|
|
Optimalizace reprodukce a kvality gamet u okounovitých ryb
KŘIŠŤAN, Jiří
Pond and intensive aquaculture of percids relies mainly on juveniles supplied by semi-artificial and artificial reproduction. Fish hatcheries do not always provide optimal conditions for percid reproduction. This project was undertaken to optimize reproduction methods of Eurasian perch (Perca fluviatilis L.) and pikeperch (Sander lucioperca L.). Reproduction parameters were compared in farmed and pond-reared perch broodstock without hormone treatment. Spawning was successful without hormone induction at 92.3% and 76.9% in farmed and pond-reared perch, respectively. Significant differences in morphological characteristics (gonadosomatic, hepatosomatic and viscerosomatic indices), fecundity, hatching, and post-spawning mortality were detected. All results, with the exception of spawning success and post-spawning mortality, were superior in pond reared broodstock. Further studies are required to optimize protocols for using better artificial food in farmed perch and decreased stress and post-spawning mortalities in pond reared perch broodstock. The possibilities of using clove oil, Propiscin, or 2-phenoxyethanol as an alternative to tricaine methane sulphonate (MS222) as anaesthetic, particularly with respect to reducing fish stress, were investigated. The haematological and biochemical profiles of pikeperch anaesthetized with clove oil (33 mg l?1), Propiscin (1.5 ml l?1), 2-phenoxyethanol (0.3 ml l?1), and MS222 (150 mg l?1) were determined. Each tested group was divided into two subgroups; the first subgroup was sampled 10 min after application and the second 24 h post-application. Clove oil was shown to be associated with the lowest effects in pikeperch, and therefore could be recommended as an alternative to MS222, while Propiscin and 2-phenoxyethanol were shown to be unsuitable for use with pikeperch. In Eurasian perch the use of semi-artificial reproduction for mass production of embryos was shown to be simpler and more effective. With mass incubation, 1 134 000 embryos (59% of total production) were obtained with a semi-artificial spawning regime and 796 000 embryos (41% of total production) with artificial spawning. Based on these results, we can recommend the semi-artificial spawning for production of perch embryos. Differing doses of two commonly used hormone preparations: human chorionic gonadotropin (hCG) and mammalian GnRHa (Supergestran) were tested for induction of ovulation in pikeperch. A broad range of effective doses is used in aquaculture of pikeperch. The minimal effective dose based on ovulation success is still missing. Hormone therapy applied to excess can result a detrimental impacts on broodstock fecundity and quality of eggs. Results indicated that a single injection of hCG or Supergestran could be used for successful ovulation, while no spawning was observed in a control group treated by saline solution. Among hormone treated groups, the best results were observed in groups treated with hCG at 500 and 750 IU kg-1 BW and in groups treated with mGnRHa at 25 ?g kg-1 BW. The sperm of pikeperch and Eurasian perch show similar morphology and fine structure, with the exception of differences in arrangement of midpiece and centrioles and the presence of a fin-like structure on the flagellum in pikeperch. Our results suggest use of an activation medium containing Ca2+ for activation of short-term stored sperm. Efficacy of five concentrations of Alcalase enzyme for elimination of egg stickiness compared to a milk/talc suspension was determined. Results indicated that 0.5-2.0 ml l-1 of Alcalase for 2 min may increase pikeperch egg hatching success (80-85%) compared to the milk-talc suspension. The highest hatching rate (85.4%) was observed with 1.5 ml l-1 of Alcalase. The application of Alcalase successfully eliminated pikeperch egg stickiness in 2 min compared to 60 min with traditional milk/clay/talc methods.
|
guest ::
RSS feed.