California bass are generally sexually mature for more than one year and generally enter the spawning period when the water temperature reaches 18-26°C. In Jiangsu area, breeding can begin in early to mid-April every year when the water temperature reaches above 15°C. Let’s take a look at how California bass undergoes artificial labor induction.
(1) Preparation of spawning pools Before the breeding season, the spawning pools should be prepared according to the production scale. The location of the spawning pool should be chosen in a place with convenient filling and drainage and a quiet environment.
①Concrete pond
A cement pond of 10-30 square meters or larger can be used as both a spawning pond and a hatching pond. The water depth is 0.4-0.5 meters. Nests for spawning fish should be laid out around the bottom of the pond, one every 1-2 meters. The density of broodstock stocking to induce labor is 2-3 groups/m2.
② Earthen pond
An earthen pond with a sandy bottom and a slope is ideal for spawning ponds. The area is 600-1500 square meters, the water depth is 0.5-1 meter, and the pool slope ratio is 1:2 or 1:3. This makes it easy for the broodstock to dig and build fish nests and is not easily washed away by wind and waves. Some stones and bricks should be piled around the pond, and some aquatic plants should be planted to prepare the parent fish to build nests before they lay eggs. When the area is less than 5 acres and the water depth is about 1 meter, the density of spawning broodstock is 20-40 pairs/acre.
③Fish nest setting
California bass has the habit of building nests before spawning. Female fish lay eggs in fish nests, so fish nests should be set up in the spawning pond. On the one hand, it adapts to its ecological habits, and on the other hand, it can promote the estrus and spawning of broodstock.
(2) Induction of labor
Artificial induction of labor can be done with one injection or two injections. Oxytocinators can be used alone or in combination. When using 2 injections, the interval is generally 6-8 hours. The dosage of inducing labor can be used as follows:
Carp pituitary gland: The dosage is 5-6 mg per kilogram of female broodstock, divided into 2 injections. Inject 15% of the full dose in the first injection, and inject the remaining amount 12-14 hours apart. The male broodstock is given 2 mg per tail, and the female fish is injected once when the second injection is given.
hcg ten pg: Use commercially available chorionic gonadotropin mixed with carp pituitary gland. The dose of one injection is hcg800 international units and 3 mg of pituitary gland per kilogram of female broodstock, and the dose of male broodstock is halved.
hcg: Chorionic gonadotropin 2000-4000 international units per kilogram of female broodstock.
After the California bass is induced to give birth, the effect takes a long time, and the length of time required for different broodstock varies. When the water temperature is 15℃, the effect time is about 100 hours; when the water temperature is 16-18℃, the effect time is 48-52 hours; when the water temperature is 22-26℃, the effect time is 18-30 hours. Sometimes, male and female parent fish are seen in estrus in the nest for 1-2 consecutive days, and eggs are not seen until the third day; sometimes the effect lasts as long as 11 days. Only by mastering these characteristics of California bass can you not miss the opportunity to collect fertilized eggs.
(3) Spawning and fertilization
When the optimum temperature for reproduction is reached, the male fish first selects a nest or builds a nest. When a female fish approaches, the male fish will push his head against the female fish's belly to attract the female fish into the nest. When reaching the climax of estrus, the male and female fish press their abdomens close to each other and swim parallel to the top of the nest. Often the female fish is on top and the male fish is on the bottom, with their tails intertwined and their abdomen facing the fish nest. The female fish's body is shaking constantly, the eggs slowly flow out of the reproductive pore, and the male fish ejaculates at the same time. The female then swims out of the nest and the male follows. Generally, after 3-5 minutes, both male and female parent fish return to the nest and are repeatedly stimulated to lay eggs and fertilize again by butting their abdomens. Repeat this many times. The fertilized eggs will attach themselves to the fish nest objects. When the female fish has finished laying eggs, the male fish will drive the female fish out of the nest and the male fish will protect the eggs. The spawning environment should be kept quiet, with regular micro-flow or maintenance of micro-flow. However, eggs are generally laid more intensively at night on the 2nd to 4th day. On the 5th to 6th day after entering the pond, the broodstock will swallow the eggs due to lack of food. After the broodstock group has basically finished spawning, use a thin net to catch all the broodstock.