Fish Culture Systems

1. Fish Culture Systems Extensive culture: low intensity aquaculture providing only small increases over natural productivity. Extensive fish culture systems have low stocking densities, don’t use rearing units specifically engineered for aquaculture, and don’t involve artificial diets Intensive culture: fish culture methods yielding far in excess of natural productivity levels. Intensive systems utilize high stocking rates, man-made rearing units and artificial diets.

2. 4 Types of Intensive Culture Systems 1.) Pond culture: system based on earthen ponds, where some or all of the food consumed is from natural production and there is minimal water flow. 2.) Raceway Culture: system based on circular or straight raceways (tanks) with high water flow and minimal water reuse. 3.) Cage Culture: system in which fish are confined to net pens or cages placed in ponds, rivers, lakes, or ocean. 4.) Tank Culture Utilizing Water Recirculation: tank culture system where nearly 100% of the water is reused and cleansed by sophisticated filtration systems.

3. Advantages of Recirculation Systems 1.) Minimum demand on limited water resources. The limited quantity of high quality water in aquifers and on the surface is an indication that water recirculation systems will become increasingly important as a means of meeting the demand for fish. 2.) Minimum environmental impact. Recirculation systems permit the concentration and removal of fish wastes so that water pollution can be controlled and minimized. 3.) Few government permits are required. Because of limited impact on environment, and limited withdrawal of waste water, few permits are required for aquaculture systems based on water recirculation.

4. 4.) Closed circulation systems can be located near markets. Suitable sites for other systems are dependent on location of suitable water or land resources. Recirculation systems can be located so that transportation costs and time between harvest can be minimized. 5.) Water quality and temperature can be maximized. Water temperature can be maintained at the optimum level for fast growth and optimum feed conversion. 6.) Minimize losses from environmental hazards such as predators, pollutants, and disease. Fish produced in closed recirculation systems are safe from environmental pollutants and many pathogens. 7.) Minimum space requirements for level of production. In comparison to other types of systems, protein production in closed systems require very little space.

5. Disadvantages 1.) High Capital Costs. Capital costs of buildings, pumps, tanks, heaters, etc. are higher than other systems of aquaculture. 2.) High Operating Costs. Closed systems require pumping water though tanks and filters. The operating costs of pumps are significant, and these costs may be the difference between profitable and nonprofitable fish farms.

6. 3.) Vulnerability to Mechanical Failure. Pumps make fish farm vulnerable to breakdowns and blackouts which can result in catastrophic losses of fish. 4.) Difficulties with Fish Health Management. Disease outbreaks, once they occur, are difficult to manage. Pathogens in the system find refuge in the biological filter and are difficult to remove. Often the only option is to treat the fish in the tank, thus killing the bacteria in the biofilter. 5.) Higher level of management is required. Unless managed properly, sub-optimal conditions can occur that will result in disease outbreaks and increased mortality. A much higher level of system monitoring is required than in most other systems.

7. Facilities Needed for Indoor Recirculation Systems 1.) Electricity: ground fault protection should be provided because of the equipment in and around water 2.) Electrical circuits: should have at least 2 separate circuits to allow for the water pump and (if needed) heaters. 3.) Floor drain: in case of water spill or overflow, a drain is needed (especially for emergency situations) 4.) Rearing unit: filters and rearing unit require about 7 ½ feet x 5 ½ feet of floor space. 5.) Storage space: needed for equipment and feed storage 6.) Auxiliary tank space: additional tank space 7.) Operating room: enough space (min. of 3 ft.) around the system to allow for ample room to feed, harvest, clean,etc. **Additional items to consider: lab space & weight of system

8. ASSIGNMENT TO BE COMPLETED BY END OF CLASS: 1.) What are four basic types of intensive fish culture systems? 2.) What are the advantages of utilizing a water recirculation system for raising fish? 3.) What are disadvantages of a water recirculation system for raising fish? 4.) Define the following terms: net pen, water quality, capital, extensive culture, intensive culture