that ponds were stocked during April and October of each year with producers having the flexibility to understock fingerlings in ponds with existing catfish. Extensive catfish producers typically stock a large fingerling, 45 g, 1 8.5 cm, to ensure good survival and fast growth to market size (Wurts and Wynne 1995). Fingerling price was assumed to be US$0. l 6/fish. Fish were harvest ready when they exceeded a target size of 568 g. Harvesting and hauling charges were included as a unit cost on every kilogram of fish harvested. Annual survival rate was assumed to be 90 percent (Wurts and Wynne 1995). Catfish growth rates, under low stocking densities, were adopted from Masser et al. (1994) and Wurts and Wynne (1995). Using this information, a 45 g catfish stocked in April reached 608 g at the beginning of November (average growth rate = 2.62g/day). However, a 45 g fish stocked in October took 365 days to reach 586 g, because the fish experienced negligible growth from December to February. Feeding rates for extensive stocking densities are available in Tucker et al. (1979). Stocking density was constrained so the maximum feeding rate had an upper limit of 34 kg/ha/day. Winter feeding practices were based on channel catfish feeding trials in Kentucky, which reported that the fish should not be fed at water temperatures less than 7.2°C (fingerlings) and 1 0°C (adult fish). Water temperature data from central and western Kentucky, during November through February, were deemed too cold for feeding catfish. Feed prices were adopted from Hanson and Sites (2004), after adding a feed transportation cost from Arkansas to Kentucky. Using the above assumptions, we developed an economic model of a hypothetical extensive catfish farm in Kentucky. This model provided the optimal stocking densities over a 10 year operating cycle of catfish ponds, breakeven prices for channel catfish sold to consumers and pay lakes, and income opportunities for the catfish farm. The goal of the model was to maximize the income made by a catfish farm and net of all cash costs over a 10 $25,000 $20,000 $15,000 � Investment: ne\ ponds $10.000 � Investment: renov. ponds $5.000 $0 0.4 ha 0.8 ha l.2 ha 1.6 ha Farm size (\\!lier hectares) Fig. 1. Investment requirements for a small-scale extensive catfish farm with 1, 2, 3, or 4, 0.4 ha ponds, categorized by new ponds or renovated, existing ponds. Table 1 . Breakeven price for extensive channel catfish farms with 1, 2, 3, and 4, 0.4 ha ponds. Number of ponds (water area) Breakeven price in US$/kg 1 (0.4 ha) 2 (0.8 ha) 3 (1.2 ha) 4 (1.6 ha) year time period. Labor and management were provided by the farm family and were not a cash expense. To capture economies of scale we considered farms with 1, 2, 3, and 4 ponds, which typify the range of ponds available in small scale farms. To accurately reflect real world constraints faced by small scale Kentucky farmers, we assumed that farm operations were financed by an initial investment, followed by catfish revenues and that there was no further borrowing of money. Results Pertaining to Selling Food Fish Investment requirements for a small-scale extensive catfish farm were illustrated in Figure 1, for four farm sizes. These investment figures include the cost of land, new or renovated ponds and equipment. If an extensive catfish farmer was trying to sell only foodfish, our model indicated that a profit-maximizing farmer should stock 2,950 catfish/ha every spring, and an additional 450/ha every fall. Using this stocking plan, the annual yield would be 1,700 kg/ha. Breakeven prices, above cash costs, are provided in Table 1, for four farm New ponds Renovated Ponds $2.77 ($1.26) $2 .44 ($1 . 1 1 ) $2.16 ($0.98) $1.80 ($0.82) $1.95 ($0.89) $1.58 ($0.72) $1.83 ($0.83) $1.50 ($0.68) sizes. These prices are categorized with respect to whether a producer was using new ponds or renovated existing ponds. If a producer was using a few new ponds and a few existing ponds, the breakeven prices would be between the corresponding levels indicated in Table 1 for a given number of ponds. The breakeven prices showed that, when compared to intensive catfish farming, it was more costly to raise catfish under an extensive culture system. Breakeven prices under intensive systems are usually less, approximately US$1.54/kg on total costs. This result highlights that a low-technology approach is not necessarily a low-cost method of production. Since the breakeven prices in Table 1 exceeded US$1.50/kg, selling fish in wholesale markets and to processing plants would not be profitable for most small-scale extensive catfish producers, because processing plants typically pay from US$1.20-l.63/kg. Kentucky extension specialists indicate that several hundred kilograms of fresh catfish are sold each year to end users at prices not below US$2.20/kg (liveweight). Table 1 shows that a producer would be able to profitably sell catfish at US$2.20/kg, provided they are operating at least WORLD AQUACULTURE 1 5
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