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Title: EFFECTS OF WATER TEMPERATURE ON SOCK GRADING OF SUBMARKETABLE CHANNEL CATFISH, ICTALURUS PUNCTATUS, IN EARTHEN PONDS

Author
item Pfeiffer, Tim
item Freeman, Donald

Submitted to: Journal of Applied Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2003
Publication Date: 9/30/2004
Citation: Pfeiffer, T.J., Freeman, D.W. 2001. Effects of water temperature on sock grading of submarketable channel catfish, Ictalurus Punctatus, in earthen ponds. Journal of Applied Aquaculture. 16(1/2):60-64.

Interpretive Summary: The passive sock grading method used by commercial catfish farmers to grade and reduce the number of undersized fish delivered to processing plants was assessed on an experimental scale. The assessment was conducted at the Aquaculture Research Station at the University of Arkansas, Pine Bluff in quarter acre experimental earthen ponds. A rectangular holding sock was that was 3 feet wide, 8 feet long, and 4 feet deep was used. The mesh size of the experimental sock was 1.75 inches and the mesh material was nylon netting. Seventeen groups of channel catfish were graded, with group weights ranging from approximately 250 pounds to over 800 pounds. Fish were held in the sock for approximately three hours (+/- 15 minutes). The water temperature during the trials ranged from 7.3 C to 28.7 C. The percent removal of fish less than one pound during the three hour holding period ranged from 27.6% to 73.3%. The lower grading efficiencies of the sock method were observed at water temperatures below 10 C. At water temperatures above 15 C the sock grading efficiency varied little from the better sock grading performance at warmer water temperatures.

Technical Abstract: The passive sock grading method used by commercial catfish farmers to grade and reduce the number of undersized fish delivered to processing plants was assessed on an experimental scale. The assessment was conducted at the Aquaculture Research Station at the University of Arkansas, Pine Bluff in 0.1 hectare earthen ponds. A rectangular holding sock was fabricated with dimensions of 0.9 m in width, 2.4 m in length, and 1.2 m in depth. The mesh size of the sock was 4.4 cm and the mesh material was nylon netting, 0.64 cm in diameter. Seventeen groups of channel catfish were graded, with group weights ranging from approximately 115 to 370 kilograms. Fish were held in the sock for approximately three hours (+/- 0.27 h). The water temperature during the trials ranged from 7.3 C to 28.7 C. The percent removal of fish less than 0.45 kg during the three-hour holding period ranged from 27.6% to 73.3%. Sock grading efficiency had a decreasing linear relationship with increasing loading density (kgs fish per m3 sock volume) and load ratio (percent small fish to large fish).