Due to its elongated shape, the ecological conditions of Mali Ston Bay depend more on the influences from the mainland than from the open sea. Specific hydrology results in extremely favorable conditions for shellfish life, including Mali Ston oyster. Favorable conditions in Mali Ston Bay provide habitat for 89 species of shellfish, out of which only two species, oysters and mussels, are farmed. The consequences of the freshwater input from the river Neretva, submarine springs and precipitation washing off the mainland make the particular conditions of Mali Ston Bay waters in terms of salinity, temperature and the amount of nutrients. The interaction and the seasonal variation of these properties determine the specific ecological balance of the bay. The constant inflow of freshwater regulates the temperature and currents in the bay and contributes to high concentrations of nutrient salts. Nutrient salts are the basis for the high production of phytoplankton populations i.e., unicellular algae which are oyster’s food. Oysters feed by filtering the sea water during which they collect phytoplankton. Oysters can filter up to 200 liters of sea per day. The specific natural characteristics of Mali Ston Bay make it one of the rare sea surfaces in Europe where the reproductive potential of the flat oyster is high enough that the farming process is still based on collecting the spat exclusively from the natural environment.