(1) Feeding and Rearing: The feed for raising fry is generally similar to that of other marine fish species, including rotifers, Artemia nauplii and adults, and small fish. Copepods and clams are also excellent food sources, provided they are of high quality and properly sourced. Fry typically begin feeding around 7 days after hatching. However, since they still have a large yolk sac at this stage, it's important to start feeding them before the yolk is fully absorbed. Unlike some other fish, the false eye (a type of fish) does not go through the "hanging" phase before swimming horizontally. From the moment of hatching, it swims in a horizontal position, so swimming behavior alone cannot be used as an indicator of when to start feeding. The density of rotifers should be more than 2 per milliliter. Figure 5 shows a feeding schedule for reference: from day 7 to day 21 post-hatching, feed with rotifers. Starting on day 11, introduce Artemia nauplii. By day 27, you can add a small amount of minced fish. At this stage, fry cannot swallow large pieces, but they can eat small fragments or even the entire skeleton of a fish. If available, larger prey such as adult Artemia or shrimp can be introduced during feeding. Feed four times a day, with two sessions in the afternoon. Since the nursery is conducted in spring and summer, feeding should occur during daylight hours. The first feeding should be done as soon as possible to prevent fry from fighting due to hunger. The last feeding should be done just before it gets dark.
(2) Stocking Density: The density in the nursery is closely related to the culture techniques used. With sufficient water exchange and enough bait, the stocking density can be increased. The numbers mentioned here reflect the current general practice. False eye fish tend to be more aggressive and cannibalistic compared to other species. The initial density for newly hatched larvae can be up to 5,000–10,000 per cubic meter. As they grow, the density should be adjusted accordingly: 10–15 mm length – 1,500–2,000 per cubic meter; 20–25 mm – 1,000 per cubic meter; 30–35 mm – 600–800 per cubic meter; 40–50 mm – 400–500 per cubic meter.
(3) Preventing Cannibalism: False eye fish, among others, are known to be highly cannibalistic. Fry begin biting each other once they reach about 4 mm in length, usually targeting the caudal and pectoral fins. While some fry can escape, many end up with damaged or incomplete fins. As the fish grow, the problem becomes worse. By the time they reach about 40 mm, they may even bite off the tails of others, leading to death. Currently, there is no method that completely prevents cannibalism, but it can be reduced. Here are some effective strategies:
1. Separate fry of different sizes into different ponds. This helps smaller fry grow better and reduces mortality risk.
2. Provide adequate food. Hunger increases aggression, and overfeeding can reduce biting, although it won't eliminate it entirely. Some believe that certain fish enjoy biting, as seen in cases where cages were chewed or tubes were bitten.
3. Reduce stocking density to lower the chances of aggressive interactions.
4. Consider cutting the teeth of larger fry. This method works best for fry that are about four months old. The teeth are attached to the jaw and must be cut, not pulled. After cutting, the teeth will regrow. Specialized tools like rongeurs are used for this process, and it can help slow down the rate of cannibalism.
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