Collecting The Oyster Spat
Oysters from the genus Ostrea differ from the other oysters by fertilization. It does not occur in the open sea but inside the female’s shell after the males release the gametes into the open sea and the females collect them through filtration. The females keep the small larvae for a while, after which they release them into the sea to increase their chances of survival. Once in the open sea, the larvae float with the sea currents for a while, after which they begin sinking to the seabed. Unlike the other areas, the specificity of Mali Ston Bay is that oysters spawn here twice a year, in spring and autumn. It is interesting to note that one adult oyster can produce up to 2 million larvae in one cycle. It is also interesting that oysters are hermaphrodites and they change their sex several times during their life.
The oyster spat is collected from the nature. Farmers prepare collectors i.e., different base for collecting the spat and they place them on special locations along the seabed. During the collection period, sea currents bring small oyster larvae onto these collectors, they attach and this marks the beginning of the breeding process.
Different materials are used for collecting juvenile oysters. In the past, sheaves of wooden branches were used and today collectors made from plastic nets are mostly used. The collectors are installed when there is a sufficient concentration of oyster larvae in the water column.
Breeding of juvenile oysters to market size
Net collectors can be segmented, after which oysters continue to grow on the same surface to which they were attached. Individual nets created by segmenting the net collectors are called pergolari. Together with the attached juvenile Mali Ston oysters, they are hung on floating installations where they can grow to their market size.
Small oysters removed from the collectors continue their breeding process to the market size in different types of nets or crates. Juvenile oysters are put in baskets (crates) or nets which are tied to floating lines. Crates and nets are continuously taken out so shellfish density is lowered. During this period of around one year, the oysters reach an adequate size for the next stage of farming.
The most common technique of farming Mali Ston oysters to the market size is cementing. The oysters are attached with cement to the plastic rope, 2 to 4 meters long. One such rope contains from 40 to 80 oysters. After the cement gets dry, ropes are installed to floating parks, where oysters continue their growth to the market size.
The farming cycle from laying down collectors to reaching the market size of the Mali Ston oyster takes two to three years. During this time, each oyster passes through the hands of the farmer around 5 times. Modern farming of Mali Ston oysters occurs on floating parks. Navigability of the parks is maintained by the buoys, while floating lines are anchored on both sides by concrete anchors.
The oldest technology was based on throwing the oak, spruce or olive tree branches into the sea and extracting them with adult oysters. Every oyster farmer had a special location for throwing the branches, which he would extract after 3 years and then harvest the oysters.
Later on, the more advanced technology was putting the wooden pillars into the seabed. A lot of pillars, tied together with coconut ropes, formed a park or a sea garden. Wooden pillars were replaced by concrete and iron pillars until the appearance of floating parks. The remains of these structures which were used in the past are still visible throughout the bay.