Design and Implementation of a Fishery-Independent Shallow Water

Trawl Survey for Maryland’s Portion of Chesapeake Bay

Brandon Muffley and Alexei Sharov

MD Dept. of Natural Resources, Fisheries ServiceAnnapolis, MD

Background

• Why needed ?Why needed ?– Chesapeake 2000 commitment to multispecies approaches– Past/current studies lack spatial and temporal coverage needed– Few studies incorporate shoal (shallow) areas– Wide range of information gained on a variety of economically & ecologically important species

• ChesFIMS surveyChesFIMS survey Broad scale survey – mid-water trawls in mainstem of C. B. Shoal survey – bottom trawl in shallow waters of MD C. B.

Solomons

Shoal Survey Design

• Stratified random design• Proportional station allocation• Trawl design from MD DNR crab survey

Surveys conducted in four mid-Bay strata, chosen for compatibility with broad scale efforts, and with existing surveys

20014 Strata108 Stations3 Sampling Periods6 minute trawls

S1

S2

S3

S4

Solomons

Shoal Survey Design (con.t)

• Stratified random design• Proportional station allocation based on variance estimates

Surveys conducted in nine mid & upper Bay strata, chosen for compatibility with broad scale efforts, and with existing surveys

20029 Strata120 Stations3 Sampling Periods6 minute trawls

S5

S6

S7

S8

S9

Annapolis

Data Collection

Biological Information• Species ID• Length (TL)• Weight• Sex (blue crab)• Gut content

Water Quality• Temperature• DO• Salinity• Depth• Secchi

Misc. Information• Tide State• Bottom Substrate• Boat Speed/RPM• Position Coordinates• Air Temp.

Summary Statistics2001 May July September Total

# of Trawls 103 108 107 318318

# of Fish 2358 8754 4630 1574215742

Total Weight (kg)

34.8 40.2 82.1 157.1157.1

# of Species 22 22 22 3636

2002 May July September Total

# of Trawls 118 113 120 351351

# of Fish 1837 2477 3061 73757375

Total Weight (kg)

29.2 66.5 117.7 213.3213.3

# of Species 23 27 25 3434

Species Caught

American Eel Northern Searobin Atlantic Silverside Oyster Toadfish Bay Anchovy PigfishBlackcheek Tonguefish Silver Perch Blue Crab SkilletfishCroaker SpotHarvestfish Spotted Seatrout Hogchoker Striped Bass Horseshoe Crab Summer FlounderLizardfish Weakfish Naked Goby White PerchNorthern Kingfish Windowpane FlounderNorthern Pipefish Winter FlounderNorthern Puffer

July 2002

Yearly Distribution of Abundance

0 - 1011 - 2526 - 5051 - 100101 - 1200

3 0 3 6 Miles

N

2001 Total N

SolomonsSolomons

0 - 1011 - 2526 - 5051 - 100101 - 1200

3 0 3 6 Miles

N

Total N2002

SolomonsSolomons

Yearly Distribution of Biomass

N

5 0 5 Miles

0 - 100101 - 500501 - 10001001 - 30003001 - 60006001 - 1000010001 - 17000

2001 Total g

SolomonsSolomons

6 0 6 Miles

N

10001 - 170006001 - 100003001 - 60001001 - 3000501 - 1000101 - 5000 - 100

2002

SolomonsSolomons

Total g

Overall Catch Tow -1 by Species

July 2001 September 2001

Bay Anchovy Blue Crab White Perch

Croaker Spot Striped Bass

Hogchoker Summer Flounder Weakfish

Lizardfish N. Kingfish Other

Overall Biomass Tow –1 by Species

July 2001 September 2001

Bay Anchovy Blue Crab White Perch

Croaker Spot Striped Bass

Hogchoker Summer Flounder Weakfish

Lizardfish N. Kingfish Other

Abundance Trends

0

20

40

60

80

1990 1992 1994 1996 1998 2000 2002 2004

mea

n C

atch

to

w-1 May July September

Tangier Sound – Blue Crab

MD DNR crab trawl surveyMD DNR crab trawl survey ChesFIMS shoal surveyChesFIMS shoal survey• Fixed stations * Stratified random stations• Few stations * Numerous stations• 16’ semiballoon otter trawl * 16’ semiballoon otter trawl• 6 minute tows * 6 minute tows

5 different strata sampled by both surveys

                                                                                                                                                               

0

50

100

150

200

250

300

350

400

450

15-20

20-25

26-30

31-35

36-40

41-45

46-50

51-55

56-60

61-65

66-70

71-75

76-80

81-85

86-90

91-95

Length (mm)

Fre

qu

ency

May

Biological CharacteristicsMean Length (mm)

May 67.2

• Size and size-at-age • Growth rates

• Habitat Preferences/Associations (adults & juveniles)• Recruitment

Bay AnchovyBay Anchovy

* For a number of species

0

50

100

150

200

250

300

350

400

450

15-20

20-25

26-30

31-35

36-40

41-45

46-50

51-55

56-60

61-65

66-70

71-75

76-80

81-85

86-90

91-95

Length (mm)

Fre

qu

ency

May July

Biological CharacteristicsMean Length (mm)

May 67.2

July 43.9

• Size and size-at-age • Growth rates

• Habitat Preferences/Associations (adults & juveniles)• Recruitment

Bay AnchovyBay Anchovy

* For a number of species

0

50

100

150

200

250

300

350

400

450

15-20

20-25

26-30

31-35

36-40

41-45

46-50

51-55

56-60

61-65

66-70

71-75

76-80

81-85

86-90

91-95

Length (mm)

Fre

qu

ency

May July September

Biological CharacteristicsMean Length (mm)

May 67.2

July 43.9

Sept 48.1

• Size and size-at-age • Growth rates

• Habitat Preferences/Associations (adults & juveniles)• Recruitment

Bay AnchovyBay Anchovy

* For a number of species

Species Diversity

By StrataBy Strata

Species Diversity vs. Species Richness

0

1

2

3

4

5

6

7

Sp

ecie

s t

raw

l-1

September 2002

6 68

13

22

189

11 11

25

Species Diversity

By SeasonBy Season

Species Diversity vs. Species Richness

0

1

2

3

4

5

6

LittleChoptank

Tangier Pocomoke CalvertCliffs

Overall

Sp

ec

ies

tra

wl-1

May July September All 2001

2222

22

Species Diversity

By YearBy Year

Species Diversity vs. Species Richness

0

1

2

3

4

5

6

Little Choptank Tangier Pocomoke Calvert Cliffs Overall

Sp

ecie

s tr

awl-

1

2001 2002 July 01 & 02

7

19 15

11

27228

16

15

2

Gear Comparison Study

0

10

20

30

40

50

60

70

80

90

100

Deep Stations(8m)

ShallowStations (4m)

Day Trawls Night Trawls Overall

me

an

Ca

tch

to

w-1

Why needed:Why needed:* Allow both surveys to be combined* Estimate small scale spatial and temporal covariation* Different sampling scheme* Different gear – fishing efficiencies

Diet AnalysisSeason

Strata Spring Summer Fall Total

Chester 7 14 0 2121

Eastern Bay 0 2 0 22

Choptank 0 10 0 1010

Little Choptank

0 2 0 22

Tangier 28 94 48 170170

Pocomoke 24 74 4 102102

Patapsco 52 55 30 137137

Severn/South 42 39 2 8383

Calvert Cliffs 0 11 0 1111

Season Total 153153 301301 8484 538538

Species Collected Croaker Spot Weakfish Hogchoker Striped bass White perch Northern Kingfish A. Silverside

Trophic LinkagesPredator – preyMultispecies modelsBioenergetic models

Sample Diets Gut contents flushed, sample split, taxa identified, weighed and counted

0.6

7

0.0

0

0.0

0

0.0

0

0.0

4

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

4

0.0

0

0.0

4

0.0

4

0.0

0

0.0

0

0.0

4

0.0

0

0.0

0

0.0

8

0.0

0

0.0

0

0.0

4

0.0

0

0.0

0

0.0

0

0.0

8

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

4

0.4

6

0.0

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0.0

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0.1

0.2

0.3

0.4

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Per

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(% W

)

Prey Item

(from Miller et. al. 2001)

Striped Bass - Upper Bay (n = 24)

SummaryInformation Gained:Information Gained:

• Survey design and implementation• CPUE and Biomass estimates• Species abundance and distribution• Life history characteristics (i.e. growth and habitat use)• Species diversity and richness• Recruitment• Trophic linkages – gut analysis• Time series of abundance

Management Implications

Spatially&

Temporallyextensive

Species rich

Other Areas of Interest:Other Areas of Interest:• Water quality• Trawl time• Volumetric analysis / gear comparison

Acknowledgements•Project funded by CBSAC through NOAA CB Office

• Nate Herman• Tom Miller • Jon Volstad• Phil Jones• Dale Weinrich• Paul Genovese• Harry Rickabaugh• Keith Witeford• Mark Matsche• Tony Jarzynski• Jim Mower• Bob Sadzinski

• Marek Topolski• Harley Speir• Harry Hornick• Butch Webb• Bruce Pyle• Jim Thompson• Kinte Thompson• Kevin Donaldson• Bennie Williams• Jen Ball• Matapeake interns