Management of paddlefish fry and juveniles in Bulgarian conditions

Abstract

When paddlefish larvae were reared in tanks and fed on zooplankton, a length of 12-15 cm and a weight of 9.2 g had been obtained by the second month after hatching. After a further 2-months of pond rearing, the survival rate was 48%, and the juveniles had reached an average weight of 27.74 g and length of 22.5 cm. Much better growth rate was achieved when both paddlefish fry and juveniles were reared only on artificial food in tanks. At the end of the first month, a weight of 11.6 g had been reached; at the second month the paddlefish weight was 33.29 g, at the third month it was 60.2 g, and at the fourth month it was 127.7 g. There were two cases in which, respectively, 1,000 and 1,500 paddlefish with an average body weight of 33-60 g were stocked in a reservoir. At the age 5 months the fish had reached, or exceeded, an average weight of 500 g, and, after 1 year, it was over 700 g, which is an indicator of the good rearing opportunities this reservoir offered.

Paddlefish ( Polyodon spathula ) in Europe: An aquaculture species and a potential invader

“…Initial imports to Europe were 5,000 hatched larvae originating from the USA (Missouri) and introduced in the USSR in 1974, with further introductions in both 1976 and 1977 (Vedrasco et al., ). Paddlefish was subsequently imported to the Moldovan SSR (now Republic of Moldova) in 1978, to Hungary in 1986, to Germany in 1987, to Austria in 1990, to Romania and Slovakia in 1992, to Czech Republic and Poland in 1995, to Greece in 1997, to Belarus in 2001, and to Bulgaria in 2003 (Vedrasco et al., ; Holčík, , ; Hubenova et al., ; Kottelat & Freyhof, ; Uzunova & Zlatanova, ; Nowak, Szczerbik, Tatoj, & Popek, ; Koščo, Košuthová, Košuth, & Pekárik, ; Lusk, Lusková, & Hanel, ; Mastitsky, Karatayev, Burlakova, & Adamovich, ; Musil, Jurajda, Adámek, Horký, & Slavík, ; Mims & Shelton, ; DAISIE, ; Perdikaris et al., ; Appendix ). According to survey respondents, paddlefish aquaculture is absent from the UK, Ireland, France, Spain, Portugal, Italy, Switzerland, Albania, Macedonia, Montenegro, Netherlands, Serbia, Bosnia and Hercegovina, Sweden, Norway, Finland, Lithuania and Estonia.…”

“…Paddlefish was imported with the aim to be reared in carp pond farms, motivated by its characteristics as a warm water species, filter feeder and economically valuable fish, which is able to adapt to conditions of intensive culture and reduce the amount of zooplankton in ponds (Musil et al., ; Nowak et al., ). The interest by European aquaculture was driven mainly by the high growth rate of paddlefish, the supplemental utilization of natural feed, potential for polyculture, and the potential of producing black caviar (Hubenova et al., ). The species was considered a good candidate for polyculture, as a complement to or even substitution for the less valuable carps (Lobchenko et al., ; Vedrasco et al., ).…”

“…According to Kolman (2000 as cited in Nowak et al., ), in Poland it was an aquaculture species of rather low interest, although it was stocked in some farms, while Grabowska, Kotusz, and Witkowski () reported that it is cultivated in Poland in many fish farms and privately owned recreational “put‐and‐take” waters for anglers. In Bulgaria, paddlefish is reared in regions of Plovdiv and Vidin (Hubenova et al., ). In the Russian Volga Delta, paddlefish was also reared to commercial size for meat production (Lobchenko et al., ).…”

“…As outlined above, the main challenges faced by paddlefish aquaculture in Europe are related to the rearing of stocking material, which suffered from considerable losses of early life phases in the rearing process over the first summer, resulting in low volumes of the produced market‐size fish (Hubenova et al., ). High broodstock mortality of unknown reasons sometimes led to the eradication of stocks, which occurred in Ukraine and Bulgaria (Mims & Shelton, ).…”

“…Paddlefish was first introduced to Europe in 1974, when hatched larvae were imported from Missouri to the former USSR (Vedrasco, Lobchenko, & Billard, ). Over the following decades, paddlefish was introduced in aquaculture in additional countries throughout Europe, such as Romania, Bulgaria, Hungary, Austria and Germany (Arndt, Gessner, & Raymakers, ; Hubenova, Zaikov, & Vasileva, ; Kottelat & Freyhof, ; Lenhardt et al., ). The main motivation behind its introduction was the potential for rearing in natural polyculture ponds and large temperate reservoirs due to its planktivorous feeding (Holčík, ; Lobchenko, Vedrasco, & Billard, ).…”