status of lake trout in lake superior 1993-2000 shawn sitar, midnr; chuck bronte, usfws; mark...
TRANSCRIPT
Status of lake trout in Lake Superior1993-2000
Shawn Sitar, MIDNR; Chuck Bronte, USFWS; Mark Ebener, CORA; Tom Fratt, RCFD; Ken Gebhardt, BMIC; Ted Halpern, MNDNR; Bill Mattes, GLIFWC; Gene Mensch, KBIC; Mike
Petzold, OMNR; Steve Schram, WIDNR; Don Schreiner, MNDNR.
Fish Community Objective
lake trout
Achieve and maintain genetically diverse self-sustaining populations of lake trout that are similar to those found in the lake prior to 1940, with lean lake trout being the dominant form in near-shore waters, siscowet lake trout the dominant form in offshore waters, and humper lake trout a common form in eastern waters and around Isle Royale.
MN3
MN2
MN1
WI1
WI2MI2
MI1
MI3
MI4
MI5
MI6MI7
MI8
1
32 33
313027
29
28
25 26
2422
1621 2315
149 13 17 20
191812
10 117
6
5
42 3
34
Lake trout management units in Lake Superior
1950 1960 1970 1980 1990 2000
Year
0
1
2
3
4
Mil
lio
ns
sto
cked
Lake trout stocking in Lake Superior
Relative abundance of lake trout in Lake Superior, 1993-2000
0102030405060708090
100
ON-1
ON-5
ON-9
ON-11
MN-1
MN-2
MN-3
WI-1
WI-2
MI-2
MI-3
MI-4
MI-5
MI-6
MI-7
MI-8
ON-24
ON-26
ON-28
ON-31
ON-33
ON-34
Management Unit
0102030405060708090
100
GM
CP
UE
(fis
h/km
/nig
ht)
Wild
Hatchery
153.1
Relative abundance of wild lake trout in Lake Superior, 1993-2000
GM
CP
UE
(fis
h/km
/nig
ht)
Management Unit
0
10
20
30
40
50
60
70
80
90
100ON-1
ON-5
ON-9
ON-11
MN-1
MN-2
MN-3
WI-1
WI-2
MI-2
MI-3
MI-4
MI-5
MI-6
MI-7
MI-8
ON-24
ON-26
ON-28
ON-31
ON-33
ON-34
153.1
Relative abundance of hatchery lake trout in Lake Superior, 1993-2000
Management Unit
GM
CP
UE
(fis
h/km
/nig
ht)
0
5
10
15
20
25
30
35
40ON-1
ON-5
ON-9
ON-11
MN-1
MN-2
MN-3
WI-1
WI-2
MI-2
MI-3
MI-4
MI-5
MI-6
MI-7
MI-8
ON-24
ON-26
ON-28
ON-31
ON-33
ON-34
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7ON-1
ON-14
MN-1
MN-2
MN-3
WI-1
WI-2
MI-2
MI-3
MI-4
MI-5
MI-6
MI-7
ON-24
ON-28
ON-31
ON-33
Management Unit
To
tal A
nn
ual
Mo
rtal
ity
Total annual mortality for lake trout in Lake Superior 1993-2000(catch curves)
0
0.5
1
1.5
2
2.5
3
3.5
4
1867 1877 1887 1897 1907 1917 1927 1937 1947 1957 1967 1977 1987 1997
Year
Canada
U.S.
Yie
ld (
mil
lio
n k
g)
Lean lake trout commercial yield in Lake Superior, 1867-2000
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
1993 1994 1995 1996 1997 1998 1999 2000 1929-43
Year
CanadaMinnesota Wisconsin Michigan
Yie
ld (
x 1,
000
kg)
Recent commercial harvest of lake trout in Lake Superior
Avg. 1983-92
Recreational harvest of lake trout in Lake Superior, 1970-1999
Year
80,000
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998
Michigan
Wisconsin
Minnesota
Nu
mb
er o
f fi
sh
Sea Lamprey Marking of Lean Lake TroutLake Superior, 1986-2000
1986 1988 1990 1992 1994 1996 1998 2000
0
2
4
6
8
10
Mar
ks p
er
100
Fis
h
Average 1986-99
1986 1988 1990 1992 1994 1996 1998 2000
Year
0
2
4
6
8
10
12
Mar
ks
per
100
Lak
e T
rou
t
Canada
U. S.
Lamprey Marking of Lake Trout Lake Superior, 1986-2000
Sea Lamprey Marking East & West U. S. Waters Lake Superior 1986-2000
1986 1988 1990 1992 1994 1996 1998 2000
Year
0
5
10
15
Mar
ks
per
100
Lak
e T
rou
t
West
East
Lake trout yield to sea lampreys and humans in Lake Superior during 1993-2000
Year
Bio
mas
s (x
100
0 k
g)
0
100
200
300
400
500
600
700
800
900
1,000
1,100
1,200
1993 1994 1995 1996 1997 1998 1999 2000 1983-92(avg.)
HumansSea lampreys
4550
55
60
65
70
4550
55
60
65
70
TO
TA
L L
EN
GT
H (
cm)
Michigan (MI-3 - MI-7)
Wisconsin (WI-2)
1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992
YEAR
45
50
55
60
65
70Minnesota (MN-1 - MN-3)
Planted
Wild
Wild
Planted
Planted
From Hansen et al. (1994)
Mean length of age 7 lake trout in US waters of Lake Superior, 1970-92
Mean length at age 7 for lake trout in Lake Superior, 1993-2000
ONTARIO-E ONTARIO -WMINNESOTA
WISCONSINMICHIGAN
HATCHERY
WILD
TO
TA
L LE
NG
TH
(m
m)
480
500
520
540
560
580
600
620
Siscowet
CP
UE
(K
g/km
net
)
1950 1960 1970 1980 1990 20000
100
200
300
400
500 Canadian Offshore (> 80 m) commercial fishery
Relative abundance of siscowets in commercial fisheries
1950 1960 1970 1980 19900
50
100
150
200
250
300U.S. commercial fisheries
Jun-96Aug-97
Jun-00 0-119
120-239
240-359
360-479
480-599
>599
0.05.0
10.015.020.025.030.035.040.045.0
Date
Depth Bin (ft)
CP
UE
(fi
sh/3
05 m
) Jun-96Aug-97
Jun-00 0-119
120-239
240-359
360-479
480-599>599
0.05.0
10.015.020.025.030.035.040.045.0
Relative abundance of siscowets in Lake Superior(Agency surveys)
Siscowet
Lean
Date
MN-1 MI-2 MI-4 MI-5 MI-7
Management Unit
0
5
10
15
20
25
Fis
h /3
05 m
Lean
Siscowet
16:1
12:1
2:1
18:1
13:1
Mean = 14:1
Ratio of siscowets to leans by management unit
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35
Age (yr)
0
5
10
15
20
25
30
Nu
mb
er o
f fi
sh
MI-4
MI-7
MI-2
Age compositions of siscowet by management unit in 1996
Recent analyses of lake trout dynamics in Michigan waters of Lake Superior
• Statistical catch-at-age models for wild lake trout in MI-5, MI-6, and MI-7 (MSC, TFC)
• Stock-Recruitment analyses for lake trout in MI-3 through MI-7 (Jessica Richards)
• Comparison of historic and modern abundance in Michigan waters (Mike Wilberg)
Statistical catch-at-age models
• GLFC workshops.
• Models integrate age-specific data from diverse
sources.
• Models used in 1836 Treaty waters to estimate
quotas.
0
200
400
600
800
1,000
1,200
1,400
1,600
1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
Year
MI-5
MI-6
MI-7
Wild lake trout abundance (ages 3+)N
umbe
r of
fis
h x
1,00
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
Year
MI-5MI-6MI-7
Target maximum
Tot
al M
orta
lity
Rat
eTotal annual mortality rates for ages 6-11 lake trout
Mortality rates for ages 6-11 wild lake trout in MI-5In
stan
tan
eou
s m
orta
lity
(yea
r-1)
Year0
0.05
0.1
0.15
0.2
1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
Sea LampreyCommercial FishingRecreational FishingNatural
Mortality rates for ages 6-11 wild lake trout in MI-6In
stan
tan
eou
s m
orta
lity
(yea
r-1)
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
Year
Sea lampreyCommercial FishingRecreational FishingNatural
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
Year
Sea LampreyCommercial FishingRecreational FishingNatural
Mortality rates for ages 6-11 wild lake trout in MI-7In
stan
tan
eou
s m
orta
lity
(yea
r-1)
Spawning stock biomass to project safe harvest levels
• SSBR=the theoretical amount of mature female
biomass produced per given recruit through its life.
• SSBR Target =The total amount of spawning stock
biomass produced per recruit that suffers the target
maximum mortality
• The SSBR values will vary over time as the
mortality and maturity schedules vary over time.
0.0
0.1
0.2
0.3
0.4
0.5
0.6
MI-5 MI-6 MI-7
Management Unit
Avg. 1998-2000Target
SS
BR
(k
g)
Spawning stock biomass
50 100 200
0
5
10
15
20
25
30
10
15
20
25
30
150
Parental Stock CPE
10
15
20
25
30
10
15
20
25
30
10
15
20
25
30
Rec
ruit
men
t C
PE
MI-5
MI-4
MI-6
MI-7
MI-3
From: Doemel (2000)
Lake trout stock-recruitment relationships in Michigan(Based on 1970-98 data)
Historic and Modern lake trout relative abundance
MI-2 MI-3 MI-4 MI-5 MI-6 MI-7 MI-8
CPUE 1984-98 40.5 8.1 14.8 39.7 20.8 11.1 1.3
Historic CPUE (1929-43)
7.2 7.4 6.8 9.0 8.1 16.1 19.6
From: Wilberg (2000)
Status of lake trout in Lake Superior 2000
• Wild lake trout abundance increasing MN & WI and high levels
MI waters
• Current abundance MI higher than historic values
– recruitment peaked recently
– indications of density dependence most areas.
• Growth rates continue to decline and began in 1970s.
• Siscowet abundance high & may be increasing
• Sea lampreys kill more lake trout than fisheries.
Recommendations• Further develop & evaluate statistical population
models
• Quantify movement patterns.
• Evaluate FCOs and reference points.
• Monitor and assess siscowet populations.
• Expand understanding of lake trout forms.
• Develop bioenergetics models to assess food web
stability.
• Map and quantify lake trout habitat.