Reservoir ranching of paddlefish

Paddlefish Polyodon spathula (30-67 cm total length, TL) were stocked in si x flood control reservoirs (< 41 ha) in western Kentucky in January 1995 at a target stocking density of 10 fish/ha. Fish growth was monitored quarter ly be.-inning in July 1995. The fish were implanted intraperitoneally with passive integrated transponder (PIT) tags. Chemical and physical variables and zooplankton biomass were measured monthly. Three reservoirs that had no t been stocked were sampled monthly as controls. Of the 1,440 paddlefish st ocked, 353 were recovered at harvest in the fall of 1996, and only two tags were found. Anecdotal evidence indicated some loss to predation by larger mouth bass Micropterus salmoides and some to escapes through mechanical spi llways. The total gross yield was 1,715 kg or 13.7 kg/ha; it ranged from 0. 6 to 28.8 kg/ha. Gill nets of 102-mm-bar mesh were optimum for harvest. Mea n harvest weights were significantly different among reservoirs. A positive correlation was found between relative growth and mean total alkalinity me asured during the April-October growth season. Relative growth was also pos itively correlated with mean sample site depth and conductivity measured du ring the growth season. The mean harvest weight was negatively correlated w ith photic zone depth. Paddlefish growth was lower in reservoirs infested w ith macrophytes during the growth season, and condition factors at harvest were significantly different among some reservoirs. Our results indicated t hat reservoir ranching is a viable method for producing market-size paddlef ish within the limits set by reservoir fertility. We conclude that PIT tags are not suitable for paddlefish when implanted in the body cavity. There w as no evidence that paddlefish grazing at the densities that were realized adversely affected existing reservoir ecosystems.