Effects of Water Temperature on Sock Grading of Sub-Marketable ChannelCatfish, Ictalurus punctatus, in Earthen Ponds

摘要

The passive sock grading method used by commercial channel catfish, Ictalurus puntatus, farmers to grade and reduce the number of under-sized 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-ha 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 ( plus or minus 0.27 hours). The water temperature during the trials ranged from 7.3 degree C to 28.7 degree C. The percent removal of fish less than 0.45 kg during the three-hour holding period ranged from 27.6% to 73.3%. Overall, sock grading efficiency increased with increasing water temperature and at water temperatures above 15 degree C a greater percentage of fish less than 0.45 kg were not retained in the socks.