Download What do lake trout eat? - Yukon Fish and Wildlife Management Board

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Yukon Freshwater Fisheries
Presentation to YFWMB
April 2014
Nathan Millar
Senior Fisheries Biologist
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You asked
• 5.2 The Board further recommends the
Department of Environment… determine what
can be done to enhance populations over the
long term;
• The Board has also requested a scientific
presentation from the Department pertaining
to the effects of harvesting fish species such
as whitefish and burbot on the survival rates
of young lake trout and lake trout eggs.
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Today
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Impact of fishing: trends
Status of populations
What do anglers want?
Options
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Impact of fishing
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We encourage angling & stewardship ( )
Number of anglers is steady ( )
Amount of fishing is steady ( )
Fewer fish are harvested ( )
Technology has changed – boats, gear ( )
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Status of populations
How many?
• 45,000 lakes >1 ha. (9,000 km2)
• 8,000 lakes >10 ha.
• 850 lakes > 100 ha. (e.g., Coal, Lacelle)
• 75 lakes > 100 ha. (e.g., Squanga)
• 10 lakes > 1000 ha. (e.g, Frances)
We have surveyed 115. We focus on the ones
that get heavily fished and visit them repeatedly.
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Distribution of Angling
Effort in Yukon
Hours
Hours / ha
Fishing effort / impact is not
distributed equally across Yukon
•Centred in Southern Lakes
•Effort determined by access
33 fisheries where we have monitored harvest
Lake/Fishery
Jackson
Twin (West) Lake
Tarfu Lake
Snafu Lake
Caribou Lake
Frenchman Lake
Fox Lake
Pine Lake
Watson Lake
Fish Lake
Tatchun Lake
Little Atlin Lake
Kathleen Lake
Braeburn Lake
Ethel Lake
Laberge Lake
Marsh Lake
Lake Size
(ha)
65
160
405
651
32
1441
1660
548
1320
1320
654
4033
3376
558
4610
20100
9630
Year
2011
2013
2010
2010
1996
2012
2013
2009
2002
2010
2005
2008
2004
2001
2012
2007
2007
Estimated
Hours
Hours/ha.
757
11.65
1543
9.64
3141
7.76
3783
5.81
115
3.61
4564
3.17
5009
3.02
1185
2.16
2543
1.93
2376
1.80
750
1.15
4175
1.04
2265
0.67
299
0.54
2271
0.49
6706
0.33
3174
0.33
Lake/Fishery
Kusawa Lake
Simpson Lake
Dezadeash Lake
Quiet Lake
Tagish Lake
Teslin Lake
Aishihik Lake
Frances Lake
Bennett Lake
Kluane Lake
Tagish Bridge
Johnson's Crossing - Spring
Kathleen River
Lubbock River - Spring
McIntyre Creek
Nares River
Lake Size
(ha)
14200
2030
8250
5441
35460
35400
14500
9941
9680
39275
Year
2006
2002
2013
2011
2003
2008
2006
2009
2009
2004
2007
2001
2004
2010
2004
2009
Estimated
Hours Hours/ha.
4325
0.30
608
0.30
2429
0.29
1204
0.22
6888
0.19
6812
0.19
2456
0.17
1592
0.16
1020
0.11
2024
0.05
2420
322
3757
454
3190
2041
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Status of lake trout
500 – 1000 lakes that contain lake trout
Population assessments done on 115
Angler harvest surveys on 35
Most heavily fished populations
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Harvest is increasingly unsustainable
Harvest is sustainable
Summary: status of populations
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> 1,000 lakes with fishable populations
115 have been surveyed
Most activity takes place on 30 – 60 (?) waters
We know the harvest at 33
In most cases: the harvest is sustainable
Where harvest is unsustainable: we work with
RRCs, you, and anglers to develop and
implement solutions
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What do anglers want?
When you go angling, what is important to you?
What do you think are the most important
things to Yukoner anglers, as a whole?
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Ranking of Responses
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10
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Beauty of surroundings
Quality of water
Escape routine
Access to wilderness
Privacy (from other anglers)
Weather conditions
Angling for wild fish
Number of fish caught
Catch desired species
Rec. Fish Survey
1985
Size of fish caught
Catch as a source of food
What most contributes to your enjoyment of
sport fishing in Yukon?
1 Environment
2 Fish related
3 Fishing environment
4 Getting there
5 Socio-cultural
6 sport
beauty, water quality, wilderness
size, number, etc.)
not crowded
cost, ease of access
enjoyment, family, relax
challenge, excitement
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Ranking of Responses
0
Lack of Pollutants in Fish
Water Quality
Lack of Angler Crowding
Natural Beauty of the Area
Absence of Other Recreationists
Places to Fish From Shore
Presence of Wildlife
Presence of Favourite Species
Size of Fish
Information About the Area
Variety of Species Available
Catch Rate of All Fish
Cost
Distance/Travel Time
Catch Rate of Fish You Can…
Parking Availability
Chance to Catch a Trophy Fish
Boat Launching/Marina
Tourist Facility Quality
Nearness to Food/Lodging
Access to Other Recreational…
Nearness to Bait/Tackle Shops
Availability of Handicapped…
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Factors that play a role in
determining where to fish
Rec. Fish Survey
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1990 and 1995
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Ranking of Responses
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To Enjoy Nature
For Relaxation
To Get Away
Challenge and Excitement
Family Togetherness
To Catch Fish to Eat
For Companionship
Improve Your Skills
For A Sense of Achievement
To Catch a Trophy Fish
Why anglers fish
Rec. Fish Survey
1990 and 1995
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Ranking of Responses
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30
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Uncrowded sites
Lots of fish
Ease of access
Remoteness
Large fish
What is most important to
your angling experience
Rec. Fish Survey
2010
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Summary: what anglers want
• The natural environment, the fishing environment, sociocultural aspects are the most important
• Fish-related characteristics, logistics, and sport are less
important to most anglers
• When it does comes to the fish:
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Wild fish (1)
Number of fish caught (2, 1)
The ‘right’ species (3, 1)
Size of fish / large / trophy (4, 2, 2, 2)
Catch a fish to eat (5, 1)
Variety (3)
Catch rate (4)
• The “Average” Angler doesn’t exist
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Yukon Angler Psychographics
The Nature Seeker
-wants to get outside
-some are good anglers, some aren’t
-seeks appropriate setting
The Family Experience Seeker
-fishes as part of an outing or
activity to get the family
together
-practices live release and keeps
some fish
-amenities often important
-some are campground users
The Experience/Sport Seeker
-wants to catch a lot of fish
-practices live release
-typically an experienced angler
The Dinner Seeker
-wants to catch a fish to eat
-doesn’t practice live release unless required
-high frequency
-fish close to home where possible
The Holiday Seeker
-fishes as part of an outing or
other activity
-some are campground users
The Trophy Seeker
-wants to catch large fish
-typically an experienced angler
-possible gear intensive
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Questions
Given that anglers want different experiences
when fishing, what kind of a fishery (or fisheries)
best meets these interests?
Are some of these interests conflicting?
What makes fishing in Yukon different from
fishing elsewhere?
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What can we do?
Wild Populations
Enhanced Populations
Proactive regulations
Yes
Yes
Responsive Regulations
Yes
Yes
Stock Restoration
Yes
Stock Enhancement
Yes
Physical Habitat
Restoration /
Enhancement
Yes
Yes
Chemical Habitat
Restoration /
Enhancement
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Yes
Manipulation of Other
Species
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Yes
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Question
Do you place a different value on a fish caught in
a stocked lake and a wild caught fish?
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Definitions
Restoration
Returning a population (or habitat) to a natural level
Enhancement
Moving a population (or habitat) beyond a natural
level
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Lake productivity
• Primary productivity
– Production of organic matter
– Primary – at the base
• All about energy flows
• Root of all productivity: sun
– Photosynthesis
What are some of the environmental
constraints to fish production that exist here?
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http://www.sage.wisc.edu/atlas/maps/npp/atl_npp.jpg
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Productivity in lakes
• Temperature
• Sunlight
– Effect of ice
• Nutrients – phosphorus
and nitrogen
• Geology
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Experimental Lakes Area
Lake 226
Phosphorus
Eutrophication
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http://www.experimentallakesarea.ca/images/Eutrophication.pdf
Productivity across the landscape
Productivity is low
Limited by phosphorus and nitrogen
Oligotrophic and mesotrophic
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Fish Habitat
Installed correctly
Flood scours
pool
Mike Sullivan
Fish Passage &
habitat fragmentation:
culverts
Repeated floods
= barrier
Very expensive
to fix
Fragmentation
95% of
watershed
lost
2 species above
8 species below
Ñ
ò
Baseline Creek
watershed
Athabasca River, near Hinton
Craig Johnson (ACA)
Mike Sullivan
Question
If you harvest a species it will help (or hinder)
another species?
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Fish Ecology
• Competition
• Predation
Question:
What do lake trout eat?
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What lake trout eat in Yukon
Unidentified Fish
Non-Biting Midges
Caddisflies
Scuds, Sideswimmers
Unidentified
Invertebrates
Least Cisco
Pond Snails
Unknown
1000 stomachs
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lake trout
burbot
lake whitefish
Juvenile
lake
trout
lake chub
Caddisfly
(Tricopteran)
sculpin
round
whitefish
Midges
(Chironomids)
Copepod
(planktonic)
Gammarus
(Amphipods /
sideswimmer)
Water mites
Daphnia
Clams
Snails (gastropod)
Dragonfly
(Odonata)
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What lake whitefish eat in Yukon
Orb Snails
Copepods
Clams, Mussels
Non-Biting Midges
Snails
Scuds, Sideswimmers
Unknown
Pond Snails
Unidentified Invertebrates
Caddisflies
Leeches
Water Mites
Dragonflies, Damselflies
400 stomachs
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lake trout
burbot
lake whitefish
Juvenile
lake
trout
lake chub
Caddisfly
(Tricopteran)
sculpin
round
whitefish
Midges
(Chironomids)
Copepod
(planktonic)
Gammarus
(Amphipods /
sideswimmer)
Water mites
Daphnia
Clams
Snails (gastropod)
Dragonfly
(Odonata)
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Fish eat different things are different times
of their lives: ontogenetic shift
• Juvenile Lake Trout
– Eat benthos
– Suboptimal habitats
• Adult Lake Trout
– Eat fish
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1. Egg Predation
No literature confirmation
Eggs that don’t descend
have low survival anyway
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1. Juvenile Predation
The frying pan or the fire
3. Competition
lake trout
lake whitefish
Copepod
(planktonic)
Caddisfly
(Tricopteran)
sculpin
Midges
(Chironomids)
Daphnia
Clams
Gammarus
(Amphipods /
sideswimmer)
Snails (gastropod)
Dragonfly
(Odonata)
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Large bodied
Eat fish
Keep growing
Tend to be in larger lakes
Lakes haveNlake
whitefish
= 777
Small bodied
Eat invertebrates
Never get very big
Tend to be in smaller lakes
Lakes don’t have lake whitefish
Others
• Burbot – predatory and opportunistic
– Also a sport fish
• Round whitefish – opportunistic egg predators
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Summary
Many northern fish are generalist feeders
Caveats
Limitations on diet analysis – ‘point in time’, variation
between fish, some items more digestible.
Other techniques – stable isotopes of carbon and
nitrogen provide time averaged
Can you fish down predators and
competitors
• Species interact but not in simple ways
– Dietary overlaps (competition)
– Predation
– Interactions can be positive for juveniles and
negative for adults (for example)
• There may be tradeoffs between
– Species
– Size v. number
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References
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Lasenby, T.A., S.J. Kerr, and G.W. Hooper. 2001. Lake whitefish culture and stocking: an
annotated bibliography and literature review. Fish and Wildlife Branch, Ontario Ministry
of Natural Resources. Peterborough, ON.
Tolonen, A., J. Kjellman and J. Lappalainen. 1999. Diet overlap between burbot and
whitefish in a subarctic lake. Ann. Zool. Fennici 36: 205-214.
Beauchamp, D.A., M.W. Kershner, N.C. Overnman, J. Rhydderch, J. Lin, and L. Hauser.
2006. Trophic interactions of nonnative lake trout and lake whitefish in the flathead lake
food web. Reportted to the Confederated Salish-Kootenai Tribes.
Carl, L.M. 2008. Lake trout demographics in relation to burbot and coregonine
populations in Algonquin Highlands, Ontario. Envrionmental Biology of Fish 83: 127-138.
Fitzimons, J.D. 1996. The significant of man-made structures for lake trout spawning in
the Great Lakes: are they a viable alternative to natural reefs?. Canadian Journal of
Fisheries and Aquatic Sciences 53: 142-151 (Suppl).
Hulsman, M.F. 2012. Influence of fish competitors on lake trout trophic ecology in subarctic lakes. M.Sc. Thesis. University of Alberta.
Kerr, S.J. and T.A. Lasenby. 2001. Lake trout stocking in inland lakes: and annotated
bibliography and literature review. Ontario Ministry of Natural Resources.
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Stocking
• Restoration / Enhancement
• Divert Pressure
• Yukon
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Pothole lakes – no outflow
No stocking of open systems
Limited supply of pothole lakes
Previously fishless lakes
Have you noticed differences in fishing in a lake
that was stocked for the first time and that same
lake a decade later?
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20 Stocked Lakes
8% of all fishing
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Some issues with stocking open
systems
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Genetics – do you stock the same species?
Competition
Disease
Cost – initial, ongoing, monitoring
Unintended consequences
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A lake trout (mis)introduction
• Yellowstone Lake
• 1994 – Lake trout were
first found
– “bucket biology”
Native Cutthroat Trout
Solution – Lake trout suppression
Active netting
First 15 Years: 500,000 lake trout caught and eliminated
2011 and 2012: 525,000 lake trout caught and eliminated
2013: 172,000 in the first six weeks of the season
Netting out the lake trout
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