Katarzyna Palińska-Żarska

The type of spawning agent affects the egg composition during out-of-season spawning but not during in-season spawning in Eurasian perch, Perca fluviatilis

The aim of the study was to verify the effect of various hormonal agents [human chorionic gonadotropin (hCG) and salmon gonadoliberine analogue (sGnRHa)] applied at different stages of maturity of the females [out-of-season (maturation stage I) and in-season spawning (maturation stages II and IV)] on the proximate composition (PC) and fatty acid (FA) profile of eggs of Eurasian perch, Perca fluviatilis. The egg samples (7 samples from each group) were also collected from spontaneous spawning (without hormonal treatment) fish representing each maturation stage (I, II and IV for groups C-I, C-II and C-IV, respectively). The results were also compared with the eggs collected in nature (seven randomly chosen egg samples from natural spawning; group NS). Embryonic survival rate was recorded and analysis of PC and FA profile were performed, for all the groups. Embryonic survival rate varied among the groups, and only differences (P<0.05) between group C-I and NS were recorded. In-season spawning operation did not affect PC and FA profiles. Application of hCG or spontaneous spawning (group C-I) were found to have the highest effect on the FA profile. It concerned mostly total n-3 polyunsaturated fatty acids, but also stearic (C18:0), oleic [C18:1(cis9)], linoleic [C18:2(n-6)], arachidonic [C20:4(n-6)] and docosahexaenoic[C22:6(n-3)] acids. The application of sGnRHa during out-of-season spawning had the lowest effect on the FA profile. The results presented indicate that controlled reproduction can affect the FA profile only during out-of-season spawning. This negative effect can be presumably compensated by the application of sGnRHa as a spawning agent.

In vitro storage of unfertilized eggs of the Eurasian perch and its effect on egg viability rates and the occurrence of larval malformations.

Ova ageing is the most important factor affecting fish egg quality after ovulation. Long-term storage of fish ova, using cryopreservation and vitrification techniques, has been unsuccessful to date. Instead, short-term in vitro ova storage has been used successfully and optimized in some cultured fish species. In vitro ova storage can drastically improve mass production of larvae and juveniles in the hatcheries by providing the possibility of the synchronous artificial fertilization for different females. To study how long unfertilized eggs of Eurasian perch (Perca fluviatilis L.) can retain their fertilizing ability after stripping, eggs were stored at temperatures of 4°C, 8°C and 12°C for 72 h post-stripping (HPS). The stored eggs of four female perch were separately fertilized at 0 h (i.e. control eggs fertilized before storage) and at 6-hour intervals during the experimental period of 72 h. The embryos reaching the eyed-egg and hatched-larvae stages, eyed-egg mortality and larval malformation rates were recorded as indices of egg quality. The results indicated that the maximum eyed eggs and hatched larvae (86% and 63%, respectively) were observed for eggs fertilized immediately after stripping, whereas the storage of the eggs at 4°C for 48 HPS decreased the eyed-egg and hatched-larvae rates to 46% and 17%, respectively. The use of a higher storage temperature resulted in a more rapid decrease in egg viability: eyed-egg and hatched-larvae rates of 23% and 9%, respectively, were obtained after 48 HPS storage at 8°C and 2% and 1% for eggs stored at 12°C. Eyed-egg mortality and larval malformation rates were not significantly affected by post-stripping ova ageing for at least up to 36 h. Thereafter, both values increased significantly and were measured to be the highest in the most aged ova. The present study demonstrated that stripped Eurasian perch eggs can be stored for at least 12 h at 4°C to 12°C without a significant reduction in their quality.

The influence of inhibition of acid phosphatase, β-N-acetylglucosaminidase and lactate dehydrogenase present in the sperm of ide ( Leuciscus idus ) on the percentage of fertilised eggs

This study investigated how the inhibition of certain enzymes present in ide sperm influences sperm motility and the percentage of fertilised eggs. The enzymes studied were acid phosphatase (AcP), β-N-acetylglucosaminidase (β-NAGase) and lactate dehydrogenase (LDH). None of the inhibitors affected ide sperm motility parameters. The addition of gossypol (a LDH inhibitor) caused a considerable increase in the percentage of fertilised eggs (92-95% compared to 63% in the control). The inhibition of AcP caused a considerable decrease in fertility rate - at the highest inhibitor dose, the percentage of fertilised eggs decreased to 26%. A similar effect was seen after the addition of acetamide (a β-NAGase inhibitor), but in this case the highest dose caused complete inhibition of fertilisation. The results presented here indicate the importance of AcP and β-NAGase in the process of ide fertilisation.

Effect of urine contamination on semen quality variables in Eurasian perch Perca fluviatilis L.

The objectives of the present study were to determine values for semen quality variables in the Eurasian perch (i.e., osmolality of seminal plasma as well as sperm motility characteristics analyzed with CASA system) in response to (1) the method of milt collection (stripping or catheterization) and (2) experimental contamination of catheterized semen with urine (0%, 5%, 10%, 20%, 30% and 50% of contamination). Additionally, the effect of short-term chilled storage of experimentally contaminated semen (during the 24 h post semen collection period) on motility characteristics was investigated. Use of a typical stripping procedure resulted in about 5%-10% contamination of semen with urine, what is much less compared with other species. Markedly lesser values of straight line velocity (VSL) and consequently less linearity of spermatozoa movement (LIN) in perch semen, however, occurred as a result of stripping (46 ± 4 μm/s and 38 ± 4% for VSL and LIN, respectively), when compared to sperm collected by catheterization (87 ± 5 μm/s and 77 ± 2% for VSL and LIN, respectively), indicate that even a 10% contamination of semen with urine may have negative effects on quality. Exposure of semen to urine resulted in a significant dose-dependent decrease in the percentage of motile spermatozoa (MOT) and both velocity variables (VSL and VCL). Amount of urine contamination also affected MOT, VCL, VSL and LIN value during short-term storage. In conclusion, it is important to avoid semen contamination by urine when using the stripping procedure in the Eurasian perch, either for controlled reproduction or sperm preservation.

Collection of Gametes

Within this chapter, general information on the characteristics of Eurasian perch gametes is given. In addition, methods possible to apply for their collection for the purpose of controlled fertilization are briefly described. Practical advice on the recognition of moment of ovulation as well as sperm collection is given.

Harvest, Transport of Spawners, Prophylaxis

Within this chapter the theoretical background, as well as detailed practical advices of collection of the spawners of Eurasian perch from lakes and from earthen ponds are discussed. A special attention is paid to the time of collection and additionally, the methods of transportation as well as basic prophylactic methods are described.

Short- and Long-Term Storage of Gametes

This section characterizes the importance of short and long-term storage of gametes as well as the theoretical background of successful storage of eggs and sperm. Considering eggs, a brief explanation on the effect of storage time on egg quality was described which turned into practical recommendations in this aspect. A detailed protocol of short-term sperm storage as well as a commercially applicable cryopreservation protocol are given.

Hatchery Manipulation and Broodstock Selection

This chapter provides the reader with the theory on the stress and its possible effect on the reproduction outcome and thus justifies the described practical recommendations on the manipulation of the spawners of perch, including the tips for safe and efficient anaesthesia procedures. It additionally focuses on the recognition of the sex of fish allowing effective selection of the broodstock for a controlled reproduction purposes.

Incubation and Hatching

The chapter provides both theoretical background and practical recommendations regarding the incubation procedure. A special emphasis was put on the methods allowing reliable verification of the fertilization success as well as gamete quality. Additionally, incubation devices as well as the optimal conditions for incubation and hatching of larvae were described.

Evaluation of Gamete Quality

Practical guidance considering applicable methods of gamete quality evaluation is preceeded by a theoretical introduction into the definition of gamete quality. In addition, the potential hatchery-related factors of gamete quality are briefly described.