampled in 2012. The peak in
the 1990’s was at the height of the smelt
population and the peak in 2004 was immedi-
ately following the draw-down of the reser-
voir.
The last graph shows an average
length for all the walleye caught with each
gear. Each gear has a bias especially toward
smaller and young of the year fish. Only 2
fish from the electrofishing sample were over
12 inches, while 305 fish from gillnets were.
There was reproduction in 2012, but the
young of the year numbers were lower in the
electrofishing sample and offset by an untyp-
ical number of relatively large fish around 400
mm (16 inches).
Horsetooth Reservoir
FISH SURVEY AND MANAGEMENT DATA
Kurt Davies - Aquatic Biologist (Fort Collins)
[email protected] / 970-472-4396
Management
Walleye:
In addition to improving the condition and numbers of walleye in Horsetooth, the increasing forage
base in the reservoir seems to be allowing the walleye to overcome their previous stunted condition. In
2010, fish over 18” represented less than 0.5% of the population. In 2013 that number has grown to
over 7.5% and looks like it will continue to increase.
Horsetooth Reservoir
FISH SURVEY AND MANAGEMENT DATA
Kurt Davies - Aquatic Biologist (Fort Collins)
[email protected] / 970-472-4396
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Inches
Horsetooth Walleye Length-Frequency Gillnet
Sampling 2010-2013
2010 2011 2012 2013
Management
(Due to poor water conditions for the sampling effort, the 2011 data is shifted lower than typical)
Smallmouth Bass:
The average temperature in Horsetooth is colder than most comparable lakes in the area because the
water comes through the Colorado-Big Thompson Project pipeline from a very cold Grand Lake. This factor,
coupled with relatively low productivity, limits smallmouth growth to about 2 inches/year. This slow growth
rate makes Horsetooth a poor candidate for trophy smallmouth management. It takes about 6 years for a
smallmouth to reach harvestable size at the protected 12 inch minimum size limit in the reservoir. This limit
allows sufficient age and growth for successful reproduc-
tion. With this regulation, smallmouth bass have no re-
cruitment limitations in Horsetooth. It is unknown at this
point how much the smallmouth will take advantage of
the resurgence of rainbow smelt but the growth rate could
increase if they were able to do so. In recent creel sur-
veys, only 7.5% of all smallmouth caught were harvested,
half falling between 12 inches and 13 inches.
To the right, the representative species, relative com-
position, and length and weight ranges for both gill net
and electrofishing samples are shown. Keep in mind that
these numbers show the extremes of the fish that were
collected during sampling. Zeros on the weight range are
young fish weighing less than 0.1 pounds.
Horsetooth Reservoir
FISH SURVEY AND MANAGEMENT DATA
Kurt Davies - Aquatic Biologist (Fort Collins)
[email protected] / 970-472-4396