24 SEPTEMBER 2012 Paddlefish can be grown in aquaculture ponds as a source of roe, used to make caviar, and flesh. When stocked in commercial catfish ponds, paddlefish represents an additional fish species that can be grown without the need for a specifically prepared diet. Processed paddlefish caviar and flesh could increase profits for catfish producers. Juvenile paddlefish can be sold for fisheries stock enhancement or mitigation, or grown out for food fish in large ponds, lakes and reservoirs. A demonstration project was conducted to determine required harvest effort and to estimate costs and evaluate overall feasibility of selling small quantities of paddlefish caviar and flesh. Growing Paddlefish in Catfish Ponds Eight 2-ha channel catfish ponds in western Kentucky were stocked with 375 paddlefish fingerlings (30-40 cm) per ha in 2002. These ponds contained 12,400 mixed-size catfish per ha, managed with a multiple-batch cropping system. Replacement catfish fingerlings were stocked yearly. Food-sized channel catfish (1-2 kg) were not likely to prey on paddlefish of the size stocked (Tidwell and Mims 1990). Depending on stocking density, the presence of paddlefish in catfish ponds can affect phytoplankton and zooplankton populations (Burke and Bayne 1986). However, it is unclear if catfish growth is affected by stocked paddlefish. Each pond was seined to harvest catfish six or more times during the year. From 1-5 t of fish for fee fishing ponds were harvested during spring and summer. Fish processors would occasionally buy 9-t loads of catfish. Harvesting costs for three different volumes of catfish (without paddlefish) were estimated in Table 1. During catfish harvest, paddlefish were returned to the pond across the seine or moved to a different pond, thereby delaying the harvest process. Approximately 30-45 minutes were required to transfer paddlefish over the seine. A loss of approximately 3000 catfish during the summer of 2010 was at least partially attributable to delayed harvest caused by removal of paddlefish from the seine. Mortality induced by handling may occur in both species during sorting and harvest at water temperatures >28 C. Estimated labor costs were $1920 ($240 per year) for the 8-year period required for females to mature. Paddlefish survival was less than 5 percent over the duration of the project. Reasons for poor paddlefish survival were not clear but mortality may have been caused by overstocking, low dissolved oxygen events and bird predation. Juvenile paddlefish are typically stocked at 250 fish per ha (Mims and Shelton 2005) rather than the 375 fish stocked per ha for the demonstration project. Paddlefish are less tolerant of low dissolved oxygen concentration than channel catfish and paddlefish mortalities occurred at concentrations < 2 mg/L. During periods of low dissolved oxygen, paddlefish tended to swim into the rotating blades of paddlewheel aerators. The resulting lacerations or trauma to paddlefish may have caused mortality. Paddlefish Harvesting and Processing Paddlefish Polycultured in Channel Catfish Ponds: A Demonstration Project Forrest Wynne 1 TABLE 1. Estimated cost to harvest three quantities of channel catfish. Quantity (kg) Cost ($/kg) < 2,268 0.57 2,268 – 4,545 0.26 > 4,545 0.13 TABLE 2. Expenses for paddlefish processing. Live paddlefish: 1923 kg @ $1.10/kg $2,115.30 Paddlefish roe: 22.7 kg @ $99/kg $2,247.30 Live transport of fish (from Murray to Bellevue, KY) $1,550.00 Processing facility: 3 mo rent and utilities $2,971.00 Labor: 290 hours @ $10.00/hr (excluding drive time) $2,900.00 Live transport of fish (from Bellevue to Mount Sterling, KY) $2,216.00 TOTAL: $13,999.60 TABLE 3. Revenues from paddlefish products. Fillets: 159 kg @ $12.10/kg $1,923.90 Caviar: 22.7 kg @ $756.80/kg $17,179.36 TOTAL: $19,103.26 Catfish ponds may best serve as a paddlefish nursery where fish are raised for one or two growing seasons, followed by stocking into lakes or reservoirs for grow-out.
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