REWILDING

RESTORATION & CONSERVATION PROJECTS

Kilchoan Native Oyster Restoration Project
The Native oyster (Ostrea edulis) is distinct from the commonly sold and non-native pacific oyster (Crassostrea gigas). The much slower growing native oyster has a rounder shell and is less tolerant of environmental variation than the robust pacific oyster. Until the beginning of the 19th century native oysters played an important role as a common food source for both the rich and the poor. They were commonly found around the coast of Scotland. However, in the later part of the 20th century around 90% of the oyster stocks had been depleted due to overharvesting, diseases and a decrease in suitable habitat and water quality. As well as being a food source, oysters provide a variety of environmental services in the Scottish marine habitats. They act as ecosystem engineers; creating reefs, filtering water and storing carbon as well as providing a food source for other wildlife. An adult native oyster can filter up to 240 litres of seawater in a single day. They store carbon in a three-dimensional structure on the seabed called oyster reefs which act as a nursery and spawning ground for a variety of marine organisms all whilst depositing carbon & nutrients onto the seabed in their faeces.

Kilchoan Estate are currently restoring the native oyster population in Loch Melfort by annually growing 28 000 hatchery raised native oysters in cages suspended from our existing pontoon. In 2023 we increased our nursery capacity to hold 114 000 oysters by adding growing cages to our seaweed farm. When the oysters in the growing cages reach 10-12 grams, they will be released at pre-surveyed sites along the shoreline of Loch Melfort creating a self-sustaining and resilient population.

Flapper skate survey

Dipturus intermedius is the largest of all European skates and rays (Superorder: Batoidea). It is an elasmobranch, meaning that, like sharks, they have cartilaginous skeletons. They predate on benthic species including crustaceans, teleost fish and smaller elasmobranchs as well as some pelagic prey. Females are larger than the males and can reach up to 3m in total length and over 2m from wingtip to wingtip. They are classified as Critically Endangered by the IUCN (International Union for Conservation of Nature) Red List of Threatened Species.

Historically this species was known as the ‘common skate’, but this comprised two different species, the flapper and the blue skate (Dipturus flossada). Both have been described as extinct in large parts of their range following a long period of exploitation by fisheries; this coupled with the fact that individuals can take up to 10 years to reach maturity and produce offspring, means that populations will be slow to recover from  negative impacts.

Both species are found in coastal waters of the European continental shelf and slopes in the north east Atlantic, more specifically the smaller blue skate is found around Rockall and in the Celtic Sea where its range overlaps with the flapper skate. Flappers are found in higher numbers in the northern North Sea and the West Coast of Scotland, although there are the occasional reports of adults being sighted off the Northeast coast of Scotland too.

Flappers, like all skates, reproduce by laying egg cases. Recent observations indicate that females select small boulder covered habitats in relatively shallow waters to deposit their egg cases. The egg cases themselves are reasonably tough and can be seen in clusters slotted in between these small boulders. If undisturbed, they remain here for more than 17 months before hatching.