Design and Implementation of a Fishery-Independent Shallow Water Trawl Survey for Maryland

1
Design and Implementation of a Fishery-Independent
Shallow Water Trawl Survey for Marylands
Portion of Chesapeake Bay
Brandon Muffley and Alexei Sharov MD Dept. of
Natural Resources, Fisheries Service Annapolis, MD
2
Design and Implementation of a Fishery-Independent
Shallow Water Trawl Survey for Marylands
Portion of Chesapeake Bay
Brandon Muffley and Alexei Sharov MD Dept. of
Natural Resources, Fisheries Service Annapolis, MD
3
Background

• 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 survey

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

4
Shoal Survey Design
2001 4 Strata 108 Stations 3 Sampling
Periods 6 minute trawls
Surveys conducted in four mid-Bay strata, chosen
for compatibility with broad scale efforts, and
with existing surveys

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

5
Shoal Survey Design (con.t)
2002 9 Strata 120 Stations 3 Sampling
Periods 6 minute trawls
S9
S7
Annapolis
S6
S8
Surveys conducted in nine mid upper Bay strata,
chosen for compatibility with broad scale
efforts, and with existing surveys
S5

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

6
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.

7
Summary Statistics
2001 May July September Total
of Trawls 103 108 107 318
of Fish 2358 8754 4630 15742
Total Weight (kg) 34.8 40.2 82.1 157.1
of Species 22 22 22 36
2002 May July September Total
of Trawls 118 113 120 351
of Fish 1837 2477 3061 7375
Total Weight (kg) 29.2 66.5 117.7 213.3
of Species 23 27 25 34
8
Species Caught
July 2002
American Eel Northern Searobin Atlantic
Silverside Oyster Toadfish Bay
Anchovy Pigfish Blackcheek Tonguefish Silver
Perch Blue Crab Skilletfish Croaker Spot H
arvestfish Spotted Seatrout Hogchoker Strip
ed Bass Horseshoe Crab Summer
Flounder Lizardfish Weakfish Naked
Goby White Perch Northern Kingfish Windowpane
Flounder Northern Pipefish Winter
Flounder Northern Puffer
9
Yearly Distribution of Abundance
10
Yearly Distribution of Biomass
11
Seasonal Distribution of Biomass
12
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
13
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
14
Abundance Trends
Tangier Sound Blue Crab

• MD DNR crab trawl survey ChesFIMS 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

15
Biological Characteristics
Bay Anchovy
Mean Length (mm) May 67.2

• Size and size-at-age
• Growth rates

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

For a number of species
16
Biological Characteristics
Bay Anchovy
Mean Length (mm) May 67.2 July
43.9

• Size and size-at-age
• Growth rates

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

For a number of species
17
Biological Characteristics
Bay Anchovy
Mean Length (mm) May 67.2 July
43.9
Sept 48.1

• Size and size-at-age
• Growth rates

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

For a number of species
18
Biological Characteristics
May Mean Length (mm) 60.3

• For A Number of Species
• Size and size-at-age
• Growth rates
• Habitat preferences/associations
• (adults juveniles)
• Recruitment

July Mean Length (mm) 95.6
Sept. Mean Length (mm) 115.2
Blue Crab
19
Biological Characteristics
Blue Crab
Mean Length (mm) May 60.3

• Size and size-at-age
• Growth rates

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

For a number of species
20
Biological Characteristics
Blue Crab
Mean Length (mm) May 60.3
July 95.6

• Size and size-at-age
• Growth rates

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

For a number of species
21
Biological Characteristics
Blue Crab
Mean Length (mm) May 60.3 July
95.6
Sept 115.2

• Size and size-at-age
• Growth rates

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

For a number of species
22
Species Diversity
By Strata
Species Diversity vs. Species Richness
23
Species Diversity
By Season
Species Diversity vs. Species Richness
24
Species Diversity
By Year
Species Diversity vs. Species Richness
25
Gear Comparison Study
Why needed Allow both surveys to be
combined Estimate small scale spatial and
temporal covariation Different sampling
scheme Different gear fishing efficiencies
26
Diet Analysis
Season
Strata Spring Summer Fall Total
Chester 7 14 0 21
Eastern Bay 0 2 0 2
Choptank 0 10 0 10
Little Choptank 0 2 0 2
Tangier 28 94 48 170
Pocomoke 24 74 4 102
Patapsco 52 55 30 137
Severn/South 42 39 2 83
Calvert Cliffs 0 11 0 11
Season Total 153 301 84 538
Species Collected Croaker
Spot Weakfish Hogchoker
Striped bass White perch Northern
Kingfish A. Silverside
Trophic Linkages Predator prey Multispecies
models Bioenergetic models
27
Sample Diets

• Gut contents flushed, sample split, taxa
  identified,
• weighed and counted

(from Miller et. al. 2001)
0.4
0.67
0.00
0.00
0.00
0.04
0.00
0.00
0.00
0.00
0.00
0.04
0.00
0.04
0.04
0.00
0.00
0.04
0.00
0.00
0.08
0.00
0.00
0.04
0.00
0.00
0.00
0.08
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.04
0.46
0.00
0.00
0.3
Striped Bass - Upper Bay (n 24)
0.2
Percent Weight ( W)
0.1
0
Egg
Bivalve
Fish
Crab
Insect
Mysid
Isopod
Diptera
Mussel
Annelid
Shrimp
Worm
Fish Egg
Tunicate
Blue Crab
Fish Part
Copepod
Barnacle
Clupeid Egg
Polychaete
Flatworm
Nematode
Amphipod
Insect Egg
Nemertean
Cumacean
Insect Larvae
Gastropod
Chironomidae
Grass Shrimp
Nudibranch
Razor Clam
Unidentified
Unidentified
Organic Matter
Tube Worm
Copepod Egg
Gastropod Egg
Gnathostomulid
Unidentified
Skeleton
Unidentified
Unidentified
Unidentified
Unidentified
Unidentified
Prey Item
28
Summary

• 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 Temporally extensive Species rich

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

29
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