Biochemical characterization of Siberian sturgeon Acipenser baeri and sterlet Acipenser ruthenus milt plasma and spermatozoa

This paper provides data concerning biochemical composition of milt of two sturgeon species, Siberian sturgeon bred in aquaculture facility of Inland Fisheries Institute in North Poland and sterlet (from two different populations from Danube and Odra). Milt plasma of Siberian sturgeon and sterlet, when compared to teleost fish, is characterized by much lower osmolality (up 70 to 96 mOsm kg⁻¹) and protein concentration (0.24–0.58 g l⁻¹). In spite of the presence of an acrosome and acrosin the antiproteinase activity of seminal plasma was low (12.79–25.40 U l⁻¹). Activities of arylsulfatase and β-N-acetylglucosaminidase were found in spermatozoa. This agrees with the presence of an acrosome in sturgeons sperm. Similarly to mammals, these enzymes are also present in milt plasma. We determined a range of enzymatic activities from the minimal (seminal plasma) to the maximal damage (supernatants obtained after freezing-thawing without cryoprotectant). Activities of arylsulfatase, β-N-acetylglucosaminidase, lactic dehydrogenase and acid phosphatase were released from spermatozoa after freezing-thawing. For this reason they are good potential candidates as a markers of cryoinjury to sperm acrosome and midpiece. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of fish and rapeseed oils on growth performance,egg fatty acid composition and offspring quality of sterlet sturgeon (Acipenser ruthenus)

The aim of this study was to evaluate the long‐term effects (7‐month experiment) of diets consisting of fish oil (Kilka fish) and vegetable oil (rapeseed) on the reproductive performance of sterlet sturgeon (Acipenser ruthenus) broodstock. Forty‐five broodstock (990.3 ± 20.05 g) were randomly allocated to three different diet treatments. Three experimental diets were formulated with graded levels of fish oil (100% FO), vegetable oil (100% VO), and a combination of fish and vegetable oil (50% FO + 50% VO). At the end of the 7‐month feeding trial period, the weight gain and final weight were changed significantly different between the treatments (p < 0.05). Broodstock fed the FO + VO diet had higher growth than those fed the only FO or VO diets (p < 0.05). The highest germinal vesicle migration percentage was observed in FO + VO treatment (p < 0.05). The DHA/EPA, DHA/ARA and EPA/ARA ratios in oocyte exhibited a significant difference in the different treatments (p < 0.05). This study indicates that nutrition of broodstock with diet including FO + VO (p < 0.05) can positively affect the growth performance of larvae compared with only FO or VO diets. Furthermore, the high levels of 18:1n‐9, AL and ALA contents in oocytes from broodstock fed VO and the lowest ALA content in oocytes from broodstock fed FO underlined the important role of broodstock diets in the reproductive process and embryonic and/or larval developments of sterlet.     

小体鲟在静水池塘中生长观察

本试验利用西泉眼水库岸边静水池塘养殖开口进食已两周的小体鲟幼鱼,其体质量和体长分别为0.125±0.95g、2.98±1.72 cm;经过4周饲喂,其育成率达到70%以上;体长为6±2.98cm、体质量1.78±1.25g;体长、体质量增长分别为0.115cm/d、0.0595g/d.试验结果证实如配合采用调整养殖密度、配套养殖设施、清理天敌并在池塘周围建围栏、调节水质、越冬并搭配不同食性、不同水层的鱼种等措施,小体鲟是适于在北方静水池塘生长的.     

Bayesian modelling suggests that the sterlet (Acipenser ruthenus,Linnaeus 1758) population is ageing in the middle Danube River

1. In the past, sturgeons played an important role in commercial and recreational fisheries in the Danube River and its tributaries. Human impacts in the Danube River Basin coupled with exploitation of sturgeon stocks led to all species being either locally extinct, critically endangered or of unknown status.
2. Sterlet (Acipenser ruthenus, Linnaeus 1758) is the last known sturgeon species occurring in the upper and middle Danube; however, the population of this species is considered unbalanced and decreasing since the beginning of the twenty-first century.
3. The decline of sturgeon stocks has been noted before owing to their economic importance. With commercial fisheries being forbidden in the Slovak section of the Danube River, there is generally no information available about the status of what is considered a local population.
4. Databases containing recreational catch of sterlet (2003–2018) and historical records of commercial harvest (1961–1990) were used to describe the trend in the weight and number of sterlet caught over the following years.
5. Modelling indicated that the number of fish caught each year appears to be lower, while the average weight of each individual is increasing. This might suggest that the population is ageing.
6. Although older individuals can contribute a great deal more to spawning because they produce a greater number of eggs, several problems are apparent. The number of spawners might be decreasing as a result of bycatch or fishing, their ability to spawn might be obstructed, or annual recruitment may fail owing to unpredictable events.
7. Although restocking programmes are in place to help maintain the sterlet population in the Danube River, their efficiency seems to be drastically low. In fact, restocking could be of little value unless studies on the availability of key habitats are conducted and their protection and restoration are ensured.

     

Studies on the semen biology and sperm cryopreservation in the sterlet, Acipenser ruthenus L.

The present study investigated motility, acrosome reaction, fertility and cryobiological parameters of the semen of the sterlet, Acipenser ruthenus L. Sperm motility persisted for about 4 min in water, and the main swimming type was the linear motion. Motility was prolonged at osmolalities of 12.5 mosmol kg^?1 and in the presence of magnesium ions, while calcium had no effect. Also a pH in the range of 7.0–9.0 had no effect on ` motility. At osmolalities of 25–50 mosmol kg^?1 the sperm motility was partly inhibited, at osmolalities of 100 mosmol kg^?1, completely and irreversibly. In 50 mosmol kg^?1 solutions with 2.5–5 mM L^?1 KCl the motility inhibition was total, but reversible. The acrosome reaction was not induced by one of the described solutions, but the percentage of spermatozoa with reacted acrosomes was low (<20%) and highly variable in all experiments. The optimal extender base for cryopreservation was a solution consisting of 50 mM L^?1 NaCl, 5 mM L^?1 KCl, 10 mM L^?1 Tris (pH 8.5). From the tested cryoprotectants only dimethylsulphoxide (DMSO) and methanol provided sufficient cryoprotection. After freezing and thawing, the motility rates and swimming velocities were higher with DMSO than with methanol. However, the fertility was very significantly reduced with DMSO (10.3±0.5%) while with methanol fertilization rates in a similar range (32.7±4.4%) as with fresh semen (33.90±0.8%) could be obtained. Optimal freezing conditions for sterlet semen were in the vapour of liquid nitrogen 3–5 cm (?95°C to ?85°C) above its surface, the optimal thawing conditions at 25°C for 30 s. The acrosome reaction was not induced by these cryopreservation protocols.     

Impact of feed ration on growth and the results of sterlet,Acipenser ruthenus L., artificial reproduction

In the study the effects of artificial reproduction of sterlet (Acipenser ruthenus) fed different feed ration were compared. Three doses of feed were used: 1.0%, 0.75% and 0.5% of the fish biomass per day. The results indicate that the feed rations for fish used for caviar production or breeding material should differ. The optimal ration for the quality of sex products and progeny was 0.75% of the fish biomass, whereas in view of the number of maturing fish, the better ration was that of 1% of the fish biomass. In group fed 0.75% of the fish biomass per day the highest GSI value, the largest eggs and hatch and the highest survival to the hatch were noted. The feed ration of 0.5% of the fish biomass was too low, as indicated by the low parameters of eggs obtained, their survival and the smallest number of mature and ovulating females. These results can provide direction for the creation and exploitation of spawner stocks as well as for other sturgeon species cultured under controlled conditions.     

Effects of background colour on growth indices and stress of young sterlet (Acipenser ruthenus) in a closed circulated system

In this study, the physiological response and growth performances of Acipenser ruthenus were investigated after a long‐term background colour adaptation (12 weeks). Twelve groups of 10 individuals with initial mean body weight of 183 g were reared in black, dark blue, grey and white tanks (three replicates for each colour). At the end of the experiments, growth (initial body weight, final body weight, weight gain per cent, food efficiency ratio, protein efficiency ratio, specific growth rate), blood (cortisol, glucose, pO_2, pCO₂, pH, haematocrit, osmolality, triglycerides, cholesterol, total lipids) and liver (hepatosomatic index, total lipids, glycogen) parameters were analyzed. Plasma cortisol in the dark‐adapted sterlet (21.95 ± 3.9 ng mL^?1) was significantly lower than those in white‐adapted fish (39.44 ± 6.5 ng mL^?1), whereas there were no significant differences in cortisol levels between the grey‐adapted fish (23.05 ± 4.1 ng mL^?1) and dark blue‐adapted fish (24.2 ± 3.6 ng mL^?1). A remarkable increase in mean of body weight (%) was detected in dark‐adapted sterlet (45.2 ± 3.2) being 27.67%, 12.1% and 11.8% higher than the white, grey and dark blue‐adapted fish respectively. The obtained results verified that different background colours lead to different growth performances and physiological responses of starlet, depending on rearing conditions.     

史氏鲟及小体鲟不同组织中溶菌酶水平的比较

对史氏鲟及小体鲟血清和几种主要组织的溶菌酶含量进行了测定和比较后发现,同小体鲟相比,史氏鲟的血清、鳃、肝、胃、前肠及后肠的溶菌酶量均较高,血清之间有极显著的差异,鳃、肝及后肠均有显著性的差别,胃及前肠之间无差异;小体鲟的粘液、幽门垂及脾中的溶菌酶含量较史氏鲟高,但无显著性差异,由此可见,虽然同为鲟科鲟属,溶菌酶在两种鱼之间的差别还是很显著的。     

Using machine learning algorithms to analyse the scute structure and sex identification of sterlet Acipenser ruthenus (Acipenseridae)

Sturgeons are valued as specialty black caviar, which is very expensive. Only females are used in the technology of caviar aquaculture. Universal method of sex determination has not yet been developed. Most of known methods are not sufficiently accurate, or used at a relatively late age, or difficult to use. Perfect early determination of sex is considered to be impossible. Because of the dark colour of most sturgeons and important morphological differences, which fish of almost all ages have, were overlooked. We first found that the scute structure of sterlet sturgeon depends on the sex. The found dependencies with the help of machine learning algorithms open a possibility for creation of sex determination equipment using the artificial intelligence. Our results open a perspective for creation of sex determination methods for other 23 sturgeon species, which can increase the efficiency of caviar aquaculture and restoration of sturgeons in natural waters.