Picky Oysters

The release of our latest Oyster Habitat Suitability report and an Artificial Reef project on the horizon.

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Louisiana oysters have a Goldilocks complex. They need a not-too-fresh and not-too-salty environment to survive long enough to make it onto our plates.

 

That perfect balance can be hard to find on a changing coast. Since the early days of oyster dredging, the location of historic oyster populations has been shifting. Some are worried that it might disappear altogether when coastal restoration plans reconnect the Mississippi River to the area. But there is good news: This past week, the Lake Pontchartrain Basin Foundation (LPBF) released a report identifying areas where the water might be "just right" for oyster now and in the future.

 

The foundation will be putting their report findings into action by installing four artificial reefs as part of a Louisiana Department of Wildlife and Fisheries (LDWF) program. Although the reefs are intended to provide habitat for fish, LPBF thinks they will also support oysters. The reefs will be located in the Biloxi Marsh and the Mississippi Sound, areas identified in the report as suitable for oyster reproduction.

Oyster Habitat Suitability Study Area Map
Oyster Habitat Suitability Study Area Map

The Biloxi Marsh is located 40 miles east of New Orleans and north of the Mississippi River Gulf Outlet (MRGO), which was closed in 2009. Prior to its closure, the MRGO greatly influenced the area. It shortened the distance between inland marshes and the Gulf, causing salinity in the region to rise. Since the canal's closure, the area has generally recovered. It seems likely that oysters will survive in the area, as they did before the construction of the MRGO.

Artificial reefs provide more productive fish habitat while enhancing recreational fishing. These ‘islands’ of relief on the otherwise flat, soft lake bottom attract and support a wide variety of life. They disrupt water currents and provide critical hard structure, which makes a better habitat for bottom-dwelling organisms and acts as a small speedbump slowing storm surge. These invertebrates form the base of the food web and support large species including sport fish. If these reefs are placed in an area that is "just right," oyster spat may settle and turn the reef it a thriving oyster habitat.

Artificial reefs are simple: they provide a hard, dynamic substrate needed for oysters to attach to and grow. Two common materials used are reef balls* and cultch- broken up concrete and shells. *LPBF was the first to use these in Lousiana in 2003.

Twice a year in the Gulf of Mexico a single oyster can release up to 100 million eggs. After an egg is fertilized, it becomes a free-swimming larva able to travel and establish itself on a neighboring reef. That means that during the oyster spawning season, there are many, many larvae and that they can populate new areas uninhabited by their predecessors.

Although the oysters that will grow there will be off-limits for dredging, the artificial reefs will be expected to help boost oyster populations in nearby areas, where oysters can be harvested.

The coastal oyster stock has been below the long-term average every year since 2007, and the stock has been decreasing since 2014. LPBF's artificial program expects to maintain an oyster population, even if the commercial stock continues to dwindle. With this reserve, a supply of larvae will remain- ready to use to restore the population.

It's important that Louisiana maintain an oyster population, for coastal ecology and resiliency. The hard substrate of oyster reefs is an important feature of the coast, helping it to guard against storm surge. Similar to barrier islands, oyster reefs act as a speed bump slowing and absorbing wave energy.

 

LPBF scientists have been studying oyster habitats in Louisiana for almost a decade, partnering with other leading scientists Drs. Porrier and Soniat. Their study considers salinity, historic oyster reefs, nearby oil and gas activity, and oyster dredging hotspots- where commercial oystermen congregate for harvesting. You can read it here.

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