lake temagami fall walleye index netting project 2001
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Lake Temagami Fall Walleye Index Netting Project 2001. George Morgan Extension Biologist Cooperative Freshwater Ecology Unit. What is Index Netting?. - PowerPoint PPT PresentationTRANSCRIPT
George MorganGeorge Morgan
Extension BiologistExtension Biologist
Cooperative Freshwater Ecology UnitCooperative Freshwater Ecology Unit
Lake TemagamiLake TemagamiFall Walleye Index Netting Project 2001Fall Walleye Index Netting Project 2001
Index netting is a standardized, rapid Index netting is a standardized, rapid assessment technique or method that is assessment technique or method that is designed to determine relative abundance designed to determine relative abundance and provide other biological measures or and provide other biological measures or indicators of a fish population’s statusindicators of a fish population’s status
What is Index Netting?What is Index Netting?
Q&A: What method should I use to Q&A: What method should I use to assess my walleye population?assess my walleye population?
Are you interested in…Are you interested in… Adult and juvenile walleyeAdult and juvenile walleye
Is lethal sampling acceptable?Is lethal sampling acceptable? YesYes NoNo
Then use…Then use… Fall Walleye Index Netting (FWIN)Fall Walleye Index Netting (FWIN) Early Summer Trap Netting (ESTN)Early Summer Trap Netting (ESTN)
What is Fall Walleye Index What is Fall Walleye Index Netting?Netting?
Gillnetting procedure in the fallGillnetting procedure in the fall Net is 8 panels each 7.6m by 1.8m:Net is 8 panels each 7.6m by 1.8m:
– 25, 38, 51, 64, 76, 102, 127 & 152mm mesh25, 38, 51, 64, 76, 102, 127 & 152mm mesh
Temperature 15Temperature 151010ooCC Random net locationsRandom net locations 2 depth strata:2 depth strata:
– 2-5m & 5-15m2-5m & 5-15m
Kills fish!Kills fish!
What can you measure with What can you measure with FWIN?FWIN?
Species and number caughtSpecies and number caught Fork and total length, girthFork and total length, girth Wet, dressed, and filet weightWet, dressed, and filet weight Bony structures for age interpretationBony structures for age interpretation Determine sex and maturityDetermine sex and maturity Stomach contentsStomach contents Gonad weightGonad weight Organ weight (e.g., liver)Organ weight (e.g., liver) Visceral fat weightVisceral fat weight Contaminant and genetic samplesContaminant and genetic samples
Q&A: What method should I use to Q&A: What method should I use to assess my walleye population?assess my walleye population?
Are you interested in…Are you interested in… Adult walleye (>300mm total length)Adult walleye (>300mm total length)
Is lethal sampling acceptable?Is lethal sampling acceptable? YesYes NoNo
Then use…Then use… Fall Walleye Index Netting (FWIN)Fall Walleye Index Netting (FWIN) Early Summer Trap Netting (ESTN)Early Summer Trap Netting (ESTN)
What is Early Summer Trap What is Early Summer Trap Netting?Netting? Trapnetting procedure in the early Trapnetting procedure in the early
summersummer NSCIN net:NSCIN net:
– 1.8m trapnet with 45.7m leader1.8m trapnet with 45.7m leader
Temperature 12Temperature 121818ooCC Random net locationsRandom net locations Specific site selection criteriaSpecific site selection criteria Live release of fish!Live release of fish!
Species and number caughtSpecies and number caught Fork and total length, girthFork and total length, girth Wet, Wet, dressed, and filet weight?dressed, and filet weight? Bony structures Bony structures (spines)(spines) Determine sex and maturityDetermine sex and maturity Stomach contentsStomach contents Gonad weightGonad weight Organ weight (e.g., liver)Organ weight (e.g., liver) Visceral fat weightVisceral fat weight Contaminant and Contaminant and genetic samplesgenetic samples
What can you measure with What can you measure with ESTN?ESTN?
Lake Temagami isLake Temagami isNot your Typical Walleye LakeNot your Typical Walleye Lake
Lake TemagamiLake Temagami Area = 20971.7haArea = 20971.7ha Max. depth = 110mMax. depth = 110m Mean depth = 18.2mMean depth = 18.2m Secchi = 10.7mSecchi = 10.7m GDD = 1538GDD = 1538
Ontario Walleye LakesOntario Walleye Lakes Area 102 to 759haArea 102 to 759ha Max. depth 8.2 to 23.6mMax. depth 8.2 to 23.6m Mean depth 2.7 to 4.3mMean depth 2.7 to 4.3m Secchi 2.0 to 3.7mSecchi 2.0 to 3.7m GDD 1275 to 1500GDD 1275 to 1500
So… Lake Temagami is a large, deep, clear, cool lake (should be more favourable for coldwater species like lake trout).
Lake Temagami FWIN 2001Lake Temagami FWIN 2001
Concentrated sampling Concentrated sampling effort in “The Hub” effort in “The Hub” (recommended (recommended sampling area by Chuck sampling area by Chuck McCrudden)McCrudden)
Crew set and lifted 6 Crew set and lifted 6 nets per day from nets per day from September 26 to 30thSeptember 26 to 30th
Total of 24 sets (22 Total of 24 sets (22 useful sets; 2 tampered)useful sets; 2 tampered)
Lake Temagami FWIN 2001Lake Temagami FWIN 2001
WHAT DID WE CATCH?WHAT DID WE CATCH? 1 Lake trout1 Lake trout 49 Lake whitefish49 Lake whitefish 63 Lake herring63 Lake herring 8 Northern pike8 Northern pike 68 White sucker68 White sucker 1 Lake chub1 Lake chub
1 Burbot (Ling)1 Burbot (Ling) 105 Rock bass105 Rock bass 1 Pumpkinseed1 Pumpkinseed 38 Smallmouth bass38 Smallmouth bass 14 Yellow perch14 Yellow perch 127 WALLEYE127 WALLEYE
Making a DiagnosisMaking a Diagnosis
Compare observed FWIN walleye abundance Compare observed FWIN walleye abundance (number per net) to other Ontario lakes(number per net) to other Ontario lakes– Abundance compared to provincial and northeast region Abundance compared to provincial and northeast region
benchmarksbenchmarks
How is the healthHow is the healthof the “patient” today?of the “patient” today?
Walleye Relative AbundanceWalleye Relative Abundance
0
5
10
15
20
25
30
35
40
45
Temagami NE Benchmark Provincial Benchmark
Num
ber
of w
alle
ye p
er n
et
High
Average
Low
Lake Temagami abundance as expected based on climate and productivity.
Making a Diagnosis (Forecast)Making a Diagnosis (Forecast)
Compare biological parameters to regional Compare biological parameters to regional benchmarksbenchmarks
Compare biological parameters to regional Compare biological parameters to regional regression modelsregression models
Making a Diagnosis (Forecast)Making a Diagnosis (Forecast)
Compare biological parameters to regional Compare biological parameters to regional benchmarksbenchmarks
Compare biological parameters to regional Compare biological parameters to regional regression modelsregression models
What information can I get from a What information can I get from a FWIN survey?FWIN survey?
Relative abundanceRelative abundance Size distributionSize distribution Age distribution & mortalityAge distribution & mortality Growth & conditionGrowth & condition Sex ratio & maturitySex ratio & maturity Reproductive characteristicsReproductive characteristics Relative stock densityRelative stock density
ProtectedSlot
0
5
10
15
20
25
30
35
140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 740 780
Total Length (mm)
Perc
ent o
f th
e C
atch
Lake Temagami WalleyeLake Temagami WalleyeSize DistributionSize Distribution
Lake Temagami average size 362mm (14.2in). Smallest fish 132mm (5.2in). Largest fish 760mm (29.9in).
ProtectedSlot
0
5
10
15
20
25
30
35
140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 740 780
Total Length (mm)
Perc
ent o
f th
e C
atch
Corrected
Observed
Lake Temagami WalleyeLake Temagami Walleye“Corrected” “Corrected” Size DistributionSize Distribution
Lake Temagami slot will protect 5.7% of the population.
Lake Temagami WalleyeLake Temagami WalleyeAge Distribution (by sex)Age Distribution (by sex)
0
10
20
30
40
50
60
70
80
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Age (years)
Num
ber
of W
alle
ye
MalesFemalesUnknowns
Average age 2.5 years. Oldest fish 14 years. Balanced sex ratio (49% males: 51% females).
Lake Temagami WalleyeLake Temagami Walleye“Corrected” Age Distribution“Corrected” Age Distribution
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8
Age (years)
% o
f P
opul
atio
n
Corrected
Observed
Population supported by 3 strong year-class (1999 to 2001). Annual adult mortality is 29% after age 5 (too high).
ProtectedSlot
200
250
300
350
400
450
500
550
600
650
700
750
1 2 3 4 5 6 7 8 9 10
Age (years)
Ave
rag
e T
ota
l L
eng
th (
mm
)
NE male benchmark
NE female benchmark
Temagami males
Temagami females
Lake Temagami Walleye Lake Temagami Walleye GrowthGrowth
Lake Temagami male and female size is much higher than regional average after age 1.
Lake Temagami Walleye Lake Temagami Walleye ConditionCondition
200
400
600
800
1000
1200
1400
1600
1800
300 340 380 420 460 500 540
Total Length (mm)
Wei
ght (
g)
NE male benchmark
NE female benchmark
Temagami malesTemagami females
Lake Temagami male and female condition is higher than regional average.
ProtectedSlot
0
25
50
75
100
180 220 260 300 340 380 420 460 500 540 580 620 660
Total Length (mm)
Perc
ent M
atur
e
Temagami males
Temagami females
Lake Temagami Walleye Lake Temagami Walleye Maturity Maturity by Sizeby Size
Males 50% mature at 373mm (14.7in). Females 50% mature 448mm (17.6in) and 90% mature at 471mm (18.5in).
Lake Temagami Walleye Lake Temagami Walleye Maturity Maturity by Ageby Age
0
25
50
75
100
0 1 2 3 4 5 6 7 8 9 10
Age (years)
Per
cent
Mat
ure
Temagami males
Temagami females
Males 50% mature at 2.5yrs. Females 50% mature at 3.6yrs.
Lake Temagami WalleyeLake Temagami WalleyeEgg ProductionEgg Production
35000
40000
45000
50000
55000
60000
Temagami NE benchmark
Egg
s pe
r ki
logr
am
Lake Temagami egg production is much lower than regional average.
Lake Temagami Walleye Lake Temagami Walleye Fecundity-by-SizeFecundity-by-Size
0
50000
100000
150000
200000
250000
300000
380 420 460 500 540 580 620 660 700 740 780 820 860Total Length (mm)
Num
ber
of E
ggs
Temagami
NE benchmark
Temagami trendline
Lake Temagami fecundity is much lower than regional trendline.
Making a Diagnosis (Forecast)Making a Diagnosis (Forecast)
Compare biological parameters to regional Compare biological parameters to regional benchmarksbenchmarks
Compare biological parameters to regional Compare biological parameters to regional regression modelsregression models
Important life history questionsImportant life history questions
Tot
al L
engt
h (m
m)
Age at time t (yr)
L
Tmature
slop
e =
h
Lm
How fast do walleye grow?How fast do walleye grow? Pre-maturation growth is linearPre-maturation growth is linear Growth after maturity follows von Growth after maturity follows von
Bertalannfy growth formulaBertalannfy growth formula
When do walleye mature?When do walleye mature? What is their potential rate of What is their potential rate of
population increase?population increase?rr’’ = ( = (lnln fecundity @ L fecundity @ Lmm)/T)/Tmaturemature
Lt = L (1-e -K(t-t0 ))
Environment(Growing Degree Days, Secchi )
Early growth (h = mm/yr)h = 60.055 + 12.253 Secchi , R2 = 0.26
Relative ConditionRelative Conditionf = 0.762 + 0.0002 GDD , R2 = 0.24
Length at maturation (mm)Lmf = 369.116 + 0.782 h , R2 = 0.17
Potential population increase (r')r' = 0.020 h + 0.002 GDD - 1.477, R2 = 0.67
Asymptotic length (mm)L = 526.636 - 4.922 A% + 0.840 Lmf , R
2 = 0.60
Gonadosomatic index (%)GSIf = 1.725 + 0.024 h , R2 = 0.26
Visceral fat index (%)VFIf = -10.407 + 12.291 Conditionf , R
2 = 0.42
NE Female Walleye Life History Relationships
Lake Temagami Environmental Conditions(Growing Degree Days = 1538, Secchi = 10.7m?)
Early growth (h = mm/yr)Predicted h = 191mm/yr Observed h = 113mm/yr [Unexploited population h = 51mm/yr]
Relative ConditionPredicted Relative Conditionf = 1.07 Observed Relative Conditionf = 1.06
Length at maturation (mm)Predicted Lmf = 457mm Observed Lmf = 448mm
Potential population increase (r')Predicted r' = 3.85 Observed r' = 2.83 to 3.03
Asymptotic length (mm)Predicted L = 775mm Observed L = 792mm
Gonadosomatic index (%)Predicted GSIf = 4.43% NO DATA COLLECTED
Visceral fat index (%)Predicted VFIf = 2.62% NO DATA COLLECTED
Lake Temagami Female Walleye
Lake Temagami Walleye StatusLake Temagami Walleye Status
This lake supports a stressed This lake supports a stressed walleye population. The walleye population. The population is dominated by population is dominated by young, immature, fast growing young, immature, fast growing year-classes. Mortality is high year-classes. Mortality is high enough to lower the number of enough to lower the number of adult walleye present in this adult walleye present in this population and few fish reach population and few fish reach old age.old age.
Any Questions or Comments?Any Questions or Comments?