Study 466 Trawl Update - 2003 Mt. Clemens Fisheries Research Station Prepared for the Saginaw Bay...

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

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87

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92

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98

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02

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pth

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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

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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

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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

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70

GSHAD

EMER

WSUCK

WBASS

CHCAT

DRUM

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EYE

JDART

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UE

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5001000

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4500

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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

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250

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450

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y C

PU

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35

Jo

hn

ny

da

rte

r C

PU

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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%

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12%2

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Mm group

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rce

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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)


•19 fish examined


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)


•33 fish examined


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

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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)

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1971 1975 1979 1983 1987 1991 1995 1999

Forage index (kg/tow)

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1971 1975 1979 1983 1987 1991 1995 1999

Total biomass (kg/tow)

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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

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1,000

1,200

1,40019

86

1987

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1995

*

1996

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2002

Fin

ge

rlin

gs

pla

nte

d X

1,0

00

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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

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800

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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

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1993

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1997

1999

2001

100120140160180200220240

To

tal l

en

gth

(m

m)

Age 3 Age 4

0.0%

5.0%

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15.0%

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25.0%

per

cen

t

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Proportion of 8" and larger perch in fall trawl tows

Lower abundance, faster growth, higher proportion of harvestable fish

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Comm C/E Annual Trawl YAO CPUE

Commercial fishery catch rates and annual trawl YAO YP cpue for SB

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yea

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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

Study 466 Trawl Update - 2003 Mt. Clemens Fisheries Research Station Prepared for the Saginaw Bay...

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