Hatchery revives Britain’s nearly extinct local oysters
Decimated by overfishing and pollution, British oysters could make a comeback as a hatchery in the harbor town of Portsmouth, which is helping revive a native species.
At the University of Portsmouth’s Institute of Marine Sciences, huge piles of empty oyster shells are stacked in the yard, ready to welcome the young oyster larvae.
“In the wild environment, the oysters will spawn approximately from May to September, and we hope this will be mimicked here in the hatchery,” said Luke Helmer, scientist at the Blue Marine Foundation, who co-initiated the project. in 2015 with the University of Portsmouth.
The hatchery is the first in Britain to focus solely on the conservation of oysters, without any commercial motivation. It aims to reintroduce millions of European flat oysters (ostrea edulis), a nearly extinct species in this region.
At the center of the research center is a small room filled with saltwater tanks that contain the adult oysters that will lead their rebirth.
The team of scientists “feeds them, maintains the right conditions,” Helmer said.
The team of eight researchers will soon begin to slowly increase the temperature of the water to match that of nearby seawater, which will prompt the oysters to release their larvae.
Oysters reproduce by male oysters releasing sperm into the water, which fertilizes the eggs released by female oysters. The larvae first drift in the water, but then search for an oyster shell to attach themselves to and live in.
At the hatchery, the larvae will live in incubators before being released in June in the Solent, a shallow strait next to the laboratory.
Human intervention is needed because oysters have almost disappeared from the Solent in recent decades.
“If you go back to the 1970s, there were about 15 million oysters taken out of the fishery each year,” Helmer said.
“It has now shrunk to next to nothing.”
Across Europe, the population of this oyster species has fallen by 90 percent since the late 19th century, according to the University of Portsmouth, and is nearly extinct in some areas.
The reasons are “mainly overfishing and harvesting,” said Monica Fabra, PhD student in marine biology.
Other factors include pollution and the introduction of non-native species that compete for space and food, she added, especially the Pacific oyster.
Also known as the “Japanese oyster”, it was introduced in the last century to compensate for the decline in the number of native molluscs and is now the main species in Europe. It turned out to be a very invasive species that has a profound effect on the ecosystem and has driven out the European oyster.
“Breeding them in the hatchery is a safer environment,” said Fabra, gently handling Grand Ma, who is over 15 years old and as big as a hand.
Here, “we can make sure that they survive until the very end of production”, when they enter the sea, she added.
Although it will take some time to reverse the decline in the oyster population, Helmer hopes to reintroduce “somewhere between half a million and a million larvae” into the Solent within the next year. If successful, these will help clean up the water.
Each oyster can filter up to 200 liters of water per day (4.4 gallons), “which is a phenomenal amount,” Helmer said.
They once played a huge role in improving water quality in the region when you factor in the millions of oysters that lived on the seabed.
“Oysters are known to be ecosystem engineers, so they improve the environment,” because of their constant filtering, he added.
The oysters will also improve the biodiversity of the reef where they settle, as their shells can be home to many other species, Fabra said.
In a preliminary test, researchers put oyster cages in the sea and were stunned to put them together and find 97 species.
This result is particularly spectacular for European oysters as they have evolved to live alongside local species, he said.
In addition, some studies have shown that the European oyster may be better adapted to global warming than that of the Pacific.
The hatchery’s findings could quickly be replicated across Europe, as researchers collaborate on similar projects in Germany and the Netherlands.
But Helmer warns that a commercially viable population is still a long way off and it may take a decade to taste delicious local oysters in Portsmouth.