Edible clams, mussels and oysters
The Adriatic Sea is home to about 250 different species of shellfish, with mussels and oysters being two of the most well-known. There are two traditional shellfish farming locations that are also natural habitats: Lim Channel and Bay of Mali Ston. Although clams are primarily used in nutrition, the limestone base of their shells offers versatile applications in agriculture, farming, medicine, and arts.
- Name of Material in the local and Latin language
- Dagnja - crnogorka, datul, denga, klapunica, kućica, kunjka, mušula, pajić, pedoć, pizdica, uš, ušenak (Lat. Mytilus galloprovincialis); Kamenica - oštriga, ostrega, loštrga, loštriga, ostriga (Lat. Ostrea edulis)
- Type of Material
- Organic
- Commonly Found Locations
- Clear, shallow bays with muddy soil and fresh water inflow, which lowers salinity and favors the growth and spawning of shellfish: Mali Ston Bay and Lim Channel, Croatia
- Major Industrial Producers or Suppliers
- Bay of Mali Ston: Obrt Štica, AP Brijesta, Obrt Božović, Obrt Dagnja, Obrt Braća Lazić, Obrt Petra; Lim channel: Emil Sošić, the last shellfish farmer on Lim
- Colour
- Mussel: black-blue, black-brown, sometimes with visible dark brown or purple-blue radial streaks. The interior of the shell is pearly white, with wide blue or purple coloring along the edge. Oyster: grayish, resembling stone, the interior of the shell is pearly white, sometimes containing green, reddish-brown, or blue-gray spots. The meat inside the shell can vary in color from creamy beige to pale gray, with a flavor ranging from salty to delicate and a texture from tender to firm.
- Melting/Boiling Point
- Around 100°C
- Structure
- The shell is constructed of several layers: an outer thin layer called the periostracum, three calcareous outer layers, a middle layer built of leaflets, and an inner nacreous layer called the hypostracum.
- Chemical Composition
- Composition of mussel: 82% water, 10% protein, 5% carbohydrates, 2% inorganic substances, 1% fat; Composition of shell: CaCO3, Aragonite 60%, Calcite 40%
- Industrial and Crafts Applications
- The cultivation of shellfish has traditionally been an artisanal effort, but national plans aim to encourage the development of modern industry to enable aquaculture to contribute to the socio-economic development of coastal and island areas. Around 3000 tons of mussels and 2 million oysters are cultivated each year in Croatia.
- Historical or Cultural Uses
- Shellfish farming started growing significantly in the late 1800s when the first shellfish companies in Mali Ston and Lim Channel were founded.
- Environmental Impact
- Commercial shellfish farming along the Adriatic coast involves cultivating mussels and oysters in specially controlled areas that undergo constant monitoring. The farming technology is clean and requires a pristine natural conditions. Environmental risks include anthropogenic pollution, toxic algae infestation, and bioaccumulation of hazardous substances.
- Innovative or Emerging Applications
- Considering the increasing trends in research and applications of biomass, solutions are being found for the shells of oysters and mussels that remain after consumption. For example, experts in aquaculture at the University of Dubrovnik proposed grinding oyster shells into a moldable powder.
- Extraction Methods
- The cultivation of mussels and oysters is carried out using a system of parks, which can be either permanent or movable, with hanging or stretched nets or ropes. Wild mussels are scraped off with special tools called scrapers, on flat stone surfaces called kunjkars or dredgers. They are also caught by diving and extracting them by hand.
- Processing Techniques
- When a mussel is ready for consumption, pergolas are lifted from the sea and put into a machine for separation, washing and selection.
- Sustainability and Environmental Considerations
- Although mussel farming technology is environmentally friendly as it does not further pollute the environment, large areas of cultivation sites are often undesirable due to the developed tourism on the Adriatic coast.
- Recycling and Waste Management
- The limestone base of the shells is a powder similar to flour or gypsum obtained by grinding. In addition to being moldable, it is useful in agriculture for improving soil quality, in livestock and poultry farming for animal feed, in healthcare for making artificial hips and replacing damaged bones.
- Interesting Facts or Historical Anecdotes
- The Ston Oyster Festival is held in Brijesta on the Pelješac peninsula (Croatia) in March, when the oysters are of the best quality. People from Betine village on Murter Island were well-known for farming shellfish. The locals used a tool called 'brganja' to gather them from the sea. It has been said that the oyster: refreshes, calms, and reminds of love.
- Regulations or Restrictions
- Based on the Order on the Protection of Fish and Other Marine Organisms, mussels must not be caught, collected, or put into circulation if their length is below 5 cm. In 2020, the oyster was registered in the register of protected designations of origin and protected geographical indications and is protected throughout the European Union. Protected species of shellfish include the date mussel (Lithophaga lithophaga) and the noble pen shell (Pinna nobilis).
There are two locations for traditional shellfish farming on the Adriatic coast: the Lim Channel and the Mali Ston Bay. Both locations are natural habitats, as well. While the shellfish farming is still a small-scale endeavor, national strategies aim to encourage the development of modern shell-fishing industry.
Commercial shellfish farming takes place in specially controlled areas that are under constant monitoring. This industry requires a clean natural environment and does not produce additional pollution. However, the cultivation areas may be under the influence of anthropogenic pollution, and there is a risk of the presence of toxic algae or other dangerous substances.
The first shellfish farming companies on the Eastern Adriatic were founded at the end of the 19th century. Their products quickly earned international recognition, including a top award at the 1936 World Exhibition in London for the quality of Ston oysters. In 1888, oyster farming began in Lim Channel by submerging oak branches as anchorage for future shellfish.
The technology of mussel farming is simple and occurs in three phases. It begins with the attachment of larvae to collectors – bundles of branches thrown into the sea. This is followed by removing the units from the collectors and cementing the mussels.
Mussels are harvested year-round, with the highest yields in warm months when they are most abundant.
In the cultivation area, mussels take about two years to reach market size before they can be harvested. The first stage of mussel farming involves collecting juveniles on various types of ropes, which are then transferred to plastic mesh tubes – called pergolas – after about 6 months. Harvesting is done using a vessel resembling a small factory – everything is mechanized, from shell extraction to washing and sorting mussels for sale based on their size.
In addition to being important in nutrition, shells were traditionally used to craft various decorative items such as necklaces and buttons. Crushed shells were also used in production of clothes dyes and as an additive to building materials. Today, the local researchers are once again exploring the possible applications of powdered oyster shells. The powder is similar to flour or gypsum, and in addition to modeling, it can be used in agriculture to improve the quality of the soil; in livestock and poultry farming for animal nutrition; in healthcare for making artificial hips and replacing damaged bones.
