Evaluation of a Mechanical Grader to Separate Fingerling Channel Catfish, Ictalurus punctatus, into Length Groups

Abstract

A Fischtechnik fingerling grader and bioscanner counter were evaluated for speed and accuracy in grading and counting channel catfish, "Ictalurus punctatus," fingerlings. Channel catfish fingerlings ranging in total length from 90 to 280 mm were graded into 110- to 140-mm, 140- to 170-mm, 170- to 200-mm and >200-mm length groups and counted. A sample of the fingerlings was manually separated through grader boxes with 109 mm (7/16 inch), 141 mm (9/16 inch) and 172 mm (11/16 inch) bar spaces to compare length variation within size groups with the mechanical grader. The accuracy of the bioscanner counter was tested by comparison with hand countintg. Fingerlings weighing 679 kg were mechanically graded and counted in 56 minutes, a rate of 12.1 kg/minute. Standard deviation for length within size groups was 10.9, 13.5, and 24.0 mm for the 109-mm, 141-mm, and 172-mm grader boxes, respectively; and 13.4, 12.6, 13.0, and 16.4 mm for the 110- to 140-mm, 140- to 170-mm, 170- to 200-mm and >200-mm mechanical grader length categories, respectively. Length variance within size groups was statistically lower for the mechanical grader compared with the box graders (P < 0.05). The bioscanner counter averaged a 5% overcount of channel catfish fingerlings compared with the manual count (P < 0.05).