Better Diets For Farm-Raised Fish Help Lower Pollution

In a project funded by Texas Sea Grant, Drs. Allen Davis and Connie Arnold are studying the nutritional needs of fish and designing diets that provide just enough protein to obtain optimum growth. By developing better-tailored diets and feeding regimes, Allen said, researchers can cut feed costs because farmers will know how much food the fish require. They can also cut pollution because fish excrete less waste when they are fed only what they need, he said.

"The more information we have on nutrition, the more we can optimize how the nutrients are retained by the animal, this not only makes it cost-effective and reduces the pollution load," said Davis, a Sea Grant research scientist at The University of Texas at Austin, Marine Science Institute.

The researchers are also trying to determine the nutrition needs of fish at different points in their life cycles. For example, he said, redfish grow fast, so they need a diet rich in protein very early in their lives. As they grow older, however, they require fewer nutrients, and farmers can turn to the cheaper feeds that contain fewer nutrients.

"A lot of this research is geared towards not only developing the technology and demonstrating that these diets do produce good things, such as fast growth rates, but we're also giving the farmer another option for reducing pollution loads," Davis said.

Well-balanced, protein-rich feeds can reduce the amount of pollutants released into fish ponds by as much as 25 percent, he said. However, these feeds are more expensive than others, and farmers typically go with the cheaper, less nutrient-rich feeds. Farmers may save money in the short-term, Davis said. In the long run, however, they will spend more money on feed because they will have to use more of it. And, he said, they will create more waste.

Already, Texas fish farms are incorporating the diets outlined by Davis and Arnold. Ultimately, the scientists hope to reduce the production costs of shrimp and fish farms while protecting the environment, he said. Protecting the environment is essential to the industry because aquaculture relies on good, quality water.

"In general, pollution from aquaculture is not a major problem, but we want to be proactive as far as maintaining a good environmental perspective," Davis said. "It doesn't do us any good to pollute our own water source. Logically, it makes sense to move towards these lower pollution feeds."