Growing and farming of sea fish and seashells has a great perspective, as in Croatia as well as in complete EU. The increasing healthy diet trends classify sea fish and shells to be among the most desirable food. Farmed products impose as the only alternative to declining supply from the catch, and at the same time represent products which guarantee full control and traceability. The fish farming in an appropriate environment, meeting good manufacturing practice, ensures continuous supply of high quality food at affordable prices. In addition to providing a viable alternative to over-harvesting of natural resources, aquaculture contributes to job creation and growth in coastal and islands areas. Mariculture in Croatia could play a greater role in the development of rural coastal communities than that of today. However, the increase of fish farming, public concern for environmental issues, is suggesting a need for more responsible development and management of the sector. There are opportunities and challenges for effectively integrating mariculture into coastal zone management with equal rights and obligations. The greatest opportunity for the development of new technologies in the sector of aquaculture has the captivity tuna fattening and breeding. One of the biggest threats in this activity are limited natural resources highlighting the long-term sustainability as the only chance for further development of this activity, which plays a major role in employment on the islands, both in the primary activities as well as supporting activities. The company that makes a step towards sustainable development through the application of new technologies will become the market leader. It is not only the competitive advantage between competing companies in Croatia, but the Croatian advantage that can exploit their potential in the production and export as the most essential part of the economy. It will be important for sustainable development of national aquaculture to offer a healthy and quality sea farmed product in quantities that can fulfill market needs with production that does not degrade the marine environment.