Native oysters (Ostrea edulis) have been harvested from Chichester Harbour since Roman times, but due to overfishing, disease, pollution and competition from invasive Pacific oysters (Magallana gigas), the population has declined by 96% over the past century.
The Solent Oyster Restoration Project is working to restore reefs by reseeding them with juveniles and installing cages containing a high density of mature broodstock beneath pontoons, to facilitate the release of millions of larvae.
Because the oysters are sourced from the River Fal in Cornwall and grown on in Anglesey, any parasites or non-native organisms that could pose a threat to the Solent’s flora and fauna must be removed before their deployment. I was one of 260 “biosecurity volunteers” recruited to give the 20,000 oysters destined for the UK’s largest subtidal native oyster reef a pre-release spa day.
After a briefing, we donned lab coats and nitrile gloves and gathered our supplies – buckets of water, brushes and forceps. Crates of oysters were deposited on each bench, and we set to work. First, scrubbing off silt and algae, paying special attention to the hinges, which trap debris, then inspecting for hitchhikers.
Most were encrusted with calcareous tubeworms (Spirobranchus triqueter), their chalky white casts cemented to the shells like dental calculus. There was something oddly satisfying about cracking them off, especially when they came away in one piece. Slipper limpets (Crepidula fornicata) were more difficult to prise loose. Some had fused to the oysters’ growth plates, forming composite structures.
Not every oyster made the cut. Those that failed to close when squeezed three times were presumed dead and set aside to be ground down to “cultch”, which is spread on the seabed for oyster larvae to settle on and attach. One gaping shell revealed a stowaway juvenile shore crab, which was feasting on the mollusc’s rotting flesh.
By lunchtime, the benches were slick with seawater and shell fragments, and a faint briny odour clung to our clothes. While we sat outside, eating pizza and watching a pair of fox cubs standing on their hind legs to peer into the holding tanks, the oysters soaked in a chlorine bath to eliminate any microscopic pathogens before being weighed, measured and boxed up for their final boat journey.