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Oyster Reefs Food Filters Fish Habitat Breakwaters

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Presentation on theme: "Oyster Reefs Food Filters Fish Habitat Breakwaters"— Presentation transcript:

1 Oyster Reefs Food Filters Fish Habitat Breakwaters
Oysters have been harvested for human consumption since time immemorial. Certainly the Indians were fond of them, as attested by oyster middens along the coast. Oysters are also food for birds, crabs, otters, raccoons, etc. But they are more than food.

2 Oysters as Filters A single adult oyster can filter 2.5 gallons water per hour Controls phytoplankton Removes silt Improves water quality Nutrient transfer Oysters are amazing filterers. A single oyster filters 2.5 gallons an hour or 50 gallons of water a day. To put that in perspective, it is said that at one time the oysters in the Chesapeake Bay could filter all the water in the bay in a couple of days. Unfortunately, the oyster populations there have been reduced to the point that now it takes more than a year for the existing oysters to filter the Bay. In the filtering process, oysters control phytoplankton blooms, remove silt, improve water clarity and improve overall water quality. In colonial times it is said that you could see a ships anchor on the bottom of the Chesapeake, now visibility is no more than 18 inches.

3 Intertidal Oysters Create Habitat
Spottailed bass Gray snapper Southern flounder Summer flounder Spot Sheepshead Darter goby Naked goby Striped blenny Striped mullet White mullet Oyster toadfish Bay anchovy Striped anchovy Mummichog Atlantic silverside Inland silverside Spotfin mojarra Pinfish Silver perch Pigfish Speckled worm eel Chain pipefish Marsh grass shrimp Daggerblade grass shrimp Brown shrimp White shrimp Blue crab Lesser blue crab When the tide covers the reef, many other fish and crustaceans can be found.In this partial listing you can see important recreational species such as sheepshead, flounder and spottailed bass.

4 Oysters are a keystone species

5 Oysters as natural breakwaters
Protect saltmarsh Reduce bank erosion Trap silt Reduce wave energy In South Carolina, where 95 % of our oysters occur intertidally, oysters also function as natural breakwaters which protect the adjacent saltmarsh from erosion by waves and boatwakes.

6 Results of recent research in SC
Intertidal oyster banks provide natural ‘bulkheads’ in salt marsh fringed creeks Boat wakes are a factor in shoreline erosion (including oyster reefs and saltmarsh habitats) Intertidal oysters are frequently restricted by a lack of suitable hard substrate for attachment Oysters readily recruit to shell placed in appropriate areas Even newly planted shell attracts more species than mudflats Fully functional reef requires >3 years to develop

7 Reduction of Natural Oyster Habitat
Over-harvesting Removal of habitat Physical disturbance Diseases Reduced water quality Alteration of flow and salinity Predators and competitors What has caused these declines? Some factors are listed here. Overharvesting has unquestionably been a factor in the Chesapeake. The harvesting process destroys and removes the habitat needed for new recruitment. Oyster reefs are also impacted by physical disturbances such as waves and boat wakes. Disease has been the final straw in the Chesapeake and now in North Carolina. Reduced water quality as a result of increased coastal development weakens oysters and makes them more susceptible to disease and natural stressors.

8 Where did all the reefs and shell go?
Overharvesting One year’s shell from a single Chesapeake Bay shucking house

9 So, I hope I have convinced you that oysters are important
So, I hope I have convinced you that oysters are important. Now let’s move on to “What’s the problem? Why do we need to take action?” To understand the problem we have to look at the life cycle of the oyster. Adult oysters spawn during the summer months. Because fertilization occurs in the water column, it is important for oysters to live in close proximity to each other, maximizing the likelihood of sperm meeting egg. Within 24 hours a free-swimming larva is formed. This veliger larva drifts with the currents for up to 3 weeks, possibly travelling far from where it was spawned. At the end of this 3 week larval period, young oysters settle to the bottom and attach to a hard substrate. Not unexpectedly they have evolved to prefer setting on oyster shell. In fact chemicals from adult oysters attract larvae, helping them to home in on a suitable settling spot. Thus oyster beds do not readily form in new locations. Instead, oyster reefs expand vertically and horizontally as new recruits attach to older residents. Unlike fish, crabs and even clams, adult oysters are unable to move. They cannot escape from harvesters or hide to avoid a boat wake.

10 Oyster Habitat Restoration
Oyster habitats can be restored and enhanced by planting of oyster shell Juvenile oysters will cement to the shell in the summer months and eventually form a new reef Shell is in short supply so DNR is encouraging shell recycling

11 SCORE Community-Based Oyster Restoration Program
Augments state workforce Volunteers work with scientists to build oyster habitat monitor water quality and reef progress Constructed habitats serve as research platforms to improve restoration success Volunteers gain a vested interest in oyster habitats

12 Volunteer Roles Site Selection Shell Recycling Shell Bagging
Reef Building Post-construction monitoring Water quality Reef progress Field trips Local area contact - volunteer coordinator

13 Site Selection Oysters naturally occurring in general area or evidence of oyster habitat in past Firm bottom Gentle slope Salinity, flow conducive to oyster growth Siltation/erosion factors Accessibility Reef construction/monitoring School activities Exposure to boat wakes/wind-generated waves Contaminants Potential for human disturbance Step 2 is to decide where to put the shell. Since we have a limited supply of shell we want to maximize its efficacy by choosing sites where success is likely. Some of our criteria include...We will be asking knowledgeable locals for suggestions on reef location.

14 Shell Recycling Environmental Action volunteers recycle about 1000 bushels each year! For assistance call: (843) For locations and maps:

15 Shell Bagging More than 15,000 bags in 4 years!

16 Reef Building 98 reefs at 28 sites since 2001!

17 Reef at Palmetto Islands County Park
3 months after construction

18 South Carolina Oyster Restoration and Enhancement Sites
Murrell’s Inlet Huntington Beach State Park Pawley’s Island McClellanville Cape Romain Palmetto County Park Boone Hall Kiawah Rockville Fort Johnson Riverland Terrace Alberta Long SC Aquarium Patriots Point Boy Scout Camp Beaufort Marine Institute Edisto Dataw Chowan Creek Port Royal Callawassie Waddell Mariculture Center Trask Boat Landing Pinckney Refuge Pinckney Landing Sites Constructed South Carolina Oyster Restoration and Enhancement Sites 28 sites 98 reefs >250 tons shell


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