La. researcher uses light to grow bigger crawfish
Wednesday, July 6, 2011
NEW ORLEANS (AP) — A Louisiana researcher looking into ways to produce more and bigger crawfish in the same space said she’s had success with lighting the ponds at night and believes her work could pave the way for expanding crawfish farming in cooler areas.
Crawfish is one of the nation’s biggest aquaculture crops, with the number of pounds harvested second only to catfish in most years. While Louisiana produces almost all of the fresh — not frozen — crawfish eaten in this country, there are farms at least as far north as the Carolinas and Virginia. Crawfish also are raised in Europe and Australia.
Julie Delabbio, director of Northwestern State University’s Aquaculture Research Center in Lena, said she has found putting underwater lights in crawfish ponds dramatically improves production. Her work is important as the U.S. looks to increase its domestic aquaculture.
Ponds with a dozen underwater lights per quarter-acre produced about one-third to two-thirds more pounds of crawfish than unlit ones, Delabbio said. The work she’s done over the past three years found lit ponds produced 800 to 1,000 pounds of crawfish per acre compared to 500 to 600 pounds in unlit ponds. This year’s harvest was even better: ponds without lights produced about 850 pounds of marketable crawfish per acre, compared to nearly 1,660 in those with lights, she said.
The gains weren’t just in the number of crawfish, but their size.
“Just getting more crawfish isn’t necessarily a good thing if you’re getting a lot of little crawfish,” Delabbio said. “We’re getting more sellable crawfish out of the ponds with underwater lights.”
Using lights to stretch the “day” has been used for decades to speed the growth of chickens, hogs and salmon, but the application with crawfish is new and Delabbio doesn’t know just why it works. She has three ideas: the longer exposure to light may stimulate the animal’s metabolism, as it does with chickens and hogs; the light may stimulate the growth of plankton, plants and insects, providing the crawfish with more food; or the lights may attract smaller invertebrates, creating spots where crawfish can get an easy meal without expending a lot of energy.
“I’d like to pick her brain about that,” said crawfish farmer Robert Buller of Whiteville. “That’s a pretty good increase. I don’t know how you’d get lights all over the farm. But it is a pretty good increase. Especially in a year like this when production is down. That’d be pretty substantial.”
But Stephen Minvielle, director of the Louisiana Crawfish Farmers Association, said experience in the automotive and electric industry taught him how costly it would be to light a pond.
“The economics of running lights of any size in a crawfish pond would run you bankrupt in about a month,” he said. “A one-kilowatt metal ‘halight’ probably burns $65 a month, running it eight hours a night.”
Louisiana’s crawfish farmers averaged 600 pounds per acre for last year, when they got about $168.5 million for their crop. That was about two-thirds of the state’s $252.3 million aquaculture business, with oysters a distant second at $46.5 million.
While farmers in Cajun country sell about 80 percent of Louisiana’s farmed crawfish, Delabbio said she expected interest in lit ponds would come mostly from those in central and north Louisiana, where the season is much shorter — four months, at most, instead of about seven.
“Getting more production with such a short season and such a different climate could be a big help,” she said. And, she’s working to find ways to reduce the cost.
This year, she began looking at whether less-expensive fluorescent lights used to attract shrimp at night would work as well as halogen lights. They seem to, she said, in the 12 quarter-acre ponds at the center where she does her research 30 miles southeast of Natchitoches. She’s also exploring other options.
“With underwater lights, the end result is to try to have solar-powered lights” that could hang from floating platforms, she said.
David Savoy of Church Point was doubtful: Solar panels and batteries are expensive, and underwater lights take a lot of upkeep, he said.
“I’ve got 1,700 acres under water. That’s not even close to feasible,” he said.
Delabbio acknowledged the lights can get scummy over a season and said she’s looking at how long it takes before they’re not effective. She also wants to look at reducing the amount of light to see just how few bulbs and little hours of extra light are needed and whether LEDs will work. While there are obstacles, she remains optimistic.
One thing that excites her, she said, is that lights could provide more crawfish without any need to increase the amount of pond space and water.
“I can’t think of any negative environmental impact,” she said.
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