In the early 1980s, East Coast
fishermen peddled striped bass to fish markets, netting up to 14.7 million
pounds annually. Eventually, however, overfishing and pollution essentially
destroyed the industry.
Fish farmers of the East Coast, Arkansas, and California thought the fish
could make a comeback in aquaculture ponds and fill a market vacuum. Thanks
partly to research, they were right. Since 1984, when production was at only
10,000 pounds a year, it has increased to more than 15 million pounds annually.
Actually, it's a hybrid fish called sunshine bass that's making the splash.
A cross between male striped bass and female white bass, sunshine bass grow
faster than either parent.
Fish farmers Mike Freeze of Keo, Arkansas, and Jackson Currie of Wilmot,
Arkansas, are among the leaders in the sunshine bass industry. Freeze
specializes in spawning the parental stocks. He and Currie then nurture the
just-hatched fry from the time they are barely visible2 to 5 millimeters
longuntil about 35 days later when they're 3/4- to 1-inch-long
fingerlings. They then sell the juvenile fish to other farmers around the world
who grow them to market size at 1.5 to 2 pounds in 18 months.
At the ARS National Aquaculture Research Center in Stuttgart, Arkansas, fish
biologist Gerald Ludwig examines a market-size sunshine bass.
To identify production problems
and find solutions, Gerald M. Ludwig, a fish biologist at
ARS' National Aquaculture Research Center
at Stuttgart, Arkansas, keeps in contact with Freeze, Currie, and other
producers. "We learn as we bounce ideas off each other," says Currie.
In the early 1980s, after experimenting with raising microscopic animals
called rotifers as fish feed, Currie turned some equipment over to Ludwig.
Putting the equipment to good use, Ludwig steadily found ways to improve the
survival rate of young fish.
"Until a few years ago, we could achieve only a 10-percent survival
rate of fry," said Ludwig. "Now the norm is 30 percent, and some
nursery pond managers do much better."
Ludwig and his colleagues developed information to help fry culturists time
the stocking of ponds so the fish can eat and grow fast enough to avoid being
eaten by zooplanktonsome of the very creatures they must consume to
survive. Graphs and equations Ludwig developed show the pivotal window of
opportunity when two other essential food sources, rotifers and minute
crustaceans called copepod nauplii, become abundant and zooplankton are still
too small to be a threat.
The equations take into account pond temperature, which strongly influences
the buildup of rotifers, and rainfall, which helps drive the growth of the
copepod nauplii. Other influences that help determine the proper stocking time
include day length, dissolved oxygen levels, and air temperature.
The research may improve the culture of additional tasty fish species like
yellow perch and walleye. If technology affords consumers year-round choices
from among several cultured species, steady buying habits may develop. Then
fish farmers may not have their resources lying idle much of the year.
Ludwig and his colleagues are also researching ways to manage fish so
they'll spawn all year long. That means they need to develop the know-how for
providing a year's supply of live, appropriately sized zooplankton. Ludwig's
plan also calls for growing rotifers and copepod nauplii in ponds or indoor
tanks and redesigning a device called a rotating drum filter to harvest them.
Larger zooplankton will be freeze-dried for enriching diets as the fry grow
into large fingerlings ready to be moved into production tanks.By
Ben Hardin, Agricultural
Research Service Information Staff.
This research is part of Aquaculture, an ARS National Program (#106)
described on the World Wide Web at
Gerald M. Ludwig is at the Harry
K. Dupree Stuttgart National Aquaculture Research Center, USDA-ARS
National Aquaculture Research
Center, 2955 Hwy. 130 E., Stuttgart, AR 72160; phone (870) 673-4483, fax