Short term preservation of spermatozoa of rainbow trout (Oncorhynchus mykiss)

Short term preservation of spermatozoa of salmonid fishes for practical use, increasing of reproduction potentials and reducing of expenses, has an important role in hatcheries. In this study spermatozoan motility and fertilization rate of 29 commercially cultured rainbow trout were examined. Semen was collected by abdominal stripping at the volume of 4.49±1 (mean±SD) ml and sperm concentration was determined by heamocytometer following 1:600 dilution with saline solution (0.9% NaCl). To find the effects of preservation time on fertilization capacity, samples were diluted with extender (Glucose 54gL-1, Tris 0.5gL-1, DMSO 9%, Egg yolk 20%) and held at 3 different cool conditions: room temperature (+15°C), refrigerator (+5°C) and crashed ice (+ 1-2°C) and sperm motility followed up each 30 mins until complete ceasation. Fertilization, hatching and larval stage rate were determined after 24, 48 and 72 hours. Results showed that the motility of sperm samples held at 15 °C and 5°C were completely ceased after 2 and 24 hours respectively. However it lasted up to 144 hours at1-2°C.Fertilization, hatching and larval stage rates of sperm samples hold at 1- 2°C were 68.45%, 62.1% and 58.2% (after 24 hours), 53.2%, 43.2% and 40.9% (after 48 hours) and 36.6%, 31.6% and 23.7% after 72 hours, respectively, and all showed a significant decrease compared with control (90.32%, 83.27% and 81.12% respectively). Comparing the results showed that holding samples in test tubes at 1-2°C is the best method for short term storage of rainbow trout spermatozoa.