The Australian silver plover (Bidyanus bidyanus) is native to the Murray-Darling River basin in Australia. Body color is silver and white, with less intermuscular thorns, delicious meat, small head, large edible parts, omnivorous food, and no mutual food, and rapid growth. Is a wide-temperature fish, suitable for freshwater ponds, reservoir breeding. In recent years, the fish has been introduced from the Taiwan Province and cultivated in the Minnan region to obtain better results. Since 1999, the author has conducted trials of artificial propagation of silver cocoons and was successful this year.
1 Materials and Methods
1.1 Broodstock
1.1.1 Source of broodstock. The broodstock used in this experiment was derived from the introduction of 3cm silver seedlings from Taiwan in May 1998 and cultivation in local ponds.
1.1.2 broodstock selection. Select weights of 1.1 to 1.2 kg, fish abdomen enlargement, obvious ovarian contours, abdomen softer females, and males weighing 0.8 to 1 kg, light pressure fish abdomen with milky white semen.
1.2 The broodstock picked out by artificial production is divided into two injections of oxytocin. The first needle was injected with LRH-A. The females were weighed at 0.5 μg/kg and the males were not injected. The second shot was injected with HCG. The females were weighed at 1500 IU/kg, and the males were halved. This experiment was conducted in two batches. See Table 1 for details.
1.3 Spawning and hatching
1.3.1 Spawning. The broodstock injected with the oxytocide is placed in the spawning pool of the fish and micro-flowing water, allowing it to naturally fertilize its own eggs.
1.3.2 Fry hatching. After the broodstock lays eggs, the eggs are collected and counted, and then placed in the hatching loop water to hatch. In addition to flowing water, the ring road is also pumped with air pump to increase dissolved oxygen. Spawn rate was calculated 12 hours after spawning. Daily management methods are the same as home fish hatching.
1.4 emergence. After the fish was filmed, the fish activity was observed. When the fish fry developed to be able to swim flat, the egg yolk was fed in the hatchery ring and counted when the fish was transferred to the pond on the seventh day after the film was released.
1.5 Control of spawning and fry hatching water and water temperature. Spawning ponds and incubating waters were all pumped with groundwater and pooled water to keep the water temperature stable between 24°C and 26.5°C.
1.6 Measure the water temperature at regular intervals, observe the spawning of the broodstock, collect the egg count in time and make a record.
2 Results The results of oxytocin production and fry hatching are shown in Table 2.
3 Summary and discussion
3.1 This experiment shows that silver cocoons that have been cultivated in ponds for two years are reachable and mature. According to our observation, male fish can mature one year earlier. Using these sexually mature silver cockles as broodstock, when the water temperature is between 24°C and 26.5°C, the first needle is injected with LRH-A and the second needle is injected with HCG, and the broodstock is able to self-react 28 to 30 hours after the first needle is injected. Spawning and fertilization. In the estrus of the fish, a number of male fish were observed chasing 1 female for spawning and rowing.
3.2 Silver maggot fertilized eggs are smaller, egg diameter is about 2mm, there are oil balls, in the state of no water or pumping, fish eggs sink, there is water or pumping, the eggs float.
3.3 When the fertilized eggs are at a water temperature of 24°C to 25°C, about 30 hours, when the water temperature is between 24.5°C and 26.5°C, the fry is hatched for about 26 hours.
3.4 The freshly hatched silver fish seedlings require higher oxygen in the water than the fry. In the early morning of the first batch of this experiment, due to power outages, the suffocation of fish fry occurred in the hatchery passage of the silverfish fry and the death of the fry occurred. However, the density ratios of the herring and white mullet fry with different water sources in the same water source and hatched in the same period were used. The silver cockroach was several times higher, but only the fry were floating and no dead seedlings occurred.
3.5 On the 4th day after the hatching of the silver larvae, the egg yolks were directly fed in the hatching ring, showing that there was food in the intestine of the fry. On the 5th day, there were still oil globules below the intestine. When looking at the fish plate, the fry swims quickly. When the swimmer fish sinks to the bottom, the fish poses sideways.
3.6 When the abdomen is lightly pressed during the breeding season, sexually mature males have milky white semen. However, it is worth noting that a silver bream with a body weight of 500 grams or more accumulates a large amount of fat in the body, and the abdomen expands. Therefore, when selecting females, we must choose a large abdomen with a clear and fluent outline of the ovaries to prevent misunderstanding. .
3.7 On May 30th we dissected 2 and female fish of the same age and weighing 1.5 kg. We found that the ovary of 1 fish was much smaller than the ovary of the other fish, and there may be a tendency to degenerate. The fertilization rate of eggs is only about 50%, which may be related to the maturity of the gonadal development of fish. Therefore, the time for intensive human production can be carried out more than half a month earlier. It is to be further explored whether the bred broodstock can mature again within one year.
3.8 The use of LRH-A and HCG in two injections of silver oysters can achieve the effect of oxytocin production. However, whether or not two injections of oxytociculants are needed, the effective dosage of different oxytocins remains to be further explored.
1 Materials and Methods
1.1 Broodstock
1.1.1 Source of broodstock. The broodstock used in this experiment was derived from the introduction of 3cm silver seedlings from Taiwan in May 1998 and cultivation in local ponds.
1.1.2 broodstock selection. Select weights of 1.1 to 1.2 kg, fish abdomen enlargement, obvious ovarian contours, abdomen softer females, and males weighing 0.8 to 1 kg, light pressure fish abdomen with milky white semen.
1.2 The broodstock picked out by artificial production is divided into two injections of oxytocin. The first needle was injected with LRH-A. The females were weighed at 0.5 μg/kg and the males were not injected. The second shot was injected with HCG. The females were weighed at 1500 IU/kg, and the males were halved. This experiment was conducted in two batches. See Table 1 for details.
1.3 Spawning and hatching
1.3.1 Spawning. The broodstock injected with the oxytocide is placed in the spawning pool of the fish and micro-flowing water, allowing it to naturally fertilize its own eggs.
1.3.2 Fry hatching. After the broodstock lays eggs, the eggs are collected and counted, and then placed in the hatching loop water to hatch. In addition to flowing water, the ring road is also pumped with air pump to increase dissolved oxygen. Spawn rate was calculated 12 hours after spawning. Daily management methods are the same as home fish hatching.
1.4 emergence. After the fish was filmed, the fish activity was observed. When the fish fry developed to be able to swim flat, the egg yolk was fed in the hatchery ring and counted when the fish was transferred to the pond on the seventh day after the film was released.
1.5 Control of spawning and fry hatching water and water temperature. Spawning ponds and incubating waters were all pumped with groundwater and pooled water to keep the water temperature stable between 24°C and 26.5°C.
1.6 Measure the water temperature at regular intervals, observe the spawning of the broodstock, collect the egg count in time and make a record.
2 Results The results of oxytocin production and fry hatching are shown in Table 2.
3 Summary and discussion
3.1 This experiment shows that silver cocoons that have been cultivated in ponds for two years are reachable and mature. According to our observation, male fish can mature one year earlier. Using these sexually mature silver cockles as broodstock, when the water temperature is between 24°C and 26.5°C, the first needle is injected with LRH-A and the second needle is injected with HCG, and the broodstock is able to self-react 28 to 30 hours after the first needle is injected. Spawning and fertilization. In the estrus of the fish, a number of male fish were observed chasing 1 female for spawning and rowing.
3.2 Silver maggot fertilized eggs are smaller, egg diameter is about 2mm, there are oil balls, in the state of no water or pumping, fish eggs sink, there is water or pumping, the eggs float.
3.3 When the fertilized eggs are at a water temperature of 24°C to 25°C, about 30 hours, when the water temperature is between 24.5°C and 26.5°C, the fry is hatched for about 26 hours.
3.4 The freshly hatched silver fish seedlings require higher oxygen in the water than the fry. In the early morning of the first batch of this experiment, due to power outages, the suffocation of fish fry occurred in the hatchery passage of the silverfish fry and the death of the fry occurred. However, the density ratios of the herring and white mullet fry with different water sources in the same water source and hatched in the same period were used. The silver cockroach was several times higher, but only the fry were floating and no dead seedlings occurred.
3.5 On the 4th day after the hatching of the silver larvae, the egg yolks were directly fed in the hatching ring, showing that there was food in the intestine of the fry. On the 5th day, there were still oil globules below the intestine. When looking at the fish plate, the fry swims quickly. When the swimmer fish sinks to the bottom, the fish poses sideways.
3.6 When the abdomen is lightly pressed during the breeding season, sexually mature males have milky white semen. However, it is worth noting that a silver bream with a body weight of 500 grams or more accumulates a large amount of fat in the body, and the abdomen expands. Therefore, when selecting females, we must choose a large abdomen with a clear and fluent outline of the ovaries to prevent misunderstanding. .
3.7 On May 30th we dissected 2 and female fish of the same age and weighing 1.5 kg. We found that the ovary of 1 fish was much smaller than the ovary of the other fish, and there may be a tendency to degenerate. The fertilization rate of eggs is only about 50%, which may be related to the maturity of the gonadal development of fish. Therefore, the time for intensive human production can be carried out more than half a month earlier. It is to be further explored whether the bred broodstock can mature again within one year.
3.8 The use of LRH-A and HCG in two injections of silver oysters can achieve the effect of oxytocin production. However, whether or not two injections of oxytociculants are needed, the effective dosage of different oxytocins remains to be further explored.
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