I wasn’t prepared for what awaited me as I stepped off the boat. “It’s shocking, isn’t it?” remarked Matt Slater, marine awareness officer for Cornwall Wildlife Trust. Shocking perhaps, but the real surprise is that, with a little creativity and entrepreneurial spirit, this latest environmental threat could have a happy ending and be an exciting new business opportunity to boot!

Matt and I, together with the Springwatch film crew, had travelled to a small beach across from Fowey Harbour to cover a story of an alien invasion. On its own, the culprit looks benign enough: the Pacific oyster was introduced here in 1929 and then later in the 1960s in oyster farms. Originally native to Japan’s Pacific coast, it has been used around the world for its supersized-style life history. Compared to the native flat oyster, Pacific oysters grow fast and breed young, making them ideal for aquaculture. The received wisdom was that UK waters were too cold for this non-native to ever establish itself successfully in Britain. Unfortunately, things have changed.

Photograph by Charles Francis

A recent succession of mild winters and warm summers has tipped the balance. Over the past six years, an explosion of Pacific oyster numbers has been witnessed in Cornwall and South Devon. A two-year project, funded by the European Marine and Fisheries and led by Natural England in partnership with Cornwall Wildlife Trust’s Shoresearch Project and South Devon AONB Estuaries Partnership, is mobilising teams of citizen science volunteers who are going out and recording oyster populations. Surprisingly, they are being found all around our coasts, in open bays as well as estuaries. The densest populations in Cornwall are in the Fal, Helford, Fowey, Looe, Par, Whitsand Bay, Mounts Bay and the Tamar estuary. Changes like these point to a system in flux as species jostle for position, adapting their behaviour and altering the geographic range in response to a changing climate.

Pacific oysters need water temperatures of more than 20 C to spawn, and a single female oyster can release up to 200 million eggs in a single spawning event. While the native oysters preferred habitat below the low-water mark keeps them hidden from view, Pacific oysters colonise right up the shoreline, smothering whole beaches, harbour walls and even pontoons, transforming them into jagged and razor-sharp terrain. This makes these areas hazardous for us, and could completely alter vital habitat for wading birds and other species that make the most of the productive mudflats exposed by the tides.

Cornwall Wildlife Trust’s response is to be accepting and pragmatic. “It’s unrealistic to think we’ll be able to eradicate this species, so we’re going to have to learn to live with it and manage it the best we can,” says Matt. “There could be an opportunity here.” The Trust is hoping enterprising members of the public might rise to the challenge and find ways to make the most of this abundant resource. The obvious first port of call is to encourage the seafood industry to take a fresh look at these oysters, normally underrated simply for their wonky appearance.

Before being eaten, oysters must be purified in specially designed aquaria, complete with UV sterilisers, before being sent to market. If markets could be found for oversized and wonky wild-caught oysters, fishermen could play a vital role in controlling populations on intertidal beaches. As many of the oysters are found growing cemented firmly to rocks and harbour sides, however, it is difficult to remove them without damaging their shells, making purification impossible, so an alternative use must be found.

There are also suggestions that the shells themselves could prove to be an abundant, functional and versatile biomaterial. As a great source of calcium and nutrients, they could be ground up and used as soil conditioner, or be turned into a valuable resource for biotechnology.

This could be a chance for Cornwall to do what it does best: flipping a problem into an opportunity, and leading the way in ocean conservation!

Got an idea? Contact Matt Slater at matt.slater@cornwallwildlifetrust.org.uk