Polyploidy in sturgeons makes them highly susceptible to interspecific hybridization, and these interspecific hybrids have been described in nature as well as in captivity. Nevertheless, the fitness-related traits between sturgeon hybrids and pure species have been poorly compared as yet. In the present study, we compared the reproductive parameters such as fertilization rate and hatching rate, growth traits and genetic polymorphism in the artificially produced hybrids of the Siberian sturgeon (Acipenser baerii) and Russian sturgeon (A. gueldenstaedtii) with their purebreds. Fertilization and hatching rates were found to be significantly higher in Siberian sturgeon (♀) × Russian sturgeon (♂) hybrid group compared to purebreds. The highest cumulative survival rate was determined in purebred groups until 151 days post-hatch (dph); however, this trend changed and Russian sturgeon purebred showed the lowest cumulative survival rate (0.21%) by 913 dph. Similarly, the lowest average body weight was recorded in Russian sturgeon purebred group (264 g). In contrast, the highest average body weight was recorded in Russian sturgeon (♀) × Siberian sturgeon (♂) hybrids (435.3 g) and the highest cumulative survival rate was recorded in Siberian sturgeon (♀) × Russian sturgeon (♂) hybrids (12.32%) by 913 dph. No significant differences were found at heterozygosity levels among studied crosses. Our results showed that studied sturgeon hybrids had higher survival and growth if compared with the purebreds under provided hatchery conditions.

The aim of the present study was to estimate and compare the growth and survival traits of the hybrids and purebreds produced by crossing the Siberian sturgeon (Acipenser baerii) (S) and sterlet (Acipenser ruthenus) (St) in order to determine the heterosis effect in the F1 generation. We compared the breeding conditions, mean body weight (BW) and cumulative survival in the artificially produced hybrid crosses of sterlet and Siberian sturgeon with respect to their pure parental species in indoor and outdoor aquaculture systems at different developmental stages. Fertilization and hatching rates were found to be significantly higher in S × S purebred compared to St × S hybrid. The highest values of BW were recorded in St × S hybrid (557.54 ± 179.7 g) on 862 days post-hatch (dph) while the highest cumulative survival was recorded in S × S purebred (14.3%). The recorded cumulative survival and mean BW was significantly lower in St × St purebred. The highest positive heterosis was recorded for mean BW of St × S hybrid (51.3% on 862 dph) throughout the sampling points. The studied sturgeon hybrids had higher mean BW compared to St × St purebred under suboptimal rearing conditions. Although there was no clear demonstration of the superiority in performance of reciprocal hybrids over purebreds, the St × S hybrid can be used for achieving better productivity in aquaculture systems. How to cite this article: Shivaramu S, Vuong DT, Havelka M, Lebeda I, Kašpar V, Flajšhans M. The heterosis estimates for growth and survival traits in sterlet and Siberian sturgeon purebreds and hybrids.

The present study aimed to investigate and compare fitness-related traits and ploidy levels of purebreds and hybrids produced from sturgeon broodstock with both normal and abnormal ploidy levels. We used diploid Acipenser ruthenus and tetraploid A. baerii males and females to produce purebreds and reciprocal hybrids of normal ploidy levels. Likewise, we used diploid A. ruthenus and tetraploid A. baerii females mated to pentaploid and hexaploid A. baerii males to produce hybrids of abnormal ploidy levels. Fertilization of ova of A. ruthenus and A. baerii of normal ploidy with the sperm of pentaploid and hexaploid A. baerii produced fully viable progeny with ploidy levels that were intermediate between those of the parents as was also found in crosses of purebreds and reciprocal hybrids of normal ploidy levels. The A. ruthenus × pentaploid A. baerii and A. ruthenus × hexaploid A. baerii hybrids did not survive after 22 days post-hatch (dph). Mean body weight and cumulative survival were periodically checked at seven-time intervals. The recorded values of mean body weight were significantly higher in A. baerii × pentaploid A. baerii hybrids than other groups at three sampling points (160, 252 and 330 dph). In contrast, the highest cumulative survival was observed in A. baerii × A. ruthenus hybrids at all sampling points (14.47 ± 5.70 at 497 dph). Overall, most of the studied sturgeon hybrids displayed higher mean BW and cumulative survival compared to the purebreds. The utilization of sturgeon hybrids should be restricted to aquaculture purposes because they can pose a significant genetic threat to native populations through ecological interactions.