09/10/1991

Pump Harvesting Systems May Have Future in Catfish Industry

AUBURN, Ala.—By tapping into the latest information and technology, commercial catfish producers have made great strides in the production and processing of their crop. Now they can siphon a little know-how from Auburn University scientists to "pump up" their harvesting methods.

According to Len Lovshin, an Auburn fisheries researcher working with the Alabama Agricultural Experiment Station, the advances made in growing and processing fish have out-paced harvesting techniques.

"Most people still use the boom-and-basket system," he said, adding this system has been effective, but producers want and need a faster, more efficient method.

To help identify new harvesting options, Lovshin and other Auburn scientists participated in a multi-state research effort to evaluate various pump systems that have been used successfully to harvest trout and salmon.

The study, coordinated through the Southern Regional Aquaculture Center, compared the traditional boom-and-basket system to a vacuum pump, which uses positive and negative air pressure to move fish from the water to the transport truck, and a turbine pump, which uses a propeller-type system to load fish. Auburn researchers evaluated speed and efficiency of harvest, trauma and physical stress caused by the devices and survivability and growth of fish subjected to the harvesting procedures.

According to Lovshin, the study showed that the turbine method was the fastest system of the three tested, loading an average of 650 pounds of live catfish per minute. In comparison, the boom-and-basket system loaded approximately 340 pounds per minute and the vacuum pump loaded only 120 pounds per minute.

Lovshin noted that all three systems resulted in some stress and injury to the fish, though the turbine system seemed to cause the greatest amount of stress and more skin abrasions than the other two systems. Still, stress indicators returned to normal within a short time after harvest, regardless of the harvesting system used, and the skin abrasions caused by the turbine pump were not severe enough to affect the marketability of the fish.

Few puncture wounds, which Lovshin explained would "physically damage the muscle and could reduce the value of the fillet of that fish," were found on fish subjected to any of the harvesting systems. Evaluation of survivability and growth of the fish after harvest showed little difference among the three systems. The results did suggest that harvesting fish of a uniform size or adapting the harvester to handle larger fish may increase survivability.

Results of these studies suggest that the boom-and-basket system remains the most practical harvesting choice at this time, but the turbine pump holds promise for the industry.

"If they are loading fish to go to the processing plant where they will be slaughtered in a manner of hours, we think that the turbine pump has very good potential," Lovshin said.

The greatest limitation for this system may be acceptability of the measurement system used in the pump models. Lovshin explained that the pump systems use volume displacement of the water, not traditional scales, to determine pounds harvested.

"If you put anything in water, the water level will rise at a consistent rate," he said. "If you know the area of your hauling tank, every one-inch increase in height equates to a given weight of fish. A sight gauge allows harvesters to watch the water level and measure the weight. "The industry has not used anything like that. They have always used the scale, and there may be a problem with acceptability of this new system," he predicted.

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By:
Katie Smith