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Matthew W. Johnson S. Powers, J. Senne, K. Park ICSR 2008 Charleston, SC 21 November 2008
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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
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Cedar Point/Dauphin Island 1407 hectares Whitehouse Reef Point Clear Reefs Fish River/Shell Bank
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Sub-tidal Reefs Unconsolidated Thin veneer Put and Take Fishery Low relief Good for tonging Photos Courtesy of Mississippi Department of Marine Resources
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Settlement & Growth Physical and Biological Challenges Healthy Oyster Reef
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After Katrina Before Katrina August 2007
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Dissolved Oxygen Larval supply 20010010 5 2 1 # spat m -2 d -1 (Hoese et al. 1972) Predation
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2.5 m 1 m 2 m Anoxic Hypoxic Normoxic 1. Stop the reason for hypoxia 2. Build out of the hypoxia
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Relic Reef Mud Bottom ADCNR “Reef Donut”
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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 depth Short-cut to reef design
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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 20010010 5 2 1
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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 cm 2
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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
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Bottom 1.3 M Off Bottom @ Whitehouse Reef
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AnoxiaHypoxiaNormoxia June 29July 5July 19 August 14August 27
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Location- p<0.001 Depth- NS Time- p<0.001 Time x Location p<0.001 Repeated Measures ANOVA
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Theodore Industrial Canal Whitehouse Reef Dauphin Island
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2-way ANOVA Location x Depth- p<0.001 K-W ANOVA on Ranks Location- p<0.001 Depth- p<0.001 ABC A B C A B C A B C 2-way ANOVA Location x Depth- p<0.001 K-W ANOVA on Ranks Location- p<0.001 Depth- p<0.001 ABC A B C A B C A B C
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0.5 m 1.25 m > 1.0 m Practical Applications……
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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
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Funding University of South Alabama Oyster Restoration Project NOAA/NMFS Personnel Crystal Hightower Matt Kenworthy Jason Herrmann Stan Bosarge Multiple Interns
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Decreased long-term production Stabilized production in recent past
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2005-2008 Population in trouble?
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