Assessing Linkages between Nearshore Habitat and Estuarine Fish Communities in the

Chesapeake Bay 

Donna Marie Bilkovic*, Carl H. Hershner, Kirk J. Havens,Marcia R. Berman, David Stanhope and Lyle Varnell

 

Center for Coastal Resources ManagementVirginia Institute of Marine Science

Atlantic Slope Consortium (ASC)

ASC

Estuarine Indicator Research Programs in the United States

Research Institutes involved include: Pennsylvania State, Smithsonian Environmental Research Center, East Carolina University and Virginia Institute of Marine Science

“Our suite of indicators will produce integrated assessments of the condition, health and sustainability

of aquatic ecosystems based on ecological and socioeconomic information compiled at the scale of estuarine segments and small watersheds, with clear

linkages and connections to larger scales”.

Brooks et.al., 2001

Stated GOAL of the Atlantic Slope Consortium

website: www.asc.psu.edu

Can nearshore habitat be linked with fish community integrity, and are these accurate indicators of aquatic

ecosystem health?

Study Objectives

Develop and test fish community metrics that assess the

health of shallow-water estuarine systems in the Mid-Atlantic

Assess relationships among shoreline condition, subtidal

habitat, and fish community metrics

Assess potential relationship between watershed land use and

shallow-water estuarine fish communities*.

* Relationship between watershed land use and riparian land use observed for agricultural, forested and developed landscapes

Comparison between percentages of each land use type in a watershed, and the corresponding riparian land use category: A) developed, B) agricultural, or C) forested. Data were extracted from a subset of thirteen watersheds in the Chesapeake Bay.

Developed Watershed Land Use (%)0 20 40 60 80

Dev

elop

ed S

hore

line

L

and

Use

(%

)

0

10

20

30

40

50

60

70

80 r = 0.54; p =0.05

Agricultural Watershed Land Use (%)0 10 20 30 40 50

Agr

icul

tura

l Sho

reli

ne

Lan

d U

se (

%)

0

10

20

30r = 0.58; p =0.039

Forested Watershed Land Use (%)10 20 30 40 50 60 70 80

For

este

d S

hore

line

L

and

Use

(%

)

0

20

40

60

80

100r = 0.65; p = 0.017

Sampling Locations and Watershed Land Use on the Chesapeake Bay

166,000 km2 watershed18,804 km of shoreline320 km long5.5 to 56 km wideonly 6.5 m average depth15 million people live in basin

Watershed Selection

25 Watersheds selectedSalinity regime =

oligo-mesohalineAt least three watersheds in each land use class were sampledLand use categories

1) forested 2) agricultural

3) developed

Selection Criteria

5 SITES per watershed were sampled…

At each SITE we assessedHabitat Condition

Shoreline (alteration)Subtidal (physical structure)

Biotic CommunitiesFishPrey species

Water chemistry/physical

Habitat Assessments

Shoreline Alteration

Artificial shoreline/embankments or dams or bridge abutments absent or minimal; stream with meandering pattern

Some artificial shoreline/embankments present (<40% of shoreline onsite); no evidence of recent shoreline alteration activity

Artificial shoreline/embankments present at some extent (40 to 80% of stream site altered), evidence of recent shoreline alteration activity

Artificial shoreline/banks (over 80% of the stream site disrupted), evidence of recent shoreline alteration activity

Score 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Optimal Suboptimal Marginal Poor

Eight metrics were assessed for consistency as indicators of aquatic ecosystem health based on fish community structure and function.

Fish Community Metrics

Fish Community Metrics Reference

Species Richness/Diversity MeasuresSpecies Richness this paperProportion of benthic-associated species Deegan et al. 1997Number of dominant species (90% of total abundance) Deegan et al. 1997Number of resident species Deegan et al. 1997

Fish Abundance Ln Abundance Deegan et al. 1997

Trophic CompositionTrophic Index Jordan and Vaas 2000

Nursery FunctionNumber of estuarine spawning species Deegan et al. 1997Number of estuarine nursery species Deegan et al. 1997

Statistical Analyses

• Assessment of applicability and consistency of metrics

• Comparison among Fish Community Index scores, shoreline condition and subtidal habitat measures

• Comparison of Fish Community Index with overall watershed land use patterns

Fish Community Metrics Assessment

Metrics were combined into an aggregate index by summing standardized individual metric values.

All but one of the examined fish community metrics was positively and highly correlated (r>0.5) with the summed metrics. Total abundance was excluded from the final fish community index (FCI).

Species Richness

0 2 4 6 8

FC

I

1

2

3

4

5

6

7r = 0.83; p < 0.0001

Proportion of benthic-associated species

0.0 0.2 0.4 0.6 0.8 1.0

FCI

1

2

3

4

5

6

7r = 0.54; p < 0.0001

Number of Dominant Species

0 1 2 3 4 5 6 7 8 9 10

FCI

1

2

3

4

5

6

7r = 0.74; p < 0.0001

Number of Resident Species

0 2 4 6 8 10 12

FCI

1

2

3

4

5

6

7r = 0.87; p < 0.0001

All Significant positive relationships

Number of Estuarine Nursery Species

2 4 6 8 10 12 14 16

FCI

0

1

2

3

4

5

6

7r = 0.88; p < 0.0001

Trophic Index

0 1 2 3 4 5

FC

I

1

2

3

4

5

6

7r = 0.66; p < 0.0001

Ln Abundance

2 3 4 5 6 7 8 9

FC

I

0

1

2

3

4

5

6

7

8r = 0.16; p = 0.09

Number of Estuarine Spawning Species

2 4 6 8 10

FC

I

1

2

3

4

5

6

7r = 0.82; p < 0.0001

Except…

PC1 PC2 Variable0.44 0.14 Species Richness0.23 0.38 Proportion of benthic-associated species0.38 0.27 No. of Dominant Species0.41 0.27 No. of Resident Species0.02 0.67 Ln Total Abundance0.35 0.30 Trophic Index0.38 0.33 No. of Estuarine Spawning Species0.43 0.24 No. of Estuarine Nursery Species57 23 % Variance accounted for

Additionally, we examined the metrics using PCA…

which indicated that the use of all the metrics, with the exception of total abundance, is supported for the development of a multi-metric FCI of the nearshore in coastal plain estuarine ecosystems.

Fish Community Metrics Assessment

Metrics were combined into an aggregate index by summing standardized individual metric values.

All but one of the examined fish community metrics was positively and highly correlated (r>0.5) with the summed metrics. Total abundance was excluded from the final fish community index (FCI).

Do Fish Respond to Variations in Nearshore Condition?

Fish Community and Habitat Comparisons

Available subtidal habitat

Low Moderate Abundant

Fis

h C

omm

unit

y In

dex

(FC

I)

0

1

2

3

4

5

6

7 p<0.001; all different

FCI scores were significantly different among all subtidal habitat categories. Higher scores were associated with increasing abundance of subtidal habitat

Amount of Alterations to Shoreline

High Moderate Minimal

Fis

h C

omm

unit

y In

dex

(FC

I)

0

1

2

3

4

5

6

7 p=0.003; High vs.Minimal

FCI scores were significantly lower at sites with highly altered shorelines versus minimally altered shorelines.

Watershed Land Use Category

Developed Agriculture Forest

Fis

h C

omm

un

ity

Ind

ex (

FC

I)

0

1

2

3

4

5

6

7

Watershed Land Use versus Fish

FCI scores were significantly lower in developed and agricultural watersheds versus forested watersheds.

p=0.03

Subtidal Habitat related to Shoreline Condition

Shoreline Condition (altered--unaltered)

0 5 10 15 20

Sub

tidal

Hab

itat (

none

--ab

unda

nt)

0

2

4

6

8

10

12

14

16

18

20

22

r = 0.575; p < 0.0001

Increased shoreline condition was associated with increased availableSubtidal structure (shelter for fish).

Habitat Comparisons

Developed

ForestedAgricultural

Highly Altered

UnalteredModerately Altered

Minimal Habitat

Abundant HabitatModerate Habitat

Seven of eight tested Fish Community Metrics were included in a

final index, and may be useful indicators of biotic integrity in shallow

water estuarine systems.

Linkages could be discerned between FCI scores and not only local

habitat influences, but also on a larger watershed scale. Thus, HABITAT

CONDITON shows promise as an indicator of estuarine health.

Linkages existed among habitat at various scales (e.g. Decreases in

FCI scores were evident with developed watersheds and shorelines which

were subsequently linked with the loss of subtidal habitat structure)

Future management tools?

Summary

Ongoing continuous shoreline surveys extract information on shoreline condition (land use,structures, bank condition etc.) for comparison with biotic communities

GPS ContinuousSurvey

Assessment of shorelinecondition impacts on fish communities at multiple spatial scales

Acoustic habitat mapping in the nearshore and comparison of specific habitats with biota

Explore temporal trends in fish communities indices

Examine additional biological communities in association with shoreline condition (e.g. benthic macroinvertebrates).http://ccrm.vims.edu/gis/gisdata.html

Future Research

For instance…a metric measuring benthic community health increased as shoreline and watershed land use exhibited more natural conditions

W-value in relation to watershed and shoreline land use

Ben

thic

Com

mun

ity

Met

ric

(W-v

alue

)(d

istu

rbed

......

......

......

......

......

......

......

undi

stur

bed)

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

AG/Dev AG/Ag AG/For FOR/For

Land use/ Shoreline

Thanks to:Colleagues at SERC, Penn State, ECU and VIMS; funding source: Environmental Protection Agency, STAR Program