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A study on Sander lucioperca age classes to assess preference for background color was imagined. Two groups: G1 (92 days old, average weight: 6.2 ±1.6 g) and G2 (461 days and 101.7 ±27.1 g), were continuously observed for 24 hours after one day of acclimation, using 90 fish / group (30 fish / replication / 24 hours), their behavior being recorded with cam-recorders. For the study, the walls and bottom of a rectangular research tank were colored equally in: grey, light and dark blue and green. During the study, were made 216 observations / group (72 observations / replication) and were statistically analyzed using Duncan test, with a confidence level of P˂ 0.05 or lower. Results revealed that a significant number from G1 was located on the green space, in order, preferred background color being: green, grey, dark and light blue. The G2 group expressed also high affinity for the green color (P< 0.001) concluding that, green background can give a safety feeling to the pikeperch, thus, rearing or transport of pikeperch categories in green tanks could have the benefit of stress decreasing and added benefit for this fish species in the aim of advancing the Recirculating Aquaculture Systems.

The alarming decline in sturgeon populations doubled by growing demands for sturgeon products, urge us to prevent the loss of these species. Fish stocking in natural habitats and developing fish farms are viable solutions, which can be successfully implemented with the help of reproductive biotechnologies. Despite the fact that semen cryopreservation is admittedly an important step for saving the Russian sturgeon, a reproducible standard method with good results has yet to be identified. Sperm quality assessment is essential for quantifying the impact of cryopreservation on spermatozoa. The purpose of our study was to provide additional information regarding semen cryopreservation and semen quality evaluation for the Russian sturgeon. Our study method is based on the use of two yolk-free extenders (with different cryoprotectants: DMSO and methanol) for freezing semen, using a simple freezing protocol. Parameters such as volume, concentration, motility, morphology and membrane integrity were evaluated. In conclusion, cryopreservation of Russian sturgeon spermatozoa using an extender containing methanol as cryoprotectant led to high egg fertilization percentages (72.67 ± 5.4%) even if the total motility values recorded for thawed semen were quite low (18–25%). Additionally, we identified two optimal stains for morphological studies and morphometry (Spermac stain kit and Trypan Blue Solution).

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