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Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

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Page 1: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Status of Lake Trout in the Main Basin of Lake Huron: A

Summary of (SCAA) Models and Projections

Aaron Woldt--MDNR Alpena

Page 2: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Background• Lake Huron lake trout stocks crashed due to

overfishing and mortality due to sea lamprey in the 1940’s

• Rehabilitation efforts started in the 1970’s and consisted primarily of:

» supplemental stocking» lamprey control» fishery regulation

• Lake trout stocks are monitored annually by MDNR, CORA, USGS BRD, OMNR, and USFWS

Page 3: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

We developed 2 types of models

1) SCAA model--uses user supplied inputs and iteratively solves for population parameters like M, F, Z, abundance, SSB….

2) Projection model--uses last year’s output from SCAA model to predict population parameters into the future (2020 in our case). Also allows user to alter projection parameters (i.e. effort).

We developed both model types for each modeled area

Page 4: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Inputs to SCAA model

• Stocking (w/ movement matrix)

• Commercial fishery effort and yield (state licensed, tribal, and Canadian) from LMGN, SMGN, and trap nets

• Recreational fishery effort and harvest

• Commercial and recreational harvest age compositions

• Mean weight of lake trout harvested by each gear (LMGN, SMGN, trap net)

Page 5: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Inputs to SCAA model (cont.)

• Estimate of under-reporting or discards• Survey catch, CPE, and age compositions• Estimate of natural mortality• Estimate of sea lamprey mortality rates at age by year• Estimate of trap net by-catch mortality• Estimate of lake trout weight at age• Estimate of lake trout maturity at age • Estimate of fecundity

Page 6: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Areas modeled using SCAA

NorthernNorth-centralSouthernNot modeled

Model Key

MH-1 and 4-1

MH-2, 4-2, 4-3, and 4-7

MH-3, MH-4, MH-5,4-4, and 4-5

Page 7: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Credit:GLFC

Is this natural?

Sources of Mortality

Page 8: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

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Historic lake trout spawning reefs

Page 9: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997

Year

Inst

anta

neou

s M

orta

lity

Rat

e (Z

) RecreationalCommercialLampreyNatural

Average instantaneous mortality rates for ages 3-13 lake trout in N. L. Huron

Page 10: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Nu

mb

er

of L

ake

Tro

ut

1994-98 average lake trout population age structure in N. L. Huron

1,818 523 163 1445 5 1 07,359

Page 11: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0

100

200

300

400

500

600

700

1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997

Year

Biom

ass

X 1,

000

kg

Total Biomass

SSB

SCAA model estimates of lake trout biomass and SSB in N. L. Huron

Page 12: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

N. L. Huron Projection Scenarios

0.000

0.050

0.100

0.150

0.200

0.250

Targe

t A =

0.4

5

Curre

nt (1

998)

Lam

prey

Only

Total F

-50%

Total F

-63%

Comm

-50%

Comm

-60%

Comm

-70%

Comm

-50%

+ 2

4"

Comm

-60%

+ 2

4"

Comm

-70%

+ 2

4"

SS

BR

Page 13: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1984 1986 1988 1990 1992 1994 1996 1998Year

Inst

anta

neou

s M

orta

lity R

ate

(Z)

RecreationalCommercialLampreyNatural

Average instantaneous mortality rates for ages 3-13 lake trout in N.C. L. Huron

Page 14: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

500,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Nu

mb

er

La

ke

Tro

ut

1994-98 average lake trout population age structure in N.C. L. Huron

4,6022,161

1,330 734 305 16521,648

11,2608,195

Page 15: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0100200300400500600700800900

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

Year

Biom

ass

X 1,

000

kg

Total Biomass

SSB

SCAA model estimates of lake trout biomass and SSB in N.C. L. Huron

Page 16: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

CPE of YOY lake trout at North Point Thunder Bay

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Year

CPE

(YO

Y/to

w)

Combination of habitat and adult spawners, albeit a low level of spawners

Page 17: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

N.C. L. Huron Projection Scenarios

0.000.100.200.300.400.500.600.700.800.901.00

SS

BR

Page 18: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0.000.050.100.150.200.250.300.350.400.450.50

1984 1986 1988 1990 1992 1994 1996 1998Year

Inst

anta

neou

s M

orta

lity

Rat

e (Z

)

RecreationalCommercialLampreyNatural

Average instantaneous mortality rates for ages 3-13 lake trout in S. L. Huron

Page 19: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

Nu

mb

er

La

ke

Tro

ut

1994-98 average lake trout population age structure in S. L. Huron

9,8966,331

4,322

2,5872,241 617

112,999

56,559

24,742 1,466927

Page 20: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

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Historic lake trout spawning reefs

Potential for natural production in MH-3,4,5??Relatively high numbers ofspawners (5X that of MH-2)but little nearshore habitat.

We currently do not trawlfor juveniles in MH-3,4,5

Page 21: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0

500

1,000

1,500

2,000

2,500

3,000

3,500

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

Year

Biom

ass

X 1,

000

kg

Total Biomass

SSB

SCAA model estimates of lake trout biomass and SSB in S. L. Huron

Page 22: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Estimated lake trout sport catch, Michigan waters of Lake Huron

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

1986 1988 1990 1992 1994 1996 1998

Year

Num

ber o

f fis

h

MH-6MH-5MH-4MH-3MH-2MH-1

**note 1999 catch does not include charter boats

Page 23: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Targ

et A

= 0

.4

Curre

nt (1

998)

Lam

prey

Onl

y

Tota

l F -5

0%

Comm

-50%

Sport

- 50%

24" R

ec

Comm

-50%

& 2

4" R

ec

1.5

X Tot

al F &

24"

Rec

SS

BR

S. L. Huron Projection Scenarios

Page 24: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Southhampton

Goderich, ON, CA

Alpena, MI, USA

Tawas

Harrisvi NFL or NHL??Bud or LaBatt’s??So many choices.

Page 25: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

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Gillnet returns of CWT LT from Six Fathom Bank

Page 26: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Summary1) The management strategy now in place in the main

basin of Lake Huron may allow for the rehabilitation of lake trout stocks by 2020.

2) Control of sea lamprey and fishing mortality is necessary for rehabilitation to progress.

3) Cooperative management between USA, 1836 tribes, and Canada is needed to control lake trout mortality in the main basin of Lake Huron.

Page 27: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Summary (cont.)

4) The modeling subcommittee of the Technical Fisheries Committee will update the SCAA models yearly to set TAC’s and monitor progress towards rehabilitation.

We are updating models with data through the year 2000 right now. Preliminary TAC’s are due next week.

Page 28: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Thank God we all made it out in time. ‘Course, now we’re equally screwed.

Page 29: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Thank God we all made it out in time. ‘Course, now we’re equally screwed.

Page 30: Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections Aaron Woldt--MDNR Alpena

Southhampton

Goderich, ON, CA

Alpena, MI, USA

Tawas

Harrisvi ANY QUESTIONS?