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Could farming these small snails become big business?
For the very first time, researchers have succeeded in nurturing periwinkles in the laboratory.
“There are currently no periwinkle farms anywhere on the planet. People go out and gather the molluscs along the shoreline. But many of the conditions needed for commercial farming are now in place,” Andreas Hagemann at SINTEF Ocean says.
For the first time in Norway, researchers have succeeded in hatching periwinkle eggs, raising the larvae, getting them to attach themselves to substrates, and develop into adult perinkles under laboratory conditions.
“We’ll soon be expanding this project to see if we can get similar results on a bigger scale,” he says.
No stranger on the shore
Periwinkles are not what you get when you order escargots in a French restaurant. Escargots are edible land snails.
The common periwinkle, on the other hand, is a marine mollusc that lives in the intertidal zone. In France, they go by the name of bigorneaux. Anyone can find them along the shoreline. They are the tiny snails you can see crawling around the rocks and among the seaweed.
It is rare to find periwinkles on Norwegian menus, but they are a very popular delicacy in France, Spain, and Portugal - especially at Christmas.
Periwinkles have been transformed from an everyday food to something of an exclusive delicacy. The price per kilo for living periwinkles is currently about the same as that for salmon.
44 tonnes
In 2022, Statsnail AS exported 44 tonnes of wild periwinkles to the European market, but only 500 kilos to customers in Norway.
There is no shortage of shoreline habitats in Norway, but weather conditions mean that the harvesting season is shorter than that in southern Europe. It is thus not ideal for Norwegian exporters that prices are low in summer, but reach their peak as Christmas approaches.
The periwinkles are exported live, after first being kept in tanks containing seawater.
Patience breeds success
SINTEF’s involvement with periwinkles started in 2018.
At that time, the researchers’ aim was to determine the optimal methods for maintaining and feeding the molluscs in captivity from the time of harvest to the approach of Christmas, with the goal of maximising their sale price per kilogram.
The initial project involved using saltwater tanks installed on land. Following their collection from the shoreline, the periwinkles were kept in a recirculation facility. They were provided with a diet of green seaweed, and the results were promising – they thrived and exhibited healthy development.
They also tasted very similar to fresh periwinkles collected from the shore.
Farming on land
“These excellent results led us to look into the potential for farming periwinkles in an onshore facility – from eggs right up to development of the adult snails,” Hagemann says.
The researchers wanted to look into not only how they might create artificial environments that would encourage the periwinkles to reproduce, but also how their eggs could be harvested, matured, and hatched into larvae.
"We also planned to investigate what kinds of food the larvae and adult periwinkles preferred, as well as how fast they developed under different environmental conditions,” he says.
Problems on the substrate
The researchers started with adult periwinkles that were collected from the shore and transferred to a tank.
Periwinkles are highly fertile, and a single female can produce as many as 100,000 eggs per year.
After spawning, the eggs were moved into new tanks with different temperatures and salt concentrations in order to study how these factors influenced development times and survival rates. The eggs hatched, releasing the larvae to swim freely in the water.
However, a problem arose during the next stage.
The researchers failed to identify the conditions needed to enable the larvae to settle on the substrate at the bottom of the tanks prior to their metamorphosis into bottom-living organisms.
First in the world?
A new study was subsequently launched.
The breakthrough finally came after multiple experiments into feed and environmental conditions conducted at the Norwegian Centre for Plankton Technology.
90 per cent of larvae survived to the point at which they were ready to settle on substrates at the bottom of their tanks.
“As far as we know, this is the first time this has been demonstrated under laboratory conditions,” Hagemann says.
After settling on the bottom, the larvae metamorphose into adult periwinkles with hard shells. The process from hatching to the development of adults that attach themselves to the substrate takes about a month.
Biofilms may be the answer
Periwinkles have a powerful foot that protrudes from the shell and is used for mobility. The foot is equipped with a rough, rasping, tongue-like structure that the periwinkle uses to obtain plankton from the biofilm that covers the rocks on which it lives.
SINTEF believes that this biofilm is the key to whether or not a larva will settle on a given substrate prior to developing into an adult.
The researchers are planning to analyse microorganisms both in the sea and in substrate biofilms at locations where Statsnail AS has identified high densities of recently attached periwinkles. This information can be used to further improve development and survival rates in the lab.
Demo facility is just around the corner
Statsnail AS is now in the process of constructing a demonstration periwinkle farm in Norway.
The issue of feed represents a challenge in all types of farming – it can be very expensive and, in some situations, poorly sustainable.
“We’re planning to look into what kinds of microalgae are present naturally in the sea during spring when the periwinkles are spawning,” Hagemann says.
When they have collected samples and analysed the data to identify which species are most abundant in thriving algal communities, they can optimise the feed provided at the farm facility to mimic natural conditions.
"At the start of their lives, periwinkles feed on microscopic phytoplankton before later moving on to bottom-living algae. These are renewable resources produced by sunlight and photosynthesis,” he says.
Conserving wild periwinkle populations
Hagemann is hopeful that the successful lab results can be reproduced on a larger scale.
“As well as producing an invaluable food resource, farming will reduce the pressure on wild populations. One of the benefits of aquaculture is that it is possible to produce and supply food all year round,” he says.
Reference:
Lillebjerka et al. Effects of temperature, salinity and diet on embryonic and early larval development in Littorina littorea (Gastropoda: Littorinimorpha), Frontiers in Marine Science, vol. 10, 2023. DOI: 10.3389/fmars.2023.1240599
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