Aquaculture

Recirculation aquaculture is essentially a technology for farming fish or other aquatic organisms by re-using the water in the production. The technology is based on the use of mechanical and biological filters, and the method can in principle be used for any species grown in aquaculture such as fish, shrimps, clams etc. Recirculation technology is however primarily used in fish farming, and this guide is aimed at people working in this field of aquaculture.

Chapter 2: The recirculation system step by step In a recirculation system it is necessary to treat the water continuously to remove the waste products excreted by the fish, and to add oxygen to keep the fish alive and well. A recirculation system is in fact quite simple. From the outlet of the fish tanks the water flows to a mechanical filter and further on to a biological filter before it is aerated and stripped of carbon dioxide and returned to the fish tanks. This is the basic principle of recirculation.

Chapter Two: The recirculation system step by step (continued) Mechanical filtration Mechanical filtration of the outlet water from the fish tanks has proven to be the only practical solution for removal of the organic waste products. Today almost all recirculated fish farms filter the outlet water from the tanks in a so called microscreen fitted with a filter cloth of typically 40 to 100 microns. The drumfilter is by far the most commonly used type of microscreen, and the design ensures the gentle removal of particles.

Chapter Two: The recirculation system step by step(continued)

Ukraine is among the European states with the lowest water resources. While average per capita water supply is 4,600 m³ in Europe, it is just slightly over 1,000 m³ in Ukraine. Despite the critical situation with water resources, Ukraine has a certain potential for the development of fisheries, particularly aquaculture. The total area of continental waters which are of interest for fisheries is 1.7 million hectares (Figure 1). Of this, reservoirs constitute 1,078,000 ha (63.2% of the water surface), which is significantly higher than the area of lakes and estuaries (402,200 ha; 23.6%), or that of specialized ponds (208,600 ha; 12.3%).

Among the objectives of the European Maritime and Fisheries Fund are support for the development of sustainable aquaculture. Each EU member draws up a strategic plan for aquaculture for the period 2014 to 2020, which documents its vision and priorities for the sector. Implementation of the policies that lead to the achievement of this vision is supported by the EMFF. Several of the Eurofish member countries that are also members of the EU have drawn up these strategic plans for the aquaculture sector. These plans reflect the very different aquaculture industries and priorities in the countries.

Diseases are functional disruptions which can have adverse effects on the existence of all living organisms, including fish. In natural habitats such as rivers, lakes and seas, fish diseases often go unnoticed. In aquaculture systems, however, they are more easily recognized, particularly since high stock densities promote spreading of infection. Fighting these diseases is difficult because the necessary drugs are lacking or they are not authorized. This creates a state of emergency when therapy proves impossible.

Although cobia (Rachycentron canadum) is still unknown to most consumers it is generally considered to be one of the most promising candidates for marine aquaculture. It is an excellent food fish. It grows extremely fast and is relatively robust. Its firm, white flesh has a nutty, buttery flavour and is rich in Omega 3 fatty acids. Everywhere, where cobia is already available on the market, demand is growing. Aquaculture production is rising.