Reducing Size Variation in Hybrid Catfish Culture Through Graded Partial Harvest

Hybrid catfish (♀ channel catfish Ictalurus punctatus x ♂ blue catfish I. furcatus) are becoming a major contributor to catfish aquaculture in the United States. Because of unique production characteristics of hybrid catfish, rapid farmer adoption of hybrids has outpaced appropriate management research. This study was conducted to determine the effect of mid-summer partial harvest of faster-growing fish on production characteristics of hybrid catfish in single-batch culture. Twelve, 1.0-acre ponds were stocked with 10,000 hybrid catfish (~ 0.12 lb/fish) in mid-March 2015. In August 2015, six random ponds were partially harvested to remove fish larger than ~1.25 lb using an in-pond, flexible-panel grading sock. In October 2015, all ponds were completely harvested. Partial harvest of faster-growing fish removed ~26% of fish from ponds in August. Removal of faster-growing fish resulted in 0.9% of the total crop considered "out-of-size" (> 4 lb/fish) and subject to discounts, compared with 2.1% of the fish from the control ponds.  (Figure 1). However, reduction of fish numbers by mid-summer partial harvest reduced overall production by an average of 16% in the partial-harvest treatment compared with control ponds. Overall, partial harvest of faster-growing fish in mid-summer reduced the overall biomass of discounted, out-of-size fish.  Higher production in control ponds resulted in greater net revenue.