A monoculture ("mono" meaning "one") refers to an agricultural crop that focuses on a single species. Cornfields, pine plantations, and beef cattle ranches are examples of monocultures. A polyculture is a system with a diversity of species that functions more as a natural ecosystem. Monocultures often require outside sources of energy and nutrients, whereas a polyculture is more likely to be self-sustaining.
The Catfish Farmers of America has more than 2,000 members, and more than half of the country's catfish production is in Mississippi. However, one of the most successful catfish operations may well be Butterfield's Alabama farm because of his grasp of ecological principles. A key principle for long-term success in catfish farming, and all other professions that harvest plants or animals, is sustainability. The processes involved in producing the commodity must not cost more in terms of energy and nutrients than the commodity itself is worth.
In respect to catfish, Butterfield maintains that an "intensive catfish monoculture is a very wasteful and inefficient method of producing fish protein." Some catfish farms raise catfish solely, with no or few other fish species in the ponds. According to Butterfield, such operations must import fish meal from outside sources for catfish food. In addition, a catfish monoculture depletes underground water sources because the water must be replaced constantly for cleansing purposes. These and other environmental problems can be avoided by using a polyculture approach.
A critical problem faced by most catfish farmers is the buildup of phytoplankton, the algae that cause algal blooms, which in turn result in decreased levels of oxygen in the water. If toxic chemicals must be used to control an algal bloom, the discarded wastewater pollutes local streams and rivers. Plus, mechanized systems of aeration are necessary to replenish oxygen for the fish.
Butterfield considers that one key to success in catfish farming is to use the phytoplankton (algae) rather than constantly battle it. Butterfield's catfish farming operation is truly a polyculture that addresses the algae problem. For example, along with the catfish, he has stocked his ponds with a variety of other fish species such as tilapia and different kinds of carp. As these fish eat phytoplankton, algal blooms are kept to a minimum. The blooms are a constant hazard to catfish monocultures because they reduce oxygen levels in the water. He has also added bluegill, crappie, and bass, which feed at other levels in the food web of the ponds. Thus the aquatic habitats that harbor catfish operate in a manner closer to that of a natural ecological system. And because natural ecosystems are by definition self-sustaining ones, a catfish pond based on a polyculture is more likely to be successful. Also, the other fish can be harvested later along with the catfish.
The standard method of harvesting fish in a catfish farm is to lower water levels in a pond and then use nets to collect the catfish. As a means of conserving groundwater reserves, Butterfield does not drain ponds but instead pumps water from one pond into another. He then sorts the various types of fish by hand, which he notes is more labor intensive than would be true for a catfish monoculture where only one type of fish is involved.
One aspect of Dan Butterfield's polycultural catfish farming system that I appreciate is that he does not kill birds that come in for a meal of fish from time to time. For example, some catfish farms are a major attractant of cormorants as predators. As Butterfield says, "In the interest of living in harmony with nature, I do not begrudge sharing a portion of my crop." That seems like as good a reason as any to use the polyculture approach.
Source: University of Georgia - Savannah River Ecology Laboratory - Taken From Website July 2006
