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Net Yield (net + yield)
Selected AbstractsProduction Characteristics, Water Quality, and Costs of Producing Channel Catfish Ictalurus punctatus at Different Stocking Densities in Single-batch ProductionJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2006Brent E. Southworth Channel catfish Ictalurus punctatus farming is the largest component of aquaculture in the USA. Culture technologies have evolved over time, and little recent work has been conducted on the effects of stocking density on production characteristics and water quality. Twelve 0.1-ha ponds were stocked with 13- to 15-cm fingerlings (16 g) at either 8600, 17,300, 26,000, or 34,600 fish/ha in single-batch culture with three replicates per treatment. Fish were fed daily to apparent satiation with a 32% floating commercial catfish feed. Nitrite-N, nitrate-N, total ammonia nitrogen (TAN), total nitrogen, total phosphorus, chemical oxygen demand (COD), Secchi disk visibility, chlorophyll a, chloride, total alkalinity, total hardness, pH, temperature, and dissolved oxygen (DO) were monitored. Ponds were harvested after a 201-d culture period (March 26, 2003 to October 13, 2003). Net yield increased significantly (P < 0.05) as stocking density increased, reaching an average of 9026 kg/ha at the highest density. Growth and marketable yield (>0.57 kg) decreased with increasing stocking density. Survival was not significantly different among densities. Mean and maximum daily feeding rates increased with density, but feed conversion ratios did not differ significantly among treatments (overall average of 1.42), despite the fact that at the higher stocking densities, the feeding rates sometimes exceeded 112 kg/ha per d (100 lb/ac per d). Morning DO concentrations fell below 3 mg/L only once in a 34,600 fish/ha pond. Concentrations of chlorophyll a, COD, nitrite-N, and TAN increased nominally with increasing feed quantities but did not reach levels considered problematic even at the highest stocking densities. Breakeven prices were lowest for the highest stocking density even after accounting for the additional time and growth required for submarketable fish to reach market size. While total costs were higher for the higher density treatments, the relatively higher yields more than compensated for higher costs. [source] Comparative growth and yield of channel catfish and channel × blue hybrid catfish fed a full or restricted rationAQUACULTURE RESEARCH, Issue 9 2010Bartholomew W Green Abstract Growth and yield (kg ha,1) of the channel catfish (Ictalurus punctatus, Rafinesque, 1818) and the channel × blue hybrid catfish [I. punctatus female ×I. furcatus (Lesueur, 1840) male], which shared the Jubilee strain of channel catfish as the maternal parent, were compared in sixteen 0.1 ha earthen ponds (14 852 fish ha,1) during the April to November growing season. Each fish genetic group was fed a commercially formulated 32% protein feed daily to apparent satiation or at 80% of the mean daily satiation ration. Net yield and individual weight were higher for channel × blue hybrid catfish compared with channel catfish and for fish fed a full ration compared with a restricted ration. When fed a full ration, the channel × blue hybrid catfish grew faster from May to September than did the purebred channel catfish because the hybrid catfish consumed a greater percentage of its body weight at each feeding. Net yield within each fish genetic group was lower when feed ration was restricted. The per cent reduction in net yield in response to feed restriction was similar for each fish genetic group. [source] Effect of Multiple-batch Channel Catfish, Ictalurus punctatus, Stocking Density and Feeding Rate on Water Quality, Production Characteristics, and CostsJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2006Brent E. Southworth To quantitatively define relationships among stocking densities, feeding rates, water quality, and production costs for channel catfish, Ictalurus punctatus, grown in multiple-batch systems, twelve 0.1-ha earthen ponds were stocked at 8,600, 17,300, 26,000, or 34,600 fingerlings/ha along with 2,268 kg/ha of carryover fish. Fish in all ponds were fed daily to apparent satiation using 32% protein floating feed. Temperature and dissolved oxygen in each pond were monitored twice daily; pH weekly; nitrite-N, total ammonia nitrogen, and Secchi disk visibility every 2 wk; nitrate-N, chlorophyll a, total nitrogen, total phosphorus, and chemical oxygen demand monthly; and chloride every other month. The costs of producing channel catfish at different stocking densities were estimated. There were no significant differences (P > 0.05) as a result of stocking density among treatment means of (1) gross or net yields, (2) mean weights at harvest, and (3) growth or survival of fingerlings (24,36%) and carryover fish (77,94%). Mean and maximum daily feeding rates ranged from 40 to 53 kg/ha/d and 123 to 188 kg/ha/d, respectively, and feed conversion ratios averaged 1.75. There were no differences in any feed-related parameter as a result of density. Water quality variables showed few differences among densities at samplings and no differences when averaged across the production season. Yield of fingerlings increased as stocking density increased with significant differences between the two highest and the two lowest stocking densities. Breakeven prices were lower at the higher stocking densities as a result of the higher yield of understocked fish and similar mean individual fish weights produced at these higher stocking densities. Overall, varying stocking densities of fingerlings in multiple-batch systems had little effect on production efficiency and water quality. Additional research on managing the population structure of carryover fish in commercial catfish ponds may be warranted. [source] Comparisons of growth and economic performance among monosex and mixed-sex culture of red mud crab (Scylla olivacea Herbst, 1796) in bamboo pens in the tidal flats of mangrove forests, BangladeshAQUACULTURE RESEARCH, Issue 4 2009Mst. Muslima Khatun Abstract An experiment was conducted in a randomized block design to compare growth and economic performance between monosex and mixed-sex culture of red mud crab (Scylla olivacea Herbst, 1796) fed with trash fish at 5,10% body weight per day in the mangrove tidal flat at Burigoaliny Union of Satkhira District, Bangladesh. The experiment had three treatments in triplicate each: (a) all-male culture, (b) all-female culture and (c) mixed-sex culture. Crabs of 80,120 g in size were stocked at a density of 0.5 crab m,2 and cultured for 100 days. Specific growth rates (SGRs) by weight and internal carapace width (ICW) in the all-male culture were significantly higher than those in the all-female culture (P<0.05), while SGRs in the mixed-sex culture showed no significant differences from those in the all-male and all-female culture (P>0.05). No significant differences in final mean body weight, ICW, daily weight gain, survival rate, gross and net yields were found among all the treatments (P>0.05). The area of high water level with mangroves gave significantly better results in terms of feed conversion ratio, survival rate, gross and net yields than the area of low water level (P>0.05). The experiment suggests that the all-female culture in the area of high water level with mangroves could be suitable in developing commercial pen culture of red mud crabs in Bangladesh. [source] |