Matthew W. JohnsonS. Powers, J. Senne, K. Park

ICSR 2008Charleston, SC

21 November 2008

Oyster Reefs

Exploitable fishery and an essential habitat for many other species.

Destructive fishing practices remove not only harvestable oysters, but the complicated reef matrix future generation of oysters require.

Oyster “tonging”

Hydraulic dredges

Cedar Point/Dauphin Island1407 hectares

WhitehouseReef

Point Clear Reefs

Fish River/Shell Bank

Photos Courtesy of Mississippi Department of Marine Resources

Settlement &

Growth

Physical and Biological Challenges

Healthy Oyster Reef

After Katrina

Before Katrina August 2007

Dissolved Oxygen

Larval supply

20 0 10 0 10 5

2

1

# spat m-2 d-1

(Hoese et al. 1972)

Predation

2.5 m

1 m

2 m

Anoxic

Hypoxic

Normoxic

1. Stop the reason for hypoxia

2. Build out of the hypoxia

Relic Reef

Mud Bottom

ADCNR “Reef Donut”

Determine extent of hypoxia in this area.

Ensure that adequate larval settlement to area.

Measure oyster spat survival and growth to see how this related to depthShort-cut to reef design

A priori designation of 3 different oxygen regimes

Similar larvae supply

Similar Depth, 2.75-3 m

Control predation

Extreme Hypoxia

Moderate Hypoxia

No Hypoxia

200

100

10 5

2

1

0.5 X 0.5 m

5 X 5 or 4 X 6

79 ± 19 (SD) spat

3 replicates per location

Oysters deployed on 7/11/2007 and checked biweekly until 9/6/2007, 10/9/2007

Oyster were cleaned of epibionts and counted

Measured at final date

0.5 m

1.25 m

Mesh size 1 cm2

YSI deployed at each depth at each location

June 29- Aug 27 (5X), Sept 24, Oct 17 Measured DO at 19 stations near Whitehouse Reef

Dissolved Oxygen

Bottom

1.3 M Off Bottom @Whitehous

eReef

Anoxia Hypoxia Normoxia

June 29 July 5 July 19 August 14 August 27

Location- p<0.001Depth- NSTime- p<0.001Time x Location p<0.001

Repeated Measures ANOVA

X Data

-0.04

-0.02

0.00

0.02

0.04

Theodore Industrial Canal

-0.04

-0.02

0.00

0.02

0.04

0.06

Whitehouse Reef

Sample Date

7/23/2007

7/30/2007

8/6/2007

8/13/2007

8/20/2007

8/27/2007

9/3/2007

9/10/2007

9/17/2007

9/24/2007

10/1/2007

10/8/2007

Inst

ane

ous

Pop

ulat

ion

Gro

wth

(%

indi

vidu

als*

day

-1)

-0.05

0.00

0.05

0.10

0.15

0.20

Surface1.0 m above bottom0.1 m above bottom

Dauphin Island

Theodore Industrial

Canal

Whitehouse Reef

Dauphin Island

Depth

Surface 1.0 m 0.1 m

Inst

anta

neou

s P

opul

atio

n G

row

th (

% in

divi

dual

s*da

y-1)

0.00

0.02

0.04

0.06

Whitehouse ReefDauphin IslandTheodore Industrial Canal

2-way ANOVALocation x Depth- p<0.001

K-W ANOVA on Ranks Location- p<0.001Depth- p<0.001A B C

AB

C

AB

C

A

B

C

2-way ANOVALocation x Depth- p<0.001

K-W ANOVA on RanksLocation- p<0.001Depth- p<0.001A B C

AB

C

AB

C

A

B

C

0.5 m

1.25 m> 1.0 m

Practical Applications……

Settlement at all depths and all locations Dissolved oxygen did influence

population growth, individual growth Response under moderate hypoxia

similar to that of severe hypoxia

Funding University of South Alabama Oyster

Restoration Project NOAA/NMFS

Personnel Crystal Hightower Matt Kenworthy Jason Herrmann Stan Bosarge Multiple Interns

Decreased long-term production Stabilized production in recent past

Cedar Point

Date

1/1/2005

7/1/2005

1/1/2006

7/1/2006

1/1/2007

7/1/2007

1/1/2008

7/1/2008Oys

ter

Abu

ndan

ce (

Log

(abu

ndan

ce+

1)

* 0.

5m2 )

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

Adults High ReliefSpat High ReliefAdults Low ReliefSpat Low Relief

2005-2008Population in trouble?