Status of Lake Trout(Salvelinus namaycush)

in Georgian Bay and North Channel

Lloyd C. Mohr

Upper Great Lakes Management Unit,

Lake Huron Office, OMNR

Owen Sound, ON

Background

Statistical Districts in Cdn Waters

Data Sources: - Commercial Harvest - Commercial Catch Sampling - Index Assessment Surveys - Recreational Surveys

LakeTrout Rehabilitation

1996 Rehab Plan

7 Active Rehab Zones

2 Proposed Sanctuaries

LakeTrout Rehabilitation

Objectives

Spawning Populations 2005

Natural Reproduction 2010

Self-Reproducing in Former Range 2020Annual sustained yield 1.12 million kg

LakeTrout Sources

• Iroquois Bay• Parry Sound

Remnant Stocks

Lake Trout Sources

11 sites• Average 850K G.Bay• 110K N. Channel• 1991 30% Backcross G. Bay• 1996 Pure Lake Trout

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

2.25

2.5

1979 1982 1985 1988 1991 1994 1997Year

Nu

mb

er S

tock

ed x

10

6 North ChannelGeorgian BayLake Huron

Stocking

Lake Trout SourcesMovement (CWT)

GB09 97.6GB08 2.4

GB10 56.5GB11 14.5GB08 14.2GB09 9.5

GB03 40.4LH03 20.1LH04 27.4GB10 8.8

%

LakeTrout Exploitation - Commercial

0

500

1000

1500

2000

2500

3000

3500

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Year

Ha

rve

st

(kg

x 1

00

0)

U.S. HURON GEO BAY N.CHAN

Prior to 1922, Canadian Harvest combined for all 3 Basins

Annual Harvest

0

20

40

60

80

100

120

140

160

180

200

1970 1974 1978 1982 1986 1990 1994 1998 Year

Har

vest

(kg

x 1

000)

0

500

1000

1500

2000

2500

Fis

h S

tock

ed (

# x1

000)

N.CHAN

GEO BAY

HURON

Number Stocked

LakeTrout Exploitation - CommercialAnnual Harvest

0

20,000

40,000

60,000

80,000

100,000

120,000

1979 1983 1987 1991 1995 1999

Year

Ha

rve

st

(kg

)

NC3

NC2

NC1

GB4

GB3

GB2

GB1

LakeTrout Exploitation - CommercialStatistical Districts

LakeTrout Exploitation - CommercialIncidental Catch

0

20

40

60

80

100

120

140

160

180

Georgian Bay North Channel Main Basin

Nu

mb

er F

ish

/ F

ish

ing

Eve

nt 1975-1979

1980-1990

1991-1999

LakeTrout Exploitation - Commercial

95.7 92.1 87.8

2.9 <0.1 3.6

0.7 6.5 6.6

0.7 1.3 2.1

GB NC MBIncidental Catch (%)

0.0

0.4

0.8

1.2

1.6

2.0

1 2 3 4 5 6 7 8 9 10 11 12Month

kg

Lt

/ k

g L

wf1990 1991 1992 1993

1994 1995 1996 1997

LakeTrout Exploitation - CommercialIncidental Catch (Seasonal)

LakeTrout Exploitation - CommercialIncidental Catch (Spatial)

> 1,000 kg

250 - 1000

100 - 250

10 - 100

< 10

1979 1989

1999

LakeTrout Exploitation - CommercialIncidental Catch (Spatial)

1999

> 1,000 kg

250 - 1000

100 - 250

10 - 100

< 10

0

0.1

0.2

0.3

0.4

0.5

0.6

4.25 4.5 4.75 5 5.25 5.5Mesh size (in.)

Lak

e tr

ou

t /

Lak

e W

hit

efis

h 1992

1993

1994

1995

1996

1997

1998

1999

LakeTrout Exploitation - CommercialIncidental Catch (mesh size)

LakeTrout Exploitation - SportSW Georgian Bay

0

5000

10000

15000

20000

25000

30000

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999

Year

Bio

mas

s (k

g) Georgian Bay

Main Basin

LakeTrout Biological Data

LakeTrout - (Mean Size)Mean Size of Lake Trout Harvested

Georgian Bay

0

500

1000

1500

2000

2500

3000

1989 1991 1993 1995 1997 1999Year

RW

T (

g)

0

100

200

300

400

500

600

FL

EN

(m

m)

RWT

FLEN

Mean Size of Lake Trout HarvestedNorth Channel

0

500

1000

1500

2000

2500

3000

1989 1991 1993 1995 1997 1999Year

RW

T (

g)

0

100

200

300

400

500

600

700

FL

EN

(m

m)

RWT

FLEN

0

1

2

3

4

5

6

1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Year

Ag

e (y

r)

GB

NC

LakeTrout - (Mean Age)Known Age Fish only

0.0

0.1

0.2

0.3

0.4

0.5

1 2 3 4 5 6 7 8 9 10

1989

1999

0.00.1

0.20.3

0.40.5

0.60.7

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

1989

1999Georgian Bay

North Channel

LakeTrout - (Age Distributions)

0

100

200

300

400

500

600

700

800

1988 1990 1992 1994 1996 1998 2000

Year

Ave

rag

e F

LE

N (

mm

)

10

9

8

7

6

5

4

3

2

1

LakeTrout - (Size at Age)Known Age Fish only

North Channel Lake Trout Maturity (Female) 1998-1999

y=exp(-13.80725+(2.628768)*x)/(1+exp(-13.80725+(2.628768)*x))

AGE

M

AT

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7 8 9 10

North Channel50% - 5.3yr

Georgian Bay50% - 4.6 yr

Georgian Bay Lake Trout Maturity (Female) 1998-1999

y=exp(-11.21678+(2.455271)*x)/(1+exp(-11.21678+(2.455271)*x))

AGE

M

AT

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7 8 9 10

LakeTrout - (Maturity Schedule)Females

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

3 4 5 6 7 8 9Age

Pro

po

rtio

n M

atu

re

1991

1992

1993

1994

1995

1996

1997

1998

SW Georgian Bay (females)

LakeTrout - (Maturity Schedule)

0

20

40

60

80

100

1992 1994 1996 1998 2000Year

To

tal A

nn

ual

Mo

rtal

ity

(A)

LakeTrout - (Mortality)

SW Georgian Bay (Age 4+)

LakeTrout - (Sea Lamprey Wounds)

0

10

20

30

40

50

1984 1986 1988 1990 1992 1994 1996 1998

Year

# W

ou

nd

s /

10

0 F

ish

NC

GB

MB

All Data Sources

LakeTrout RehabilitationObjectives

Spawning Populations 2005

Self-Reproducing in Former Range 2020Annual sustained yield 1.12 million kg

Natural Reproduction 2010

Evaluation

• Lake Trout Survival highly variable

• Spawning Stock Size• Egg Deposition• Natural Reproduction• Age Structure• Range• Abundance• Yield

under investigation

unknown

present 2-4 locations

constricted

expansion in P. Sound

CPUE variable

???

LakeTrout Rehabilitation

LakeTrout Management

Exploitation Review •Commercial Quota and Recreational Limits

• Incidental Catch Rates

• Reporting / Assessment Issues

LakeTrout Management

Lake Trout Rehabilitation Plan Review •summarize/evaluate data

• model results

• LTRP Benchmarks

• re-evaluate assessment protocol/requirements

• where are we?

LakeTrout Management