World Aquaculture 31 61 percent) in ponds with Secchi disk measurements that ranged from 30-35 cm just prior to harvest. Ponds with the lowest Secchi disk readings would have had the most zooplankton, promoting better growth of paddlefish. The Secchi disk reading greater than 60 cm indicated clear water and that very few zooplankton were available for paddlefish to feed on. Clear water may have made the juvenile paddlefish more vulnerable to bird predation as well. This and a substantial aquatic weed (Najas guadalupensis) problem could have accounted for poor paddlefish survival in that pond. Postlarval shrimp were stocked at 39,520/ha in the Hopkins Co. pond and 24,700/ha or 29,640/ha in Todd Co. ponds. In Hopkins County, 566 kg/ha of shrimp were harvested after 114 days. The average harvest yield from Todd Co. ponds was 797 kg/ha after 131 days. Shrimp harvested from ponds stocked with paddlefish grew well. Shrimp from the Hopkins Co. pond were approximately 35 count (shrimp/kg) at harvest and those in the Todd Co. ponds were 18-22 count. These results were within the range of those previously observed at both sites (Wurts 2007). With an overall average individual weight of 346 g, the paddlefish harvested were of suitable size for stocking into lakes, reservoirs and food fish production facilities. The results of this demonstration suggest that paddlefish might provide a suitable supplemental crop for low-input shrimp farmers and a means to harvest plankton that otherwise would be lost when ponds are drained at harvest. Polyculture of paddlefish with freshwater shrimp could increase pond yields without increasing feed and fertilizer inputs. Assuming an average paddlefish survival of 50 percent and a retail price of $3.00 each for stockers, the gross value added through polyculture could be US$1,482/ha. Furthermore, it may be possible to stock paddlefish fingerlings at higher densities while achieving similar survival and growth. Raising and selling paddlefish stockers might provide a supplemental crop and additional income for low-input shrimp producers in Kentucky. Notes 1Presented at: Aquaculture America 2008, Feb. 10, Orlando, FL. Harvested shrimp Table 1. Secchi disk measurements and paddlefish survival in low-input shrimp ponds. County Secchi Disk Survival (cm) (%) Hopkins 30-35 43 Todd-A 30-35 61 Todd-B >60 10 2Kentucky State University Cooperative Extension Program P.O. Box 469 1205 Hopkinsville Street UK Research and Education Center Princeton, KY 42445-0469 USA www.ca.uky.edu/wkrec/Wurtspage.htm References Wurts, W.A. 2004. Organic fertilization in culture ponds. World Aquaculture 35(2):64-65. Wurts, W.A. 2007. Low input shrimp farming in Kentucky, Macrobrachium rosenbergii. World Aquaculture 38(4):44-49.
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