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Until 1960s, vimba was found abundantly in Polish rivers and was an important species for the fishing industry. Overfishing, water pollution and dam constructions brought most of the vimba populations close to extinction. We analyzed the genetic variability of several remnant vimba populations in the Vistula and Oder river basins. The 305-bp fragment encompassing the 5′-end of the mtDNA control region was sequenced in a total of 202 wild specimens derived from six populations. Six different haplotypes were distinguished. The population of Barycz River was found to be the most polymorphic and was chosen as a source of breeding material for the vimba restitution program. In the years 2000-2008 fishes from this river were caught, spawned in captivity and released to the same river. The number of fishes returning to the Barycz River spawning grounds was monitored in the following years. In 2008, it was almost 70 times higher than the number of fishes recorded in 2003, when the lowest population size was observed. The haplotype and nucleotide diversities of the restored population were similar to those of the original population. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine gonadal maturity in male and female vimba after induced spawning in the years 2001 throughout 2004, based on spawners derived from an anadromous population obtained from the Barycz River. For these 4 years, fry derived from each successive spawning were raised in carp ponds at the Experimental Hatchery Centre of the Polish Angling Association in Szczodre, Poland. In February 2005, gonads were collected from males and females and their maturity determined after histological preparations. Additionally, in females the diameters of oocytes undergoing trophoplasmic growth were determined and compared. Histological analysis showed that all females had gonads at maturity stage IV, except the youngest fish, in which maturity stage I was determined. It was also shown that the size of oocytes undergoing trophoplasmic growth was related to age: the older the females, the greater the proportion of large-diameter oocytes. In addition, some 2-year-old females had a considerable proportion of oocytes undergoing trophoplasmic growth despite being at stage IV of ovarian maturity. Among males, 2- to 4-year-olds had gonads at maturity stage III, in which the spermatogenesis process was active. One-year-old males had testes at maturity stage II, with visible spermatogonia entering meiotic divisions. When keeping vimba under pond conditions, only 2 years are needed to obtain a mature spawner from a spawning school. The older the school, the higher the probability that a greater number of spawners will enter spawning. [ABSTRACT FROM AUTHOR]