Effects of successive milt collections on sperm quality and reproduction in wild and cultured endangered Caspian brown trout, Salmo trutta

In the present study, the effect of successive milt collections on spermatological parameters and reproduction efficiency in wild and cultured endangered Caspian brown trout was investigated. The milt collections were done 3 times at two week intervals. After milt collection, a small amount of milt was allocated for milt quality evaluation and the reminder was used for fertilization. Based on the results obtained, in the wild fish samples, the values of fertilization rate, eyeing rate, hatching rate, milt volume and duration of sperm motility decreased during successive stripping (p<0.05) while results for spermatocrit, and sperm density did not show significant differences (p>0.05). Also, the percentage of abnormal spermatozoa increased during successive stripping in the wild fish (p<0.05). The survival rate of larvae did not show significant changes during successive strippings (p>0.05). In cultured fish, similar results were found for fertilization rate, milt volume and duration of sperm motility (p<0.05), although the eyeing rate, hatching rate, spermatocrit and sperm density values did not show significant changes during successive strippings (p>0.05). Also, the survival rates of larvae were statistically different between the second and third strippings (p<0.05). In conclusion, our results showed that successive milt collections have a significant influence on milt quality and reproductive efficiency in male Caspian brown trout, with the best milt being available in the first stripping.