The turbot is found in the sea from the Mediterranean to the Norwegian coast. In Europe, turbot is a rare breed of fish. In the past 10 years, turbot breeding has continued to develop. The production of turbot increased from 150 tons in 1985 to 3,700 tons in 1998. In the Atlantic coastal waters, turbot naturally reproduces in the summer. However, by artificially controlling the light cycle and water temperature, or only controlling the light cycle, turbot may reproduce throughout the year. The turbot spawned in batches, and spawned up to 10 times during the breeding season. Under conditions of containment, turbot does not lay eggs even if it ovulates naturally, and it requires hand-squeezing eggs. Moreover, due to the irregular ovulation of females during the containment, spawning is not synchronized between females and ovulation is unpredictable. The early and late breeding of female fishes leads to elongated breeding seasons and deviates from the requirements for intensive fish production. From the perspective of ensuring the adequate supply of fish eggs, the production enterprises generally reserve a large number of broodstock. In order to solve this problem, that is, shorten the breeding period and increase the number of ovulation females, French experts conducted a sustained release of granules by implanting gonadotropin-releasing hormone analogues as early as in 1995, inducing spawning of turbot females. Synchronization of spawning females was reported in the recent “Aquaculture†magazine published in the Netherlands in 2000. This article outlines the main results of this study and I would like to refer to domestic turbot breeding and breeding companies. Oxygen Production Method Broodstock Breeding: The female fish used in this study all come from a commercial fish farm on the Atlantic coast of France, namely French Turbot. The study was divided into 2 experiments. The first experiment was conducted from April to June 1995. For early reproduction, the females were cultured under artificial lighting cycles. There were 24 females in total, 12 in the control group, and 12 in the treatment group. The average weight was 4.40.7 kg. . The second experiment was carried out from June to August 1995. The female fishes were cultured under natural light cycle conditions. There were 51 females in total, 20 in the control group, and 31 in the treatment group. The average weight was 5.00.7 kg. In two experiments, the stocking density of females was 8 kg/m 3 . Female breeding water temperature is 141 °C. At the beginning of spawning, the water temperature was adjusted downwards. During the entire spawning period, the water temperature was maintained at 12°C to prevent overcooking of fish eggs. Induction treatment: The sustained release granules used contained 75 μg of gonadotropin-releasing hormone analogues (Luteinizing Hormone Releasing Hormone Analogs) per tablet and were implanted in the back muscle at a dose of approximately 25 μg/kg body weight. Ovulation female ovulation rate comparison: In the first experiment, between the treatment group and the control group, the female ovulation rate, that is, the percentage of ovulation females, no significant difference, but in the second experiment, the treatment group The ovulation rate of females reached 100%, compared with 47% in the control group. Comparison of ovulation synchronization: In the first experiment, in the treatment group, females in the same group, between the first spawning female and the latest spawning female, the ovulation initiation delay was 15 days, while in the control The group is 54 days. In the second experiment, the treatment group had a 28-day delay while the control group lasted more than 70 days. In the first experiment, the entire spawning period of the treatment group continued for 4 weeks. In the second experiment, the final ovulation was not waited until the examination was stopped. However, the entire spawning period of the treatment group did not seem to exceed 6 weeks. The spawning period of the control group was at least 8 to 9 weeks (first experiment) and 13 to 14 weeks (second experiment). In both experiments, the average duration of spawning (16 days) was significantly shorter in the treated individuals than in the control group (26-35 days). In both experiments, there was no significant difference in the number of ovulations per female between the treatment and control groups. However, the ovulation rhythm of the treatment group was faster than that of the control group. The average ovulation interval of the control group was 2.5 to 2.8 days, while that of the treatment group was 1.6 to 1.8 days. Comparison of eggs collected by females: During the entire spawning period, there was no significant difference in total egg production per female between the treatment group and the control group, however, the average egg collection per batch (214 ml) was significant in the treatment group. Higher than the control group (144 ml). During the entire breeding period, in the first experiment and the second experiment, the total eggs collected in the control group were 7 million (12) and 5 million (20) eggs, respectively, and the total egg collection in the treatment group was 2300. Ten thousand grains (12) and 58 million grains (31). Comparison of hatching rate of fish eggs: There was no significant difference in fish egg size between the treatment group and the control group. In production, the fertilization rate in the treatment group (74.7% to 77.2%, average 76.6%) was significantly lower than in the control group (88.2% to 92%, average 89.5%). However, there was no difference in hatching rate. Hormone treatment appears to affect the ovaries, at least during the fertilization phase. The dose of hormones used in this study can be reduced, presumably not impairing ovulation induction, but it can help improve the quality of the egg. From an economic point of view, the use of gonadotrophin-releasing hormone implantation technology is expected to reduce the number of broodstock reserves by 20-30%. In conventional production, during the nursery season, 56% of females ovulate, and the rest either cannot lay eggs or ovulate too late. With the hormone particles, the percentage of ovulating females may increase to 90%.
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