Project Update

Shallow Water Use Studies and Shoreline Inventory

Donna Marie Bilkovic and Marcia Berman

Center for Coastal Resources ManagementVirginia Institute of Marine Science

June 2007

Shallow water use project objectives

1. Assess tidal creek fish community characteristics in Lynnhaven Bay

2. Compare fish communities in dredged andundredged tidal creek systems

3. Inventory shoreline condition in Lynnhaven Bay --

including land use, structures and bank conditions

Coastal development stressors on estuarine communities include

Shoreline hardeningLand use conversionVegetation removal

Dredging

Possible stressors caused from dredging with particular importance to fish

Habitat removal Loss of prey items (e.g. burial of benthos) Increased turbidity Alteration of physical habitat (e.g. sediment, current

patterns, water quality, salinity, reduction in flushing)

What are the recovery rates of fish communities? Research on benthic communities indicates recovery rates are

dependent on several factors including salinity, system size, and sediment grain size. (faster in fine-grained and lower salinity

regions)

Limited research on fish recovery rates in tidal creek systems

Fish Survey Locations:August-October 2006

6 Creeks in the Western Branch(3 dredged; 3 undredged)

Each Creek sampled with multiple gear types;

Monthly

When DredgedNorth Creek: Feb 2006Hebden Creek: Mar 2000Buchanan Creek: Jul 2000

Push NetsBeach Seines

Experimental

Gill nets

Water Qualitymeasures

Multiple facets of the fish communities were targeted with different gear types

For example: nearshore juvenile species—beach seine

0.05 km2

0.09 km2

Dredged Feb 2006

0.6 km2

0.3 km2

Dredged Mar 2000

0.6 km2

4.9 km2

Dredged Jul 2000

2.8

4.3

2.9

4.0

4.3

3.6

Site Tidal Creek State Depth Cond DO NTU pH Salinity Temp 1 North Undredged 2.87 33538 6.90 18.01 7.91 21.17 23.22 2 North Dredged 4.45 33725 7.12 18.42 7.94 21.13 23.24 3 Hebden Undredged 3.18 33768 6.87 38.27 7.79 21.16 24.37 4 Hebden Dredged 4.20 33402 6.59 54.72 7.66 20.90 23.43 5 Buchanan Undredged 3.97 29983 5.66 34.35 7.37 18.59 23.67 6 Buchanan Dredged 3.48 31005 5.81 48.08 7.48 19.35 23.31

Site Characteristics on Average: August-October 2006

Extreme variability in basic water quality measures:e.g. Salinity, Temperature, Dissolved Oxygen, Turbidity

Sal

inity

(pp

t)

10/1

9/06

10/1

3/06

10/7/06

10/1/0

6

9/25

/06

9/19

/06

9/13

/06

9/7/

06

9/1/06

8/25

/06

8/19

/06

8/13

/06

40

30

20

10

0

Buchanan UndredgedBuchanan Dredged

Average Daily Salinity in Buchanan Creeks

Date

Tur

bidi

ty (

NTU)

200

150

100

50

0

Buchanan UndredgedBuchanan Dredged

Average Daily Turbidity in Buchanan Creeks

Date

Dis

solv

ed O

xyge

n (m

g/L)

10/19/

06

10/13/

06

10/7

/06

10/1/0

6

9/25

/06

9/19

/06

9/13

/06

9/7/06

9/1/

06

8/25

/06

8/19

/06

8/13

/06

12

10

8

6

4

2

Buchanan UndredgedBuchanan Dredged

Average Daily Dissolved Oxygen in Buchanan Creeks

Tem

pera

ture

(C)

10/1

9/06

10/13/

06

10/7

/06

10/1

/06

9/25

/06

9/19

/06

9/13

/06

9/7/06

9/1/

06

8/25

/06

8/19

/06

8/13

/06

30.0

27.5

25.0

22.5

20.0

17.5

15.0

Buchanan UndredgedBuchanan Dredged

Average Temperature in Buchanan Creeks

Ernesto

Fish Survey Results5972 fish and

31 species collected

Other SppBlue Crab

MummichogSpot

Red DrumMullet spp

Atl. CroakerWhite PerchKillifish spp

Spotfin mojarraAmerican eelStriped bass

Summer flounder

Naked goby

The catches in the systems combined were dominated byAtl silverside, Bay anchovy, Gizzard shad, Silver perch, and

Atl. menhadenAverage sizes = 13.9 ± 4.6 cm (range 2.3—50 cm)

Blackcheek tonguefishBluefishPermitSheepshead minnowCrevalle jackHogchokerLadyfishSharptail gobySpotted seatroutTripletailWeakfish

The majority (72%) of the blue crabs captured were juveniles and many were

extremely small indicating that the Lynnhaven is used as a nursery ground.

26 adults were captured (11 female and 15 male).

Lynnhaven Tidal Creek Fish Community Similarity

Hebden_Undredged

Buch_Undredged

Hebden_Dredged

Buch_Dredged

North_Undredged

North_Dredged

1009080706050

Similarity

CreekCreek D/D/UU

Size Size (km(km2)2)

AbuAbu No. Spp = No. Spp = 99% 99%

NorthNorth UU 0.050.05 414414 1010

NorthNorth DD 0.090.09 294294 1010

HebdenHebden UU 0.60.6 10501050 1212

HebdenHebden DD 0.30.3 11171117 1010

BuchanaBuchanann

UU 4.94.9 968968 1010

BuchanaBuchanann

DD 0.60.6 21292129 88

General Community Characteristics among Creeks

Transform: Square rootResemblance: S17 Bray Curtis similarity

Location123

Similarity7075

N-U

N-D

H-U

H-D B-U

B-D

2D Stress: 0

Transform: Square rootResemblance: S17 Bray Curtis similarity

Spot

0.4

1.6

2.8

41

2

3

4

5

6

2D Stress: 0

Transform: Square rootResemblance: S17 Bray Curtis similarity

Red drum

0.3

1.2

2.1

3

N-U

N-D

H-U

H-D

B-U

B-D

2D Stress: 0

Species overlays

1) Spot more prominent

in the upriver systems Hebden and Buchanan

2) Red drum in higher abundance in

undredged systems vs. dredged systems

Fish Community Characteristics among Creeks

Variety of ways to describe communities:1) Abundance

2) Biomass3) Size

4) Diversity5) Fish community index

No Significant difference among sites surveyed (grouped by month) for Abundance

or Biomass

SIZE—NO difference among creeks or across months!!

Beach Seine

Gill Net

All Data

Diversity Among Creeks: NO significant difference!!

One-way ANOVA

Metrics were combined into an aggregate index--Fish

Community index (FCI)-- used to assess relative measures of fish community structure and function.

Fish Community Metrics

Species Richness/Diversity MeasuresSpecies Richness

Proportion of benthic-associated speciesNumber of dominant species (90% of total abundance)

Number of resident species

Fish Abundance Ln Abundance

Trophic CompositionTrophic Index

Nursery FunctionNumber of estuarine spawning speciesNumber of estuarine nursery species

Fish Community Index (FCI)

Fish Community Index comparison among creeks

NO difference!

Preliminary Conclusions All six creeks supported similar fish communities

Slight differences among fish communities (seen in multivariate analyses) may be related to the size of the watershed (i.e. North creeks differed)

Extreme variability in physical and chemical features in the Lynnhaven are driving influences to structuring fish communities

Diverse communities in Lynnhaven (related to its location at the Bay mouth) utilize the Bay as feeding/nursery grounds

The most recently dredged system was similar to the adjacent undredged system (North creeks) which may indicate a quick recovery rate for fish communities post-dredging

HOWEVER, presence of fish does not mean no impact occurs from dredging, information on prey communities is necessary, as well as long term studies to estimate impacts.

Three-tiered shoreline assessment approach, dividing the shorezone into three regions

1) the immediate riparian zone, evaluated for land use;

2) the bank, evaluated for height, stability, cover and natural protection; and

3) the shoreline, describing the presence of shoreline structures for shore protection and recreational purposes.

Shoreline Continuous Inventory: Lynnhaven Bay

Dix Creek

Example survey map of Shoreline

structures in Lynnhaven Bay

Preliminary Results: Total Survey Miles:  139.42 Coded Miles:  107.46 Marsh Islands Miles: ~ 17.69

Line structures for the coded shl:  26.12 miles

So far we estimate ~30% of coded shoreline is hardened

TMI (from 1970s): 1157.1 acres

Webpage for Shoreline Inventory Data, Maps and Reports

http://ccrm.vims.edu/shoreline_inventories/virginia/lynnhaven/

lynnhaven_disclaimer.html