Tilghman Islanders Grow Oysters mid-year update



Our oyster restoration program, Tilghman Islanders Grow Oysters, is officially halfway through the growing season!


In September, we placed over 100 cages of oyster spat on shell with volunteer growers throughout the Bay Hundred area. A few volunteers agreed to go above and beyond and have been measuring their oysters once a month so that we can keep track of how the oysters are doing.


At the start of the program, the oyster spat were an average of 17.9 mm (which is 0.7 inches). As of our January data collection, the oysters have grown an average of 15.8 mm, reaching an average size of 33.7 mm (1.3 inches). This means the oysters have almost doubled in size in 4 months!


NOAA Buoy locations


Most of this growth occurred early on, with the oysters growing an average of 10 mm from September to October. As water temperatures cooled, the growth of the oysters slowed, with very little growth occurring between November and January.


Based on the current water temperature of 37o F at Gooses Reef, we will likely see low growth for February as well. This data comes from one of several water quality buoys in the Chesapeake Bay which are managed by the National Oceanic and Atmospheric Administration.


As spring finally arrives and air temperatures begin to increase, water temperature will also slowly increase so we should see more growth when we measure our oysters in March.


By the time we collect the oysters at the end of the program, these oysters should be even larger. Last year, cages were collected a little later than normal due to scheduling issues caused by the COVID-19 pandemic. This meant the oysters had more time to grow during warmer months and the average oyster was 53.5 mm (2.1 inches). We don’t expect to see oysters of quite that size this year, but we should see an average of 40 mm and may even see an average of above 45 mm.


The reason this is exciting is because smaller oysters are more vulnerable to predation. Oyster shells are relatively thin when they are small. As it grows, an oyster puts more layers of shell down, making the shell thicker. The more the oysters are able to grow while they are relatively protected from predators in our TIGO cages, the more likely they are to survive when we plant them on wild reefs.


In addition, the often quoted feat of an oyster being able to filter 50 gallons of water a day is only for adult oysters. Smaller, juvenile oysters filter significantly less water, so the larger the oysters, the more water they are able to filter. One of the main purposes of working to restore oyster populations is to increase the health of the Chesapeake Bay, so the more oysters we produce and the larger those oysters are, the more water they filter.


All in all, we are very pleased with how well the oysters are doing so far and we expect to see continued growth as we move into spring. Stay tuned for future updates on our TIGO program and this year’s oysters!