Allometric and ontogenetic larval development of common barbel during rearing under optimal conditions.

The rearing of finfish larvae is a key element in their further culture. Improper breeding protocols may result in high mortality rates, body deformation and growth rate decreases in both the larval and fattening periods. These errors can be avoided by thorough exploration of various aspects of early larvae biology, at least in model fish species. In this study, anatomical and morphological developments were analysed using allometric growth patterns of common barbel, Barbus barbus, larvae reared under optimal controlled conditions. Larvae of common barbel, which is a model species for fish of the genus Barbus, were reared for 30 days at 25 °C in the recirculated aquaculture system (RAS). Four periods of the barbel larval development were identified: pre-flexion (0-5 days post hatching - DPH; total length - TL: 9.5 ±â€¯0.3 to 12.3 ±â€¯0.3 mm), flexion (6-11 DPH; TL 12.4 ±â€¯0.3-15.4 ±â€¯0.3 mm), post-flexion (12-21 DPH; TL 16.1 ±â€¯0.5-21.2 ±â€¯0.8 mm) and juvenile (from 22 DPH; TL from 21.4 ±â€¯1.7 mm). The largest changes in barbel growth were observed during the first two periods of their life (pre-flexion and flexion), which resulted in the frequency of noted flexion points (64.3% flexion points) and was also associated with intensive morphometric growth, primarily the head and tail parts of the body. Despite a low degree of growth progress upon hatching (e.g. no eye pigment, no distinct liver or pancreas, no unobstructed alimentary tract), barbel larvae pass through the larval periods very quickly in comparison to other cyprinids and enter the juvenile period (22 days).

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 application of hCG, CPH and Ovopel in successful artificial reproduction of goldfish (Carassius auratus auratus) under controlled conditions.

Artificial reproduction of fish is one of the main goals of aquaculture production. The aim of this study is to optimize the method of goldfish reproduction under controlled conditions by comparing the effectiveness of carp pituitary homogenate (CPH), Ovopel and human chorionic gonadotropin (hCG), administered as a one-off dose and inducing two spawns in the same fish within a short time period. Goldfish spawners were stimulated with hCG, CPH and Ovopel, and the results were compared to the fish from the control group, comprised of unstimulated fish. In another experiment, spawn were induced twice within an interval of 21 days with the same group of fish. The best results in the first experiment in terms of the percentage of ovulating females and survival to the eyed-egg stage were achieved after administering hCG (100% and 88.7%, respectively). However, the highest fecundity was observed in fish stimulated with Ovopel (89,960 eggs/kg). It was shown in the second experiment that female goldfish produce higher weight of eggs during the first spawning, but the number of eggs/BW ratio was higher during the next reproduction process. Survival, both that of embryos to the eyed-egg stage and that of spawners, is higher during the first reproduction act.

Genetic inactivation of Leuciscus idus L. (ide) oocytes using UV irradiation.

Oocytes of Leuciscus idus were genetically inactivated using ultraviolet (UV) irradiation. Eggs for the experiment were obtained from dark-coloured females, whereas milt was taken from yellow-coloured (recessive marker) males. The survival at the eleutheroembryo stage (free embryo) in all experimental groups fertilized with genetically inactivated spermatozoa was much lower than in control groups. All haploid embryos showed morphological abnormalities, such as a stunted body and a poorly formed retina, and the condition was referred to as the haploid syndrome. The androgenetic origin (haploid or diploid embryos) was checked using a recessive colour marker ('blond'). The optimal doses of UV irradiation were 3,456-4,608 Jm(-2) at which almost 100% haploid embryos were produced at a hatching rate of >15%. Lower UV-ray doses influenced abnormal embryo development. Ploidy level recognition showed a typical value of mean active nucleoli per cell in haploid and diploid (control fish and spontaneous androgenotes) specimens. Abnormal dark embryos were classified as aneuploids.

Preliminary observations on the induction of triploidy in Abramis brama by cold shock.

Cold shock (2 degrees C) lasting for 45 or 60 min was applied to eggs from bream (Abramis brama), beginning at 2, 3, 4, 5, 6, 7 and 8 min after fertilization. The lowest survival rate was observed in those groups treated in which a cold shock started at 4 or 5 min after fertilization. Groups exposed to cold shock lasting for 60 min showed a higher percentage of triploids than in groups shocked for 45 min. The highest yield of triploid embryos was produced by the cold shock which started 8 min after egg fertilization and which lasted for 45 min.