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Polyculture of Paddlefish and Catfish
Polyculture of paddlefish with channel catfish is a system designed
for producing yearly harvest of paddlefish for meat. Paddlefish
should be stocked large enough so as not to be preyed on by the
catfish. In production ponds, more than 12 inches is the recommended
size. In catfish fingerling ponds, less than 12 inches is suitable.
Since paddlefish feed on natural zooplankton, there is a certain
carrying capacity of fish that can be grown per surface area of
the pond based on the amount of natural food present. Ponds that
are more than five years old typically have an established food
base favorable to paddlefish; newer ponds should be assessed before
stocking. For example, in Kentucky, we had an average fish survival
of 29 percent in ponds that were only two years old as opposed to
75 percent in ponds that were six years or older. Paddlefish stocked
at 100 fish/surface acre should exhibit a growth rate of about 0.5
pounds/month producing 5- to 6-pound fish in a year with about a
75-percent survival rate.
Paddlefish can be harvested using the same net or seine as catfish.
Seines are typically large enough to encircle the entire area of
the pond. In the middle of the seine, there is an attachment known
as the sock, which is 10 to 15 feet long and allows the fish to
congregate. Socks are of different mesh sizes to permit the grading
of fish, allowing small fish to be released back into the pond and
larger fish to be harvested and processed. During this grading process,
paddlefish can be easily removed by hand sorting. The fish are relatively
docile, and the paddle provides a convenient handle to catch the
fish. In catfish fingerling ponds, using a seine with one-inch mesh
will permit the release of small catfish and only retain the paddlefish.
Paddlefish can be held in holding nets in the pond then loaded onto
hauling truck for transport to the processing plant.
Catfish ponds are not recommended for growing mature female paddlefish
for roe. Catfish ponds present a higher level of risk for caviar
production than reservoir ranching due to possible mortality from
frequent handling of the paddlefish during catfish harvest or low
dissolved oxygen (<2 ppm). However, some producers have taken
the risk and have been successful in producing caviar and meat by
careful water quality management and infrequent harvests. Farmers
who have raised paddlefish for several years in the same pond use
gill nets to selectively remove only the paddlefish. Gill nets of
four-inch mesh or larger will usually not catch catfish, and the
paddlefish are easy to remove alive. This method is easy, but the
gear may need special permitting by state officials for use as aquaculture
harvesting equipment.
See table 1 (below) for a comparison of two
production strategies for paddlefish.
Advantages and Disadvantages of Polyculturing
Paddlefish with Channel Catfish
Paddlefish between 5 and 6 pounds grown with catfish in ponds should
increase production yields by 300-500 pounds as well as profit margins
between $100 to $200/acre compared to growing only catfish in ponds.
Paddlefish are docile and relatively easy to harvest and sort from
catfish. Farmers have reported better water quality such as lower
ammonia and nitrite levels with paddlefish stocked in catfish ponds.
Test markets have demonstrated a strong acceptance for paddlefish
meat, which provides a new fish product for market diversification.
There are some disadvantages to using paddlefish in polyculture
with catfish. Large numbers of stocker fingerlings (>12 inches)
are currently not available. Because of the limited supply, prices
of fingerlings are high (> $3). Paddlefish can not tolerate low
dissolved oxygen (< 2 ppm). They are vulnerable to bird predation,
especially at night, when the fish has a tendency to swim near the
water surface. Markets are not well established because of lack
of consistent supplies of cultured paddlefish.
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