Przeżywalność i wzrost narybku troci wędrownej (Salmo trutta m. trutta L.) uzyskanego z mrożonego nasienia

The cryopreservation of milt in liquid nitrogen has recently been introduced on farms as a storage technique for the milt of valuable breeding lines and for surpluses of spermatozoa. It is also used in conservation programs for endangered species. However, physical factors and the chemical environment during the freezing of gametes in liquid nitrogen can damage the cells, which can result in changes in cell properties and can also affect the characteristics of the offspring obtained from fertilization with frozen gametes. The resulting defects can appear at different stages of ontogenesis and influence life functions. The aim of this study was to evaluate the survival and health of sea trout offspring up to the three-month-old alevin stage. The offspring were obtained by fertilizing fresh eggs using spermatozoa that had previously been frozen in liquid nitrogen with the addition of methanol as a cryoprotectant. The milt was frozen in straws in liquid nitrogen according to the standard technique for salmonids. Then the eggs were fertilized with fresh (control group) and frozen/thawed (experimental group) sperm. The eggs were incubated, and then the fish were reared until the age of three months in a closed recirculation system. During early development, no significant differences between the control and experimental groups of fish were noted. Survival from the eyed-egg stage to the end of rearing was similar in both groups. The weights of the hatched and 3-month-old alevins were similar. These results suggest it is possible to use frozen milt for fry production and fish population restoration. Moreover, the results indicate the need for further research on monitoring the development of offspring produced through fertilization with frozen sperm.