Effects of different stripping methods of female and activation medium on fertilization success in northern pike (Esox lucius)

In this study, the quality of northern pike eggs collected by the traditional method (hand stripping) and the pneumatic method (air stripping) was compared. Additionally, different activation solutions (Billard solution, hatchery water, and Woynarovich solution) were tested for their effects on egg fertilization under artificial conditions. After the eggs were collected, the Pseudo-Gonado-Somatic Index (PGSI) was measured. Although the values of the PGSI in the samples obtained with use of air stripping were lower (13.8 ± 3.9%), they did not differ statistically from those obtained by hand stripping (16.5 ± 5.4%). Hatchery water and Woynarovich solution were found to be the most suitable solutions for sperm activation using the Computer-Assisted Sperm Analysis (CASA) system as compared to the Billard solution. Hand stripping was found to negatively affect the percentage of fertilized eggs and the percentage of hatched larvae in samples fertilized in hatchery water and Woynarovich solution. When the traditional method of egg collection was used, there were no differences in the percentage of fertilization and the percentage of hatched larvae between Billard solution (54.0 ± 21.5% and 44.1 ± 21.9%, respectively), hatchery water (60.0 ± 22.5% and 55.9 ± 22.8%, respectively), and Woynarovich solution (72.0 ± 25.8% and 69.0 ± 23.9%, respectively) treatments. Air stripped eggs showed a higher fertilization rate when hatchery water or Woynarovich solution was applied (86.2 ± 9.3% and 92.4 ± 3.9%, respectively). Also hatching rate was the highest in these samples (83.0 ± 8.4% and 88.3 ± 6.2%). The application of the pneumatic method and Woynarovich solution to northern pike artificial fertilization resulted in higher fertilization and hatching rates as compared to other techniques. Because this was successful in northern pike, the use of air stripping is a promising option for artificial reproduction in other fish species.