Question of the Week
Answer: Polyculture is growing two or more species together to take advantage of inherent trophic characteristics and increase marketing opportunities. Some species will grow well together, especially if they have similar (i.e., vegetarian) or different (i.e., fed species vs. filter feeders) feeding habits. Other characteristics to consider are optimum water temperature, methods of harvest, and marketing options. A good example of compatible species are catfish and bluegill, where catfish are bottom feeders and bluegill forage in the water column.
Fed species (i.e., finfish) combined with extractive species (i.e., shellfish) utilize different trophic levels and where wastes of one species becomes food for another. An example of this would be raising salmon with shellfish. For information on shellfish aquaculture, visit the ATTRA’s Ecological Seafood and Aquatic Plant Farming section of the ATTRA website.
Raising two fed species together can be done if there is little chance of depredation of one species on another, particularly during the fingerling stage. An example of this would be raising catfish with carp and tilapia. Carp and tilapia are plankton eaters, but will also eat catfish pellets. Another option is raising tilapia together with freshwater shrimp, if the tilapia are grown in cages.
It is usually not advised to raise tilapia with bass, as tilapia are a major prey of bass. However, they can be grown in a polyculture if the correct ratio of bass to tilapia is achieved. Stocking ponds with tilapia broodfish can supply some forage for bass, while allowing for a harvest of both bass and tilapia. A good paper to review on this topic is Polyculture of Largemouth Bass with Blue Tilapia: Using Blue Tilapia as Forage.
It’s best as a beginner to start small and with the tried and true species combinations, as discussed above. For more detailed information on specific species in your area, I recommend contacting a SeaGrant Educator, who will have experience with aquaculture methods, species, and markets in your area. Contact Virginia SeaGrant for more information.
To learn more about aquaculture, consult the following resources:
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