After nearly 100 years of absence the Tees is now once again home to native oysters. On the 28th of September we marked the completion of the first stage of our attempt to reintroduce these coastal heroes. With the help of our wonderful volunteers, we installed 20 Oyster nurseries and a total of 638 oysters into Hartlepool Marina. Each nursery consists of a flexible inner cage with 27 separate compartments for holding oysters and a stronger outer cage to protect the oysters from predators. Oysters were delivered from Scotland and scrubbed to remove any potential invasive species before being placed into the marina. Now in they're new home the oyster will start to filter seawater and increase biodiversity in the area.
Native Oyster Biology
Unlike most other oysters which release unfertilised eggs and sperm into the water column, female native oysters hold their eggs within their shell cavity for fertilisation to occur. These eggs then develop into microscopic baby oysters known as larvae, which are then released into the water column after 8 to 10 days. Each female can release over 1 million larvae a year into the ocean. These larvae then have roughly 2 weeks to find a pace to settle and change into immobile spat. Oysters are gregarious meaning they live in clusters. Because of this the preferred settlement for oyster larvae is other oysters, failing this they will settle on any shells or other hard surface. Unfortunately this sort of habitat is lacking from the Tees estuary; an issue that will be the focus of the next phase of our restoration project.
What's next?
Now we have native oysters living happily in our oyster nurseries it is important to monitor how they are getting along. Every month we will be taking the cages out of the water to check how many of the oysters have died. The nurseries will also be an excellent habitat for crustaceans and fish we will be counting the number of different species living within our oyster nurseries. The next phase of our project will be making sure that the tens of millions of larvae released each year have somewhere nice to settle and call home. We will be placing large amounts of gravel and scallop shells (oyster shells are hard to come by) in the sea around the marina. We will trial spawning oysters in large tanks with shell in the tank. This will increase the likelihood of oysters settling on to the shells which can then be placed out into the estuary to grow into adult oysters
As well our volunteers we'd like to thank Hartlepool Marina for their help and continued support for this project. If you would like to get involved with any of our Native oyster monitoring or would just like more information on the project please email our project officer Henry (henry@teesriverstrust.org)