Aquaculture

For years there have been predictions that the fast-growing marine aquaculture species, cobia (Rachycentron canadum), is about to take off, but so far it has been hard to spot on the market. If you want cobia, it seems you either have to catch it yourself (it is a great game fish in Australia and southern USA), or you have to go to Asia

Modern feeds are high-tech products. They offer fishes and crustaceans in aquaculture everything they need for their existence and ensure that the organisms grow fast, remain healthy and develop normally. But who knows exactly what such feeds contain? There is probably no area of aquaculture where so many rumours are rampant, or where so much is assumed, speculated and alleged as in the feed sector.

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.

Sturgeon stocks are threatened worldwide by extinction. Various factors have led to a dramatic drop in populations during the last two decades. Since aquaculture can make a considerable contribution towards saving wild sturgeon and satisfying demand for “black caviar”, Aquatir Ltd decided in 2005 to build a modern recirculation system for farming sturgeon.

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.

The vision for the future of European freshwater aquaculture – and the research and innovation needed to supports its key strategies - will be the focus of the first of a series of thematic workshops organised by the EU Aquainnova initiative. The workshop will be held in Warsaw, Poland at Sofitel hotel, from June 15-16, 2011.

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

Chapter Three: Fish species in recirculation

A recirculation system is a costly affair to build and to operate, and production must be efficient in order to make a profit. Selecting the right species to produce and constructing a well functioning system are therefore of high importance. Essentially, the aim of the production is to sell the fish at a high price and at the same time to keep the production cost at the lowest possible level.

Chapter Four: Project planning and implementation

The idea of building a recirculation fish farm is often based on very different views on what is important and what is interesting. People tend to focus on things they already know or things they find most exciting, and in the process forget about other aspects of the project.

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