Evaluation of Treatments for Induction of Ovulation in Northern Pike (Esox lucius L.)

摘要

Various induction protocols were compared with the aim to reach ovulation in northern pike (Esox lucius L.). The effectiveness of salmon D-Arg6Pro9NEt-GnRHa at two doses in combination with various additives were tested: 50 and 100 μg kg-1 (groups GnRHa 1 and 2), GnRHa at 50 and 100 μg kg-1 in combination with 8 mg kg-1 metoclopramide (groups 3 and 4), GnRHa at 50 and 100 μg kg-1 emulsified in Freund′s incomplete adjuvant (FIA) (groups 5 and 6), and GnRHa at 50 and 100 μg kg-1 emulsified with FIA 8 mg kg-1 and metoclopramide (groups GnRHa 7 and 8). These treatments were compared to indoor controlled conditions (Group ICC, injected with saline solution, without hormonal treatment) and two traditional treatments: 3 mg kg-1 carp pituitary (Group CP) and ambient outdoor conditions (Group AOC, injected with saline solution only, without hormonal treatment). All fish in Group CP and 70% of those in Group AOC ovulated. The latency periods for Group CP was 96 ± 4 h and 264±58 h for Group AOC. One Group-3 female ovulated spontaneously 108 h post-injection, whereas none of the other GnRHa injected or Group ICC fish ovulated. The pseudogonadosomatic index was 19.3±5.9%; 18.5% and 17.8±7.5% in the AOC, Group 3 and CP, respectively. The fertilization rate reached 88.6±4.5%; 85.5±12.0% and 66.0±13.7% in AOC, Group 3 and CP, respectively. The hatching rate was 68.6±9.9%; 65.5±7.5% and 54.4±8.0% in AOC, Group 3 and CP, respectively. The ovarian fluid pH was significantly higher (8.27±0.03) in AOC compared to CP group (8.11±0.02) (P>0.05). Ovarian fluid of the spontaneously ovulated Group-3 fish had a pH of 8.35. There were no significant differences in egg size and weight among successfully reproduced groups – AOC and CP (P>0.05).