1. Fertilization Method
(1) Select white-tailed pike with a maturity age of 2+ years, weighing between 700 and 1000 grams as broodstock. This ensures high-quality gametes for successful fertilization.
(2) Dry insemination is applied. After the eggs are collected, talcum powder is used to remove any stickiness. During artificial insemination, the fish is first wiped with a clean cloth, and the female eggs are gently squeezed into a dry container. It's crucial to avoid contact between the unfertilized eggs and water to prevent premature swelling, which can reduce the fertilization success rate.
2. Fertilization Process
(1) The first three days after fertilization are critical, as this is when the sperm-egg binding is unstable. Avoid any stirring during this period to ensure proper development.
(2) Maintain the pH level between 7.5 and 8. If the pH is too low, it can be adjusted using analytical-grade sodium bicarbonate to create an optimal environment for egg development.
3. Incubation
(1) The incubation density should be set at 150,000 to 300,000 eggs per square meter in the hatching frame. Proper spacing helps maintain good water flow and oxygen levels.
(2) Incubate in low-light conditions. The first two days are sensitive periods, so light and vibration must be minimized. As the embryos develop, the color of the eggs changes from yellow to yellowish green, eventually turning dark brown. Newly hatched fry have a sticky area on the back of their heads, allowing them to adhere to the brown sheets or cage walls.
(3) Temperature should be increased gradually during incubation, no more than 0.5°C per hour. The ideal water temperature ranges from 8°C to 12°C, and dissolved oxygen levels should remain between 7 and 9 mg/L.
(4) Regularly clean and inspect the screens around the hatching box and the outlet filters to ensure unobstructed water circulation.
(5) In the early stages of incubation, reduce the water flow to make it easier to handle the eggs. Excessive water current may damage or kill the eggs.
4. Hatching
(1) Remove the fry immediately after the egg membranes begin to break open. Be careful not to let the fry sink to the bottom along with the egg membranes, as this can lead to suffocation.
(2) Adjust the stocking density in the fry pool based on the growth of the fish. Overcrowding can cause oxygen depletion and lead to mass mortality.
(3) Use running water for the fry pool, ensuring that dissolved oxygen levels meet the required standards. Aeration can be used to increase oxygen, but over-aeration can harm the fry by causing hypoxia and congestion.
5. Seed Stocking
(1) Choose healthy seedlings with strong vitality, good body condition, and no signs of disease or injury. Ensure they are of uniform size for consistent growth.
(2) Disinfect the seedlings before stocking. Soak them in a 3% to 5% saltwater solution for 3 to 5 minutes to prevent infections like water mold.
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