Growth, yield, dressout, and net returns of bighead carp Hypophthalmichthys nobilis [Aristichthys nobilis] stocked at three densities in fertilized earthen ponds

摘要

Three studies were conducted in 0.10-ha earthen ponds to evaluate the effect of stocking density of bighead carp (Aristichthys nobilis) on growth, yield, dressout yield and net returns. Initially, bighead carp (average weight of 0.36 kg) were stocked at rates of 500, 320, or 130 fish/ha with 3 replicates for each treatment. Stocking rates for 2-year-old fish (average weight of 2.45 kg) were reduced to 320, 220 or 130 fish/ha in the second year. Net yields of bighead carp stocked at 500 fish/ha (963kg/ha) were higher (P<0.05) than net yields at 320 fish/ha (771 kg/ha), and these were greater (P<0.05) than net yields at 130 fish/ha (369 kg/ha) in the first growing season. Net yields in the second growing season did not differ between stocking densities. There were no differences among treatments in yearly growth which ranged from 11-17 g daily in the first and from 6-13 g daily in the second growing season. Dressout percentages for whole-dressed, steak, shank fillet, and shank fillets with white meat only were also not affected by stocking density. Enterprise and partial budget analysis indicated that monoculture of bighead carp in fertilized ponds is profitable only in the short run at average livehaul market prices, because revenue exceeded variable but not fixed costs. The negative net returns, when all costs were accounted for, indicated that it is not profitable to construct ponds solely for monoculture of bighead carp.