Louisiana Agriculture Magazine Fall 1999
The most serious problems that face catfish farmers include losses from birdsand diseases, off-flavor and the shortageof labor to harvest fish. These problems have been magnified in recent years asfish farmers have increased stocking andfeeding rates to keep ahead of increasing expenses and competition.
Two serious problems affecting Louisiana aquaculture arethe bacterial pathogens that cause enteric septicemia of catfish(ESC) and photobacteriosis in hybrid striped bass. ESC causes theloss of millions of dollars annually in the catfish industry.
Many of the problems in the catfishindustry are exacerbated by the uncertainty producers face when planning their operations. The sources of risk are numerous,ranging from weather fluctuationsand bird predation to regulatory policy.
Ornamental ponds and water gardens are becoming increasingly popular. It is estimated thatthere are about 40 new ones per week in the vicinity of Baton Rouge alone. This phenomenon offers entrepreneurial opportunities for those interested in aquaculture. These ponds need to be designed, stocked and maintained. Preferable varieties of fish include goldfish and koi.
Although many advances have beenmade during the rapid growth of thecatfish industry, today’s culture practicesare about the same as those developedover 25 years ago.
Although Louisiana already has adiverse aquaculture industry, many morespecies could be grown here or grown ona larger scale. Many prospects present specific problems that could complicate commercial development, but most of these constraints relate to marketing, financing or regulatory considerations, not technical issues.
Sustainability, a concept much discussed in the aquaculture industry,has become associated with the idea that production systems must be designed and sited with consideration of not only their economic viability, but also their long-term environmental and sociological impact.
Most catfish is processed into fresh or frozen fillets and whole-dressed fish. Other products include steaks, nuggets and value-added products, which accounted for 21 percent of the total products sold in1998.
When a gene from one species of plant or animal is inserted in to the genome of another species, the resulting plant or animal is then transgenic.
Crawfish aquaculture in Louisianadepends solely on a forage-based foodsystem for supplying nutrients to thegrowing animals. Because of availableplant residue following grain harvestsand because rice exhibits good regrowth characteristics, crawfish production often follows the rice harvest as a common crop rotation practice
Even though aquaculture, or “farming of the waters,” has been practiced for centuries, it was more “art”than “science” until late into the 20thcentury.
The Aquaculture Research Station is one of 20 branch stations of the LouisianaAgricultural Experiment Station. The facility, which includes more than 200 fish culturetanks, a fish hatchery, an aquaculture greenhouse and a 22,000 square-foot aquacultureresearch laboratory, is three miles south of the LSU campus in Baton Rouge.
The art of feeding fish is thousandsof years old, but the science of fishnutrition began only about 50 years ago.
The two leading diseases affecting the catfish industry are the bacterial pathogens Edwardsiella ictaluri and Flavobacterium columnare(formerly Flexibacter columnaris).
About 10 percent of the annual channel catfish crop is lost to infectious diseases. The most important of these diseases are Edwardsiella ictaluri, Flavobacterium columnare and channel catfish virus.
One problem facing Louisiana’s oyster industry is disease. The major culprits are the protozoans Perkinsusmarinus (Dermo) and Haplosporidium nelsoni (MSX). In the Gulf of Mexico, it is estimated that Dermo infection kills more than half the adultoyster population.
Aquaculture is evolving worldwidebecause of a shortfall of fisheryproducts from oceans and inlandwaters. After World War II, it appearedthat the world’s fisheries resources werevirtually unlimited. World landingsduring 1948 to 1952 averaged 21.9million metric tons per year and rosesteadily until 1968, when increasescontinued but at a slower rate.
Although much genetic research involves developing ways to improve reproduction, it is just as important to develop methods to prevent reproduction.
The domestic crawfish industry isthe only large-scale, commercially viable crustacean aquaculture industry in North America. With more than 110,000 acresof crawfish ponds, Louisiana’s 1,600 farmers produce 35 million to 50 million pounds annually worth $25 million to$35 million at the producer level.
Profitable aquaculture depends on good water quality.Physiologically, aquatic animals respond more intensely to theirenvironment than do terrestrial animals. The stress of poorwater can lead to disease and poor nutrition and growth ofcultivatedaquaticanimals.
The preferred way to cook crawfishis to boil the whole animal in seasonedwater and then serve it so the consumerextracts the abdominal muscle, or tailmeat, by hand.
In much of aquaculture, animals arein high density production systems. Thiscan result in stress from crowding andsub-optimal water quality conditions andprovide for easy transmission of disease.In response to anticipated disease
Geneticists develop maps of DNA molecules to aid in understanding inheritance patterns.One kind of map, called agenetic linkage map, describes inheritanceof observable traits, such as color or shape, and usually involves breeding studiesto compare parents and offspring.
For more than seven decades, catfishfarmers have relied on the warming ofspring to trigger spawning in channelcatfish.