It is that time of year again when we say goodbye to native oysters until the end of September. After all, it is these oysters that the 'R' in the month saying refers to.
Why do we stop dredging native oysters in the summer?
The native oyster is both male and female and changes from one to the other during the warmer months. When the oyster spatting season approaches, which is now, the oyster is male and discharges seed into the water where it floats about until it gets drawn back into the oyster. Oysters are filter feeders and get their nutrients from the water, it's through this same process that the seed comes back into the oyster where it meets the eggs which are attached to the gills.
When the eggs are first seen attached to the gills they are white and are said to be 'white sick' and this is when we stop dredging the oysters. This doesn't happen at the same time every year, it depends greatly on the temperature of the water. Oysters can spat more than once during the summer, which is why we leave them alone so they can breed and nature can restock our oyster beds.
What happens to the baby oysters - the oyster spat?
After a time, inside the oyster, these eggs grow and ripen getting their shells formed and hardened and are said to be 'black sick'. Once the little oysters are ready the oyster discharges the spat into the water, much like a puff of smoke.
The little oysters, called spat, then float about until they find something hard on the seabed to fix onto where they will lay for the next five years until they are ready to dredge. To encourage the spat to settle where we can find them, we lay crushed cockle and oyster shells on to our oyster beds to give the spat something to grab hold of as our beds are mostly made up of a solid black mud.
It's not an easy life for the small oyster spat, any cold snaps can kill off the oyster spat, plus they are a favourite food for crabs and starfish, both which reside in our river. It is a good job that each oyster discharges over a million of these tiny oysters each time they spat.