Fish Farms

An article called Farmed Fish on page 3 of the June '92 issue of USA Today magazine describes how farmed fish lack a fishy smell and taste. Excerpts of the article follow:

Aquaculture is the world's fastest-growing food-producing industry, according to the Institute of Food Technologies. Its defenders say that it is an economical way of making easily available a highly nutritious food, without incurring the great environmental and occupational hazards of commercial fishing. ... And, with the exception of a case of toxic algal bloom traced to farmed shellfish, health and environmental problems have as yet been few in the United States. ... Cooks say that penned fish are flaccid for lack of exercise, and often flavorless because they eat packaged feed. ... Most people, of course, don't like strong flavored fish, which accounts for the phenomenal popularity of some kinds of farmed fish - especially channel catfish, once a strong-flavored fish.

An article called Urban Oasis on page 74 of the January '95 issue of Popular Science magazine diagrams a technique for creating a synergy of plant and fish growth with sewage purification - all in an urban Tokyo setting! Excerpts of the article follow:

Four cylindrical tanks, lit by fluorescent lights and filled with water, contain spirulina algae. The algae absorb nutrients from human waste pumped into the tanks. They also take up carbon dioxide and release oxygen. As they multiply, the algae spill over into an aquarium holding tilapia fish. The fish eat the algae, and the fish-tank effluent is sprayed on the roots of a camphor tree dangling in the air above the fish tank.

An article called Firewater Fish on page 99 of the August '91 issue of Scientific American magazine describes the productivity and challenges of growing fish in indoor tanks. Excerpts of the article follow:

Brown-Forman corporation .. is taking a plunge into another market: fish farming. ... Brown-Forman has chosen the most technically difficult path to enter the business. Rather than raising fish in outdoor ponds, the facility in Louisville relies on indoor tanks in which water is recirculated as many as 30 times a day. ... The technical challenge is to remove fish waste from the series of narrow, five-foot-deep tanks, called raceways. A two-stage process uses filters lined with bacteria that first convert the ammonia secreted by fish through their gills into nitrates, which are flushed out. Another filtration system rids the tanks of solid wastes. ... The technology also allows for more intensive production: a million gallons of water can yield a million pounds of fish, an amount 200 times greater than that for fish raised in ponds.

An article called A feast of Gene-Splicing Down on the Fish Farm on page 512 of the August 2, '91 issue of Science magazine describes how faster growing and more disease resistant farmed fish are developed via gene-splicing. Excerpts of the article follow:

Fish eggs ... are large and readily accessible - deposited by the thousands in open water. As a result, researchers are making rapid progress in tweaking the genes of salmon, trout, catfish, and other farm fish. ... [Researchers] hope to serve up "domesticated" fish that, thanks to genetic engineering, will reach market weight faster than natural strains and will also be hardier - more resistant to diseases and to freezing in winter. ... [Thomas Chen's group at the University of Maryland's Center for Marine Biotechnology in Baltimore] pioneered the technology in carp and rainbow trout. ... The transgenic fish and their offspring both grew from 20% to 46% faster than ordinary specimens.

Other researchers are taking a different tack for boosting aquaculture productivity: Genetically boosting survival rather than growth. John Spense, director of the Canadian Aquaculture R&D Council of Vancouver, points out that fish farms lose much of their potential revenue to diseases. .. [There] are no commercially available remedies or vaccines for fish viruses. So Chen and others are dreaming of ways to engineer immunity into their fish.