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An Overview of Cage Culture

An Overview of Cage Culture. Claude E. Boyd Professor Emeritus School of Fisheries, Aquaculture and Aquatic Sciences Auburn University, Auburn, Alabama 36849 USA. Most Common Species Cultured in Cages. Tilapia – throughout tropics

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An Overview of Cage Culture

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  1. An Overview of Cage Culture Claude E. Boyd Professor Emeritus School of Fisheries, Aquaculture and Aquatic Sciences Auburn University, Auburn, Alabama 36849 USA

  2. Most Common Species Cultured in Cages • Tilapia – throughout tropics • Salmon – Norway and Chile are major producers, but there are several other nations with large amounts of salmon cage culture. Marine. • Trout – Scotland • Common carp – several Asian countries • Vietnamese catfish (Tra and Basa) • Several marine fish species

  3. Advantages of Cage Culture • Applicable to most species of fish • Does not require space on land for grow-out • High density makes management logistics simple • Can be used in most types of water bodies • Inexpensive Infrastructure and simple technology • Consumes very little water

  4. Types of Cages Wooden boxes with slats and openings between Wire cages Mesh cages – nylon or plastic Highly variable in size Smallest are about 1 m3 Largest are 1,500 m3 or more Floating or submerged

  5. Traditional Low Density Versus High Density Cage Culture

  6. Cage Shapes

  7. Lateral Surface Area (LSA):Volume (V) Ratios for Cages of Different Shapes and Sizes.

  8. Mesh Size and Open Space

  9. Flow Comparison for Square and Circular Cages

  10. Positioning of Cages

  11. Positioning of Cages All sides same. C better than B.

  12. Guidelines for Selecting Cage Sites in Lakes and Reservoirs • Pollution free and with low productivity – water clear or mildly green and transparency  100 cm. • No more than 50% of depth devoid of dissolved oxygen during period of thermal stratification. • Water level changes should be known. Minimum depth at least 1 m deeper than cage bottoms. • Wind patterns and water currents understood and considered in selecting cage sites. • Avoid sites with aquatic macrophyte infestations. • Security of fish in cages should be considered.

  13. Factors Influencing Water Quality in Cages • Water quality in water surrounding cages • Rate of water exchange a. Cage design: mesh size and open area in material; cage shape; cage size (LSA:V ratio) b. Placement: orientation relative to water currents; positioning relative to other cages c. Water current rate

  14. Water Quality Issues in Cage Culture • Extreme temperature • Low dissolved oxygen concentration • High carbon dioxide • Low pH and total alkalinity • Ammonia • Nitrite • Hydrogen sulfide • Pollution: nutrients, turbidity, pesticides, heavy metals and other industrial chemicals

  15. Factors Causing Low Dissolved Oxygen • Thermal destratification • Heavy phytoplankton blooms • Phytoplankton die-offs • Prolonged periods of cloudy weather

  16. Factors Causing Thermal Destratification • Decreasing air temperature from summer to fall • Weather fronts with heavy rain and wind • Periods of cloudy, cooler weather • Phytoplankton die-offs

  17. Good Management Practices for Cage Culture • Cages should be designed and constructed to facilitate water exchange and to prevent escapes. • Cages should be installed in macrophyte-free areas with good water quality and water exchange. • Cages should be positioned to enhance water exchange. • Cages should be moved frequently enough to prevent excessive sedimentation. • Apply feeds conservatively to minimize wastes. • When cages are removed for cleaning, debris removed should not be discharged into public waters.

  18. Good Management Practices for Cage Culture • Remove dead fish daily for responsible disposal. • Collect feed bags and other solids wastes for responsible disposal. • Cages should not interfere with navigation or other uses of the water body. • Discourage birds and other predators by non-lethal means. • Wastes from feeding should not exceed the carrying capacity of the containing water body. • Monitor water quality in the containing water body.

  19. Possible Negative Impacts of Cage Culture • Introduction of non-native species through escapees • Spread of fish diseases from culture species to wild fish • Destruction of birds and other fish predators • Interference with local navigation by cage placement • Eutrophication of containing water bodies • Adverse benthic effects from solids settling beneath cages • Conflicts over water use with local people • Product contamination with antibiotics used in culture or with pesticides, heavy metals, or industrial chemicals in site waters.

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