Oyster seed between 3mm & 7mm are placed into our specially designed rearing pods. These pods have been built to allow a carefully controlled flow of water to pass over these tiny creatures allowing them to feed as and when they like. These nursery pods are in a sheltered sea loch which is tidal, allowing a good and sustainable feed source for our oyster spat. The feed is supplied by the pristine waters of the Atlantic Ocean surrounding this beautiful island in the Outer Hebrides. As the oysters grow they are graded by size.
The faster growing ones are moved to baskets suspended from rafts, in much deeper waters off shore, allowing the smaller, slower growing ones more chance to develop.
THE TECHNICAL BIT >>
Oysters are bivalve molluscs which feed by filtering seawater through their gills, extracting plankton from the water as a source of food. Bivalve molluscs characteristically have two half shells which hinge at one point. Other common bivalves are mussels, cockles, scallops and razor clams. In order to grow, bivalves filter seawater removing naturally occurring micro-organisms known as plankton. They grow by adding new shell to the edges of each of their valves. This leaves growth rings on the shell allowing the bivalve to be aged by the shell rings. The rate of growth in bivalves is determined by food availability and temperature.
Our oysters arrive with us a “seed” stock much of which is as small as 3mm across. At this size they look like coarse grit. Seed oysters are fragile and need careful nurturing if they are to thrive. To this end we use a raft based FLUPSY.
FLUPSY being short for FLoating UPweller SYstem. This allow us to increase the flow of water through the oysters in an environment where they are constantly submerged, free from physical damage and free from predators. Increasing the water flow brings more naturally occurring plankton passed the oysters and gives them better opportunity to feed and grow. Oysters can be in the FLUPSY for several months before they are ready to move to the next stage.
Once the oysters reach 14mm they are transferred into plastic trays, which have slots on the side to allow water to flow through them. These trays continue to offer protection from predators while offering as much natural water exchange as is possible.
The oysters are laid out one layer deep so all have access to fresh water and food. The trays are then made up into stacks of 10 and suspended under a raft. Every 4 weeks the oysters are taken from the trays and cleaned, graded and returned to a fresh clean tray. Grading and cleaning reduces competition between oysters and ensures they still get optimal access to food. The Oysters can spend more than a year in this part of the growth cycle before moving on to the next part of the process.
Once they are large enough, the oysters are moved to plastic coated steel mesh trays. Oysters in these trays are generally large enough to with stand most predators. The trays are strong but allow a high level of water flow, allowing rapid growth. Once again the oysters need to be graded and the trays kept clean to ensure maximal growth. Oysters can be in these trays for well over a year.
Once the oysters are big enough they are moved to the shore where they are placed in plastic mesh bags, on steel trestles. Even on the shore they need regular attention. Bags of oysters are turned at each low tide to stop weed growth on them and to ensure they are evenly distributed within the bags. The trestles are in the intertidal part of the shore which means the oysters are exposed to air twice a day as the tide falls. This “trains” the oysters to close when they are in air, which means that when they are harvested they have a longer shelf life. When on the shore the action of waves tumbles the oysters removing rough edges, known as frill, from the shells and leaving a smoother clean finish.
