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Two stocks of Baltic sturgeon (Acipenser oxyrinchus oxyrinchus) were cultured under different conditions. Initially, the first group was held in an earthen pond without water flow, and after three years It was moved to a tank in a closed recirculating system. The second group was cultured throughout the study period in a flow-though trout pond. Both groups were fed similarly. Fish growth in the earthen pond was unsatisfactory, and fish condition decreased, but the annual mean body mass increases in the flow-through pond ranged from 30 to 40%. After moving the first group of fish to the tank, the poor growth was compensated for and by the end of the 2011 the mean body mass of these fish exceeded the mean of that in the other group. The results of gonad maturity tests performed in the final phase of the study indicated there were maturing males in both groups of fish.
Work to restore the Baltic sturgeon was begun in Poland in 2004. The initial material has comprised mainly fertilized Atlantic sturgeon eggs imported annually from Canada. The aim of the current study was to use to perform genetic analyses based on 16 microsatellite loci of Atlantic sturgeon wild spawners used in artificial reproduction and breeding in 2011. These results were compared to those of previous analyses of individual Atlantic sturgeon bred for the restoration of this species in Poland and to individuals from the founder population from the Saint John River. The analysis of polymorphism indicated that the genetic variation of the 2011 fry was similar to that observed in previous years. It was confirmed that groups of 2011 fry, designated as 1 and 2, originated from two different females. The group 1 fry were the progeny of one female and three males, while those in group 2 were the progeny of one female and two males. The reproductive success of the males was not equal, and in both instances the same male dominated. Some of the individuals used in breeding were related, which can produce negative inbreeding impacts in the progeny of these pairs. In the interests of building a future broodstock from the year class analyzed in this study, it would be optimal to identify individuals that originate from each pairing in equal numbers.
The population of the Atlantic Baltic sturgeon, Acipenser oxyrinchus, occurring in the Baltic Sea was recognized as extirpated in the mid twentieth century. Since 2004, work has been underway in Poland to restore the Baltic sturgeon species. The material used in this project comprises fertilized eggs and hatch obtained from Atlantic sturgeon spawners from the St. John River and imported from Canada. The aim of the ichthyological work being done as part of this project is to rear stocking material and create a broodstock under aquaculture conditions. In the 2006-2013 period, approximately 766,300 fry individuals with mean weights ranging from of 5-9 to 1500 -2500 g were released into Polish rivers. The goal of these pilot stocking programs was to study migration routes and the behavior of the fry in the rivers. The oldest individuals in select stocks are beginning to mature. Stocking has been expanded in recent years to include Neman and Pregola river tributaries. A further consequence of stocking and expanding areas that are stocked to include all of the historic sturgeon rivers in the Baltic Sea basin, in the opinion of the authors, should lead to the restoration of the Baltic sturgeon population.
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