An Oyster Education, With Porthilly Shellfish

At the end of last year, we paid a visit to Porthilly Shellfish at Rock to learn more about their oysters and to enjoy some of their amazing produce straight from the half shell on the waters edge. Food doesn’t get much fresher than that. The quality of shellfish that we have access to in the UK, and particularly in Cornwall, is exceptional, and we want to celebrate it and encourage more people to eat Cornish shellfish, more often.

porthilly oysters

Oysters are nutritious and a great source of protein. These days they have a bit of a reputation for being an upmarket item only found on the menus of high-end restaurants, but historically they were a really common and affordable food, especially in Victorian-era London. Oysters are also great for the environment and native oysters are a keystone species; they fix carbon as calcium carbonate in their shells, and the reefs created by oyster beds can protect coasts from storm damage. Because oysters are filter feeders they improve water clarity, allowing sunlight to penetrate deeper so that sea grasses can flourish and provide valuable habitats for other marine life. This means that farming oysters is actually good for the body of water that they’re raised in.

the camel estuary at rock and padstow on the north coast of cornwall

Porthilly Shellfish raise oysters and mussels in the Camel Estuary on the coast of North Cornwall, directly opposite Padstow. The Marshall family has been farming at Porthilly for five generations, so although their shellfish operation is very well established it’s relatively new compared to the life of the farm. We spent a morning with farmer Tim Marshall and his nephew Matt, who runs the day-to-day operations of Porthilly Shellfish, talking to them about how they got started in oysters and how they create such an amazing product.

rupert cooper of philleigh way cookery school talking with Matt Marshall of Porthilly Shellfish on the camel estuary

How Oysters Are Farmed At Porthilly

Like a lot of farming, it all starts with seed. Porthilly buy in oyster “seed” from a hatchery who nurture single oyster spats onto fragments of shell and grow them to about the size of a piece of granola (about 7mm x 7mm). The seed gets to Porthilly and is placed in mesh bags that are placed on racks in the intertidal area of the estuary. This is a classic French technique that lifts the oysters out of the sand and mud, and puts them in the best possible place to feast on all of the phytoplankton floating past them.

oyster racks on the camel estuary, cornwall

Porthilly also employ another method with floating racks suspended from a buoy line, that uses the motion of the water to tumble the shells. The oysters will spend up to two years out in the estuary, filtering around 200 litres of seawater per day through their partially opened shells. The team regularly turn over and shake the mesh bags to tumble the oysters around and promote the development of deeply cupped shells, and periodically the bags are brought back to the farm so that the oysters can be graded.

collecting in oysters for grading at porthilly shellfish in cornwall

On the day that we visited, Matt and his team were grading oysters that were about one year old. The oysters are inspected on a conveyor belt, with any empty shells discarded, and then sorted by weight. As the oysters grow they are given more space in the mesh bags – as seed there might be a few hundred tiny oysters in a mesh bag, but as they get towards market size there are only around eight. This sorting is done using a machine that weighs, bags and counts the oysters. “This machine was designed for packing chicken or fish fillets in a food factory,” Tim told us, “but sometimes we’ve got a million and a half oysters to do and when we used bring them in on the back of the trailer and count them in, we’d lose count.”

grading oysters at porthilly shellfish

Harvesting Oysters

Once they’ve reached market size, the bags are collected in and the oysters are unloaded into special saltwater tanks where they spend a few days. Water from the estuary is piped in and passed under ultra-violet lights before it reaches the storage tanks. This process kills any bacteria in the water and gives the oysters the opportunity to “freshen up” and drop any sediment that they may be carrying as excess baggage, without losing the beautiful flavor of their home waters. They’re then ready to be sent off to restaurants or fishmongers.

rinsing oysters prior to grading at porthilly shellfish

How Porthilly Shellfish Started

Tim began farming oysters in 1978. “The farm’s been in our family for five generations,” he told us, “And that means that we owned the land to the mean high water mark. My grandfather bought the foreshore from the then Duke of Cornwall, which is a bit of a grey area in terms of where the foreshore begins and ends. So we own and farm on a stretch on the Porthilly side of the estuary, as well as now having some racks on the other side of the estuary.”

“I used to mess about fishing and picking crabs and going out in the boats. I always thought I was going to have a trout farm of some sort, and make something out in the estuary. But it doesn’t really lend itself to that because it’s too shallow. And then when I was about 15 or 16 an academic came along from what was then Plymouth Polytechnic, who’d seen this system out in France. He asked if he could have a go at it here. He came and spoke to my Dad, who let him do it without charging him any rent. It failed for some reason and he gave up. There was a lovely old chap up the road who was one of my Dad’s contemporaries – a boatbuilder and carpenter by trade and a real character – a salmon poacher too. He was taking some of these oysters and selling them to a fellow in Exeter, and he told me I ought to get into it. He sent me to see his friend, who was using the French system in Exmouth, by Dawlish, so I went up to learn from him. He was really good to me and set me on my way.”

tim marshall of porthilly shellfish talking with rupert cooper of philleigh way cookery school

“Slowly, along with Rick [Stein] and other local chefs pushing shellfish, we slowly grew it. There were times when we struggled to sell them, but I took a trip to France and soon realised what a market there was over there, so that’s where we used to sell most of our oysters to. One year they didn’t want to take any, and it coincided with my son coming home and he wanted to grow mussels as well. We had to put the tanks in to make enough money out of the mussels, and it all just slowly grew on from there. That year that the French didn’t want any, we pushed it much harder in this country and grew the market. I don’t think we realised what a great product we had, compared to some oysters from other parts of the country.

harvesting oysters at porthilly shellfish

Porthilly’s Pacific (Rock) Oysters

There are several different types of oysters that you’ll most commonly find in fishmongers or on a restaurant menu. Each has its own characteristics and flavour profiles, which are then developed further by the environment and conditions in which they grow; this is known in the oyster world as terroir, much like merroir in wine.
Porthilly Shellfish raise Pacific oysters, a variety that originates from Japan but are now the most common variety farmed around the world. “The native oysters don’t like it in the bags,” Tim explained, “They also take five to six years to mature and get to market, whereas these Pacifics take half the time. They’re also more popular, as they’re cheaper and are a bit more accessible taste-wise. Native oysters are much more seasonal. We can harvest these Pacifics all year round, although they’re much better through the winter months.

The Oyster Lady really rates Porthilly’s Pacific Rock Oysters (and if anybody knows their oysters, she does), noting them to be “fresh, clean and creamy, with notes of cucumber and zinc.”

porthilly oyster

Brexit’s Impact On UK Shellfish Producers

Since our visit in December the Brexit deal has crippled the UK’s shellfish industry because of a law that indefinitely bans the export of live bivalve molluscs (oysters, mussels, and clams, for example), both wild and farmed, to the EU from non-member states. The only exception is if they have come from Class A waters or have been purified in depuration tanks (which shortens their shelf life, hence why most exports haven’t been purified). Much of the UK’s inshore coastal waters are categorised as Class B, so almost overnight a huge export market vanished. It’s a small and specialist market (valued at less than £12m/year) but for the people involved, it’s their livelihoods. Our friends at Porthilly shouldn’t be too badly impacted by this development because they have spent many years developing a great reputation and domestic market for their shellfish, and because they have depuration facilities on the farm. We’re glad that they seem to be an exception, but other fisheries (such as the traditional oyster fishery near us on the Fal river) aren’t so fortunate.

You can purchase Porthilly oysters order online from Simply Oysters or Fish For Thought. Once you’ve got your oysters, try out some of our favourite oyster mignonette recipes (click here for the recipes).

a selection of oyster mignonette sauces

If you fancy learning more about cooking with and eating shellfish then click through to find out more about our Half-Day Fish, Fish In A Day, and Advanced Fish Cookery courses.

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