Dekweekvanalikruiken - HZ University of Applied Sciences

Abstract
In many countries periwinkles (Littorina littorea L.) are a delicacy. Currently, there is
an increasing demand for periwinkles in the European coastal countries. During the
last few years periwinkles have been imported from Ireland and Scotland, these
countries have a commercial periwinkle fishery. Picking periwinkles takes up a lot of
time and there for involves considerable costs. If research proves that production of
periwinkles on land is profitable from both a commercial and a technical point of
view, this could be an improvement for the aquaculture sector in the Netherlands.
This report contains the results of an exploratory study of the production of
periwinkles under artificial circumstances. The basic principle was a combination of a
phototrophic biofilm reactor and production of periwinkles. The main question in this
study was: Is it technically possible to maintain periwinkles on biofilm under artificial
circumstances?
On the basis of a literature study, three experiments have been formed: maintaining
periwinkles, growth of periwinkles and inducing the reproduction of periwinkles. All
experiments were conducted under artificial circumstances, while feeding the
periwinkles on biofilm.
Maintaining periwinkles fed on biofilm under artificial circumstances is technically
possible. Production of biofilm is easy, both in a phototropic biofilm reactor and on
screens submerged in the inner port of Vlissingen. Results from different experiments
show that older biofilm has al lower food value relative to a phototrophic biofilm
younger than 30-40 days. There is reason to believe that the normal daily demand of
food for a periwinkle lies between 3-4% of the dry body weight.
Inducing the reproduction of periwinkles failed during this research period (October –
December). Conditioning on different temperatures has had no effect on the
maturation of the genitals. The most probable cause is the strong natural reproduction
rhytm of periwinkle, they only reproduce in the breeding season (January – July).
During four weeks of monitoring periwinkles fed on biofilm, the shell has grown
significantly, but not the body weight. Periwinkles of 13 mm showed an average
shellgrowth of 0.29 mm and periwinkles of 18 mm showed an average shellgrowth of
0.24 mm. The absence of growth in the body weight was caused by a food shortage in
the experiment, literature did not correspond with the actual food demand of the
periwinkles. Furthermore the nutritional value (C:N ratio) of the older biofilm could
not be enough to increase the body weight of the periwinkle.
There is also reason to believe that periwinkles take up attached biofilm better than
loose biofilm, although loose biofilm is eaten.
Maintaining periwinkles in combination with the phototrophic biofilm reactor is
possible, provided that the periwinkles are kept apart from the reactor. Periwinkles are
mobile and could block the watercourse.