study 466 trawl update - 2003 mt. clemens fisheries research station prepared for the saginaw bay...
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Study 466 Trawl Update - 2003Study 466 Trawl Update - 2003
Mt. Clemens Fisheries Research StationPrepared for the Saginaw Bay Coordination Meeting - Feb. 26, 2003
Spottail shiner was the most abundant species in the 2002 fall trawls, with
32,931 captured for a mean cpue of 967 fish per 10
minute tow.
Study Objective: To assess responses of the Saginaw Bay fish community to changing environmental and biological conditions. Of specific interest is the monitoring of fish community responses to management actions and the effects of nonnative species and the gauging of walleye recruitment and population growth.
AuGres
Caseville
Bay City
Locations of 2002 fall trawls on Saginaw Bay - DJ466
•2002 tows in yellow - total of 37 trawl tows at 11 Inner Bay grids
•Total tow time of 249 minutes
•Two outer bay stations (45 and 65 foot depths)
•Magenta 2002
•Yellow 2001
•Green 2000
Mean secchi depth for SB fall trawl surveysMean secchi depth for SB fall trawl surveys(Inner Bay Only)(Inner Bay Only)
No statistically significant trend in secchi depths.
R2 = 0.0024
0.00
0.50
1.00
1.50
2.00
19
87
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90
19
92
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98
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00
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02
De
pth
(m
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AuGres
Caseville
Bay City
Mean Secchi Depths by GridsMean Secchi Depths by Grids
•Magenta=2002
•Yellow=2001
•Green=2000
•Data presented in meters
0
500
1000
1500
2000
2500
Cat
ch/1
0 m
inu
te t
ow
Spottail shiner Trout-perch Alewife Smelt
Thirty-two Year Data Time Series of Fall Thirty-two Year Data Time Series of Fall Trawl CPUE for 4 soft-rayed forage speciesTrawl CPUE for 4 soft-rayed forage species
Comparison of Decade Mean CPUE for primary species captured in fall trawls on Saginaw Bay
0
200
400
600
800
1000
1200YO
Y YP
YAO_Y
P
SMELT
SPOT
TPERCH
ALE
WPERCH
Me
an
CP
UE
by
de
ca
de
70's
80's
90's
00-02
AB
ACBC
CA
B
AB
A
A
Comparison of Decade Mean CPUE for primary species captured in fall trawls on Saginaw Bay
0
10
20
30
40
50
60
70
GSHAD
EMER
WSUCK
WBASS
CHCAT
DRUM
CARP
WALL
EYE
JDART
Me
an
CP
UE
by
de
ca
de
70's
80's
90's
00-02
A
A
A
AAB
A
B
AB AB A
AB
B
0
5001000
1500
20002500
3000
35004000
4500
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
Ca
tch
/10
min
ute
to
w
Round goby Trout-perch Spottail shinerSmelt Gizzard shad Alewife
6 out of the 7 highest totals for soft-rayed forage abundance have occurred since ZM’s colonized the Bay
Catch rates for the common soft-rayed forage species in Saginaw Bay fall trawl surveys
385.3
0
50
100
150
200
250
300
350
400
450
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89
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98
20
01
Ro
un
d g
ob
y C
PU
E
0
5
10
15
20
25
30
35
Jo
hn
ny
da
rte
r C
PU
E
Round goby Johnny darter
Round goby catch rates declined slightly in 2002 – only 1 johnny darter caught in 35 trawl tows
Length frequency distribution for round Length frequency distribution for round goby from SB 2002 trawls goby from SB 2002 trawls
0%
2%
4%
6%
8%
10%
12%2
0
26
32
38
44
50
56
62
68
74
80
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98
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11
0
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Mm group
Pe
rce
nt
of
ca
tch
LSC (n=203) SB (n=454)
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AuGres
Caseville
Bay City
754
659
521
Round goby mean CPUE by grid for fall trawls
•Blue=1999, Green=2000, Yellow=2001, Magenta=2002
•Increasing trend at all grids sampled
•Highest cpue near Sag R.
Zm's, 2%
Unid. Fish, 64%
Rgoby, 60%
Yperch, 6%
Gshad, 4%
Spottail, 2%
Wperch, 2%
Diet of Freshwater Drum from Saginaw BayDiet of Freshwater Drum from Saginaw Bay(expressed as frequency of occurrence)(expressed as frequency of occurrence)
•Samples collected in trawls, Sept. 2002
•88 fish examined
•Total of 50 non-empty stomachs
Spottail, 10%
Wperch, 10%
Other, 10%
Unid. Fish, 10%
Rgoby, 80%
Diet of Channel Catfish from Saginaw BayDiet of Channel Catfish from Saginaw Bay(expressed as frequency of occurrence)(expressed as frequency of occurrence)
•Samples collected in trawls, Sept. 2002
•19 fish examined
•Total of 10 non-empty stomachs
Unid. Fish, 56%
Rgoby, 8%
Yperch, 4%
Gshad, 4%
Spottail, 8% Wperch, 4%
Alewife, 28%
Diet of YAO Walleye from Saginaw BayDiet of YAO Walleye from Saginaw Bay(expressed as frequency of occurrence)(expressed as frequency of occurrence)
•Samples collected in trawls, Sept. 2002
•33 fish examined
•Total of 25 non-empty stomachs
Catch rates for the common spiny-rayed forage species in Saginaw Bay fall trawl surveys
0
500
1000
1500
2000
2500
300019
71
1975
1979
1983
1987
1991
1995
1999
Ca
tch
/10
min
ute
to
w
YOY yellow perch White perch
SB Forage index and total biomass based on fall trawlsSB Forage index and total biomass based on fall trawlsForage index (#/tow)
0
500
1000
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2500
3000
3500
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4500
5000
1971 1975 1979 1983 1987 1991 1995 1999
Forage index (kg/tow)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
1971 1975 1979 1983 1987 1991 1995 1999
Total biomass (kg/tow)
0.0
20.0
40.0
60.0
80.0
100.0
120.0
1971 1975 1979 1983 1987 1991 1995 1999
Forage index species include: Alewife, Emerald shiner, Gizzard Shad, Smelt, Spottail shiner, Round goby, Trout-perch, White bass, White perch, Age 0 Yellow Perch
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AuGres
Caseville
Bay City
11
Age 0 walleye mean CPUE by Grid - 2002
•A total of 84 Age 0 walleye captured in fall 2002 trawls
•Yellow indicates Zero grids
0
200
400
600
800
1,000
1,200
1,40019
86
1987
1988
1989
1990
1991
1992
1993
1994
1995
*
1996
1997
1998
1999
2000
2001
2002
Fin
ge
rlin
gs
pla
nte
d X
1,0
00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
Ag
e 0
wa
lley
e p
er
10
min
ute
s
Fingerlings stocked in SB Catch per 10 minutes
2002 trawl CPUE of 2.54 per 10 minute tow expands out to an estimated bay population of 838,888 Age 0 walleye
Age 0 Walleye CPUE for SB Fall Trawls and Walleye Fingerlings Stocked in SB
Mean CPUE for Age 0 and Yearling+ Yellow Perch in Fall Trawls
0
100
200
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400
500
600
700
800
19
70
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72
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74
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Ca
tch
pe
r 1
0 m
inu
te t
ow
Yearling+ YOY
•Ranked year classes based on mean Age 0 YP CPUE for fall trawls
•Categorized as strong, moderate, or weak, based on natural breaks in the dataset
•1 strong, 3 moderate, and 6 weak cohorts in last 10 years
•2002 is a “weak” yearclass
SB Yellow Perch Year Classes Ranked by YOY Mean CPUE Year YOY CPUE Rank Age 1+ CPUE Total YP CPUE YOY Mean length
1982 686.7 1 632.3 1319.0 76.2 1989 252.8 2 546.2 799.0 71.1 1983 251.9 3 132.1 384.0 76.2 1975 247.9 4 325.1 573.0 88.9 1984 171.0 5 273.0 444.0 78.7 1979 166.7 6 494.3 661.0 78.7 1985 147.8 7 214.2 362.0 78.7 1987 131.5 8 344.5 476.0 81.3
ST
RO
NG
2001 121.6 9 23.6 145.2 76.8
1991 102.6 10 89.1 191.8 71.7 1995 100.8 11 23.9 124.7 72.9 1978 99.8 12 186.2 286.0 86.4 1997 87.4 13 34.4 121.8 74.0 1998 74.4 14 99.2 173.6 76.1 1986 71.4 15 348.6 420.0 73.7 1981 71.3 16 321.7 393.0 83.8 1988 56.6 17 201.4 258.0 76.2
MO
DE
RA
TE
1977 52.9 18 339.1 392.0 91.4
1980 39.0 19 664.0 703.0 86.4 1990 39.0 20 112.0 151.0 79.5 1996 37.8 21 47.5 85.3 81.9 2002 30.7 22 35.8 66.5 76.3 1973 30.6 23 73.4 104.0 91.4 1970 29.5 24 229.0 258.5 96.5 1974 27.9 25 228.1 256.0 88.9 1971 20.2 26 175.8 196.0 91.4 1999 19.5 27 90.9 110.4 92.4 1972 13.9 28 137.1 151.0 83.8 1976 11.1 29 260.9 272.0 91.4 2000 8.6 30 28.1 36.7 83.2 1992 7.7 31 67.2 74.9 74.1
WE
AK
1994 3.9 32 20.3 24.2 85.0 1993 0.5 33 40.0 40.5 90.7
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AuGres
Caseville
Bay City
110
YOY YP mean CPUE by grid
•Green=2000 (8.6)
•Yellow=2001 (121.6)
•Magenta=2002 (30.7)
•Highest 2002 YOY densities at Grid 115
Mean length at age for SB YPMean length at age for SB YP
Sta
te.a
vg.
1987
1989
1991
1993
1995
1997
1999
2001
100120140160180200220240
To
tal l
en
gth
(m
m)
Age 3 Age 4
0.0%
5.0%
10.0%
15.0%
20.0%
25.0%
per
cen
t
1986
1988
1990
1992
1994
1996
1998
2000
Proportion of 8" and larger perch in fall trawl tows
Lower abundance, faster growth, higher proportion of harvestable fish
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
Po
un
ds
per
net
lif
t
0
100
200
300
400
500
600
700
Fis
h p
er 1
0 m
inu
te t
ow
Comm C/E Annual Trawl YAO CPUE
Commercial fishery catch rates and annual trawl YAO YP cpue for SB
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
Po
un
ds
per
net
lif
t
0
50000
100000
150000
200000
250000
300000
350000
Po
un
ds
of
fish
per
yea
r
Comm C/E Annual total catch
Comm. fishery catch rates and total annual comm. YP catch for SB
Mt. Clemens Plans for SB 2003 Sampling
•Trawl survey in September
•Sample Inner Bay and Outer Bay sites
•Collect carp pathology samples if available
•Sample commercial fishery yellow perch for length, wt, age