Comparison of growth performance and smoltification of triploid and diploid black sea trout (salmo labrax) in freshwater and seawater

Abstract

This study aimed to evaluate the growth performance and smoltification process of triploid Black Sea trout, produced using the pressure shock method. Length, weight, survival rate (SR), specific growth rate (SGR), condition factor (CF), feed conversion rate (FCR), haematological parameters (WBC, LYM, MID, GRAN, RBC, HGB, HCT, MCV, MCH, MCH, MCHC, PLT, MPV, PDW), stress responses (cortisol and glucose values), osmoregulatory capacity indicators, Ca, Cl, Na, and K levels in blood serum were examined. The triploid groups showed higher length, weight and specific growth rate in both freshwater and seawater with a salinity of 18 ‰ (P<0.05). After a 90-day growth period, the best growth performance was seen in triploid freshwater group with the mean initial lenght of 13.60±0.06 cm and weight of 26.60±0.45 g. The final length, weight and specific growth rate of this group were 22.10±0.21 cm, 139.32±3.35 g and 1.84±0.13, respectively. Temporal changes in blood Ca, Cl, Na, and K ion levels in blood, cortisol and glucose levels showed that the adaptation ability of triploid fish to seawater might be different from that of diploids. The cortisol values of triploid groups were lower than that of diploid groups in freshwater but higher in seawater, while glucose values showed fluctuations between groups during the whole study period (P<0.05). Ca reached the highest values in triploid freshwater group on day 17, Cl in diploid and triploid seawater groups on day 24 and Na in triploid seawater group on day 17 (P<0.05). K value showed no statistical difference between the groups throughout the study. Understanding the physiological and biological responses of fish to environmental changes during seawater transition and adaptation is expected to enhance the survival and growth performance of diploid and triploid Black Sea trout.