Oysters are filter-feeding bivalve molluscs that inhabit shallow, sub-tidal and tidal waters that may be fully marine or estuarine.   

There are few more sustainable protein and nutrient-rich foods than oysters because, as filter feeders, they thrive at the base of food chains.  They eat single-celled algae and other tiny organic particles that are naturally present in seawater.  These algae are our planet’s main synthesisers of omega-3 oils, making oysters a rich source of these essential nutrients, comparable in levels to some oily fish that live much higher up food chains.  They are also rich in Vitamin B12 and a source of Vitamin D.*

Some leading organisations involved in seafood sustainability are recommending to consumers that they eat seafood from lower trophic levels, including oysters and other bivalves such as mussels.

* See Seafish’s Love Seafood website for the full nutritional profile

There are two main species of oyster in the UK: the native, or flat oyster, Ostrea edulis, and Crassostrea gigas, the rock oyster. Native oysters have become very scarce, both in the wild and on farms.  They grow much more slowly than rock oysters and are very rarely found in the marketplace.  We farm both species but, like almost all other oyster farms across Europe and globally, our main production is rock oysters. We have very few natives and these are not currently for sale.

Native oysters have been under intense fishing pressure since at least Roman times.  Oysters were so abundant in the wild at one time that parts of London and Manhattan are built on top of ancient oyster middens (waste shell).  But over-fishing, habitat destruction, declining water quality and disease have all contributed to a massive decline in native oyster populations over the past couple of centuries. Fortunately there are several on-going efforts to re-establish them in the wild (in fact we have contributed to one such effort), but this important work will take time.  Rock oysters were introduced across Europe in the 1970s to supplement natives and these have become the mainstay on menus and in farms.  Rock oysters do not appear to breed in the wild in Scotland, where it is probably too cold.

We farm our oysters in the tidal Kyle of Durness, which is a narrow strait through which flows the final few miles of the river Dionard, heading north into the Pentland Firth and North Sea.  The Kyle drains and fills twice a day with the tides, and the farm is situated so that on the biggest tides we can access the trestles to turn, grade, stock and harvest the oysters. 

Oysters are grown over the course of three to five years inside mesh bags that are secured to low trestles that stand on the sea bed.  The farm site was selected for its good water quality, with extremely low risk of pollution, strong currents and excellent water exchange, bringing abundant fresh algae and oxygen to the oysters with each tide.

The oyster farm has become a habitat for all sorts of wildlife, including small fish and crabs, and the Kyle has resident seals and otters. Golden and fish eagles are never far away.

The farm is located in a very remote part of Scotland and, apart from the raft that is moored at its centre, spends most of its time under the water and out of sight.  It is accessible only by small boat or by walking in around half a mile from the road’s end.  Its carbon footprint and environmental impact is very low compared to most farming businesses.  Most of the operations of the farm are by hand.  Only the grading and cleaning of the oysters require small machines.  We also use modest outboard motors and a quadbike.

The baby oysters, also known as seed, are bred at one of the UK’s two oyster hatcheries.  They arrive once or twice a year by courier van in a handful of small boxes, when they are about 7mm across, and are stocked into fine-meshed bags and put out on trestles as quickly as possible.  The work of the oyster farm is then to grade them regularly, maintain the bags, reduce stocking density and increase mesh size as the oysters grow, and finally to harvest them after three to five years.  They are slow food!  Our oysters do tend to get spatfalls of barnacles on them each Spring.  This is annoying for us as farmers but it is also a sign that the water is full of algae and other plankton.  The barnacles would not spawn in such abundance if the food wasn’t there.  What this means is that we have decided to clean the barnacles off before selling the oysters but there will usually be some that we can’t remove.