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Partnership Helps Oyster Populations Recover - October 2, 2016

                Whether you enjoy them raw, on the half shell, Rockefeller, fried or frittered, oysters are a staple here in Maryland. And while they are certainly delicious, oysters do much more for us than just provide food.

                Oysters are a keystone species in Maryland’s bays; a species of great importance to the overall health of the ecosystem. These enigmatic bivalves have a relatively simple life; however, they play a major role in keeping our water clean and our wildlife healthy.

                Oysters start life as a veliger, a mobile juvenile stage in their lifecycle. Eventually the veliger will settle down, preferably on old oyster shells, and begin to grow. Due to their propensity to grow on old oyster shells, oyster reefs are common occurrences, although they are much smaller and fewer in number today compared to historic averages. Things like over harvesting, increased disease, falling salinity due to runoff that accompanies increased impervious surfaces, increased sedimentation from runoff, and poor water quality all contribute to the loss of oysters in our bays. Current estimates put upwards of 90% of our historic oyster reef habitat as lost and the current population of oysters in the Chesapeake Bay is less than 1% of the levels it once was.

                Oysters, along with most other bivalves, are filter feeders. This means that in order to feed, the oyster has to suck water in, filter it over their gills, and then expel it into the water column. Oysters have evolved to be incredibly efficient filter feeders and can filter nearly 50 gallons of water a day! Collectively, the oyster population of the Chesapeake Bay used to filter all the bay water within about a week, however due to a decrease in population and stress on the oysters, it takes about a year for the same volume of water to be filtered.

                Not only do oysters help to filter and clean our water columns, they also help to provide some much needed habitat. Habitat on the bottom of our bays is at a premium; with Submerged Aquatic Vegetation (SAVs) disappearing and oyster reefs shrinking there is less and less preferred benthic habitat available. This means that the habitat provided by our remaining oyster reefs is crucial to the survival of some of our bay animals, like blennies, crabs, snails, juvenile fish, and shrimp. Without the oyster reefs and SAV beds, these smaller critters would have nowhere to feed or hide from predators.

                Despite their rugged appearance and hard outer shells, oysters are vulnerable to a number of diseases, predators, and problems. Depending on the life stage, different predators can target the oysters. Oyster larvae are mainly preyed upon by other filter feeders, especially comb jellies in the bays. Once they reach their adult form, they are mostly preyed upon by cownose ray, black drum, oyster drills, crabs, worms, and even boring sponges.

                Two of the biggest threats to oysters in our bays are the diseases MSX and Dermo.  Dermo, which is caused by the parasite, Perkinsus marinus, was first recorded in the Chesapeake Bay in 1949 and is more prevalent in lower-salinity waters. Meanwhile MSX, which is caused by Haplosporidium nelsoni, was first found in the Chesapeake Bay in 1959, about a decade after we found Dermo in the Bay. MSX tends to be more common in higher-salinity waters like the Coastal Bays and the mouth of the Chesapeake Bay. Both of these diseases result in extremely high mortality rates, often killing upwards of 80-90% of infected oysters. These diseases have resulted in the deaths of countless oysters and have negatively impacted harvesting.

                In order to help combat the loss of oysters due to the plethora of problems facing them, many different organizations and individuals are partnering together to help restore these keystone species. One program doing a lot of great work in restoring oyster populations is the Marylanders Grow Oysters (MGO) program.

                The MGO is managed by the Maryland Department of Natural Resources in conjunction with the Oyster Recovery Partnership. The MGO was initiated in 2008 by Governor O’Malley and has grown in size and popularity each subsequent year. The program is set up so homeowners can grow young oysters in pre-made cages off their docks and jetties before the oysters are re-collected and re-distributed onto oyster sanctuary zones. The oyster sanctuaries are areas in need of major restoration, so these areas are specifically targeted for oyster replenishment and are off limits for commercial and recreational oyster harvesting.

                When the program started in 2008, it had only 850 cages in its first year; however, it now has over 7,500 cages tended by 1,500 MGO volunteers throughout Maryland’s waterways, including here in the Coastal Bays. Last year alone, the MGO program grew over 2 million young oysters to distribute onto oyster sanctuaries, helping to replenish the quickly dwindling native population.

                If you are interested in the MGO program or volunteering to help grow oysters on your docks or jetties, the Maryland Coastal Bays Program can help! Please contact our Watershed Program Coordinator, Amanda Poskaitis at amandap@mdcoastalbays.org or call at 410-213-2297 ext. 103 to find out more information or help volunteer.

 

Jackson is the former Education Coordinator for Maryland Coastal Bays Program and current graduate student at Clemson University. 

 



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