February 15-18, 2009 Washington State Convention Center Seattle ...

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DEVELOPMENT OF A FLEXIBLE PANEL FISH GRADING SYSTEM
David Heikes
Aquaculture/Fisheries Center
University of Arkansas at Pine Bluff
Pine Bluff, AR 71601 USA
dheikes@uaex.edu
A flexible panel grading system has been designed and fabricated. The grading panels consist of short lengths (10.25”) of
sunlight resistant rigid pvc conduit (1/2” schedule 40) strung on galvanized aircraft cable (3/16”, 7x19 construction) with industrial
plastic spacers. The individual panel dimensions are approximately 4’ by 20’. The individual apertures can be produced
in 1/8” increments (ie. 1.84”, 1.965”, 2.09”, etc) through various combinations of commercially available industrial spacers.
Three flexible grading panels (2.09” aperture) were fabricated and sewn into the sidewall of a standard–built harvesting sock
60’ long with 1” mesh. Preliminary tests indicate that this design allows hybrid catfish to passively grade without any other
major change to harvesting operations. Farm workers can handle and crowd fish from the modified sock in a similar fashion
to standard socks.
Additionally, work has begun to determine the optimal aperture for grading hybrid catfish with the flexible grading apparatus.
Three small test panels (4’ x 5’) were fabricated with 1.84”, 2.09”, and 2.34” apertures. These panels were incorporated into
three small socks designed to hold 2000 lbs of catfish each. Figure 1 shows the number of hybrid catfish retained by the various
bar apertures as compared to the population prior to grading. Fish were allowed to passively grade overnight (approx.
12 hours). This grading system makes passive sock grading a realistic option for harvesting food-size channel x blue catfish
hybrids and possibly other commercially produced species.