In this thesis, biometric indicators and the chemical composition of oysters, specifically the amount of protein, fat, carbohydrates and water, were monitored for three months. The aim of the research was to determine the suitability of the Krka River for growing oysters in order to diversify the cultivation of shellfish in the Krka area, and consequently for the further development of mariculture in the Republic of Croatia. This research could provide manufacturers with useful information that could also serve the needs of consumers who want to assess the health benefits of shellfish consumption. The results of the chemical composition of the meat of oysters from the Krka River show values that correspond to the values determined in earlier research. Compared to earlier research, there are positive deviations that indicate a positive effect on the meat quality of oysters from the area of the Krka River. According to the results of the research, it is determined that the Krka River is suitable for growing oysters and the further development of mariculture in this area. The results on the composition of oysters also provide useful information to producers and consumers when assessing the health benefits of shellfish consumption, especially oysters.