Rearing paddlefish Polyodon spathula to maturity in ponds in the Republic of Moldavia

Abstract

Juvenile paddlefish (Polyodon spathula) hatched in 1988 have been cultivated in ponds up to sexual maturity (age 11+) in Moldavia, located in central European Plain with an altitude ranging from 429.5 m to 147 m. The average annual air temperature is 9.5-10 °C and the growing season for pond fish is 180 to 210 days The first summer the fish were reared under either mono- or polyculture conditions starting at an initial stocking density of 10000 and 5000 fish ha 1 . By the autumn the individual weights were 72 and 139 g and the survival rate 48 and 63%. respectively. In subsequent years the paddlefish were associated in ponds with various sturgeon species. A polyculture experiment associating the sturgeon, Acipenser baeri (density 4300 ind. ha ) and paddlefish (density of 8300 ind. ha 1 ) yielded respectively 59% survival and 432 kg ha 1 productivity for Polyodon and 77% survival and 174 kg ha productivity for A. baeri. By the third year (2 + ) the paddlefish reached average weight of 1.5-2..5 kg and their final survival and productivity values were 50-70% and 150-463 kg ha - 1 . respectively. Males (6-7 kg) matured at the age of 5 + -6 + . Females rached sub-final stage IV at the age of 11+ + (30%) or 12 + (70%) and a weight of 10-16 kg with spawning and production of viable fry. Caviar was made from the roe of these females. In I + - 3 + aged firsh, the proportion of flesh and skin was stable at 54-57% while the proportion of head decreased from 44% at 0 + to 26% at 3 + .