(1) Feeding and Rearing: The feed used for rearing fry is generally similar to that of other marine fish, including rotifers, Artemia nauplii and adults, as well as finely minced fish. Copepods and clams are also excellent food sources, provided they are of good quality and available. Fry typically begin feeding around 7 days after hatching. Although they still have a large yolk sac, they start eating before it is fully absorbed, so feeding should be initiated in advance. Unlike some other species, the false eye fish do not go through a "hanging" stage; instead, they swim horizontally immediately after hatching. Therefore, swimming behavior alone cannot determine if feeding has begun. The density of rotifers should be more than 2 per milliliter. Figure 5 shows a feeding schedule for reference: feed rotifers from day 7 to day 21 post-hatching. Starting on day 11, Artemia nauplii can be introduced. By day 27, small amounts of minced fish can be added. At this stage, fry cannot swallow large pieces of fish, but they can consume the soft parts of fish, such as bones and internal organs. If conditions allow, larger bait like adult Artemia or shrimp can be offered during fish feeding. Feed four times a day, with two sessions in the afternoon. Since the nursery period is usually during spring and summer, feeding should occur during daylight hours. The first feeding should be done as soon as possible to prevent aggression caused by hunger. The last feeding should be completed before it gets dark.
(2) Seedling Density: The density in the nursery is closely related to culture techniques. With sufficient water exchange and adequate food supply, the density can be increased. The numbers mentioned here reflect current common practices. False eye fish tend to be more aggressive and cannibalistic compared to other species. Newly hatched larvae can be kept at a density of 5,000–10,000 per cubic meter. When they reach 10–15 mm, the density should be reduced to 1,500–2,000 per cubic meter. At 20–25 mm, the density should be about 1,000 per cubic meter, and at 30–35 mm, 600–800 per cubic meter. For fry measuring 40–50 mm, the recommended density is 400–500 per cubic meter.
(3) Preventing Cannibalism: False eye fish and similar species are known for their severe cannibalistic behavior. Fry often start biting each other when they reach about 4 mm in length, primarily targeting the caudal and pectoral fins. While some fry may escape, the damage leads to many fish with incomplete or missing fins once they grow past 5 mm. As they continue to grow, the frequency and severity of cannibalism increase. By the time they reach about 40 mm, they may even bite off tails, leading to death. Currently, there is no method that can completely prevent cannibalism, but its occurrence can be reduced. Under captive breeding conditions, maintaining intact fins remains a challenge. Several strategies can help reduce aggression:
1. Separate fry of different sizes into different tanks or ponds. This helps smaller individuals grow better and reduces the risk of predation.
2. Provide enough food to prevent hunger-driven aggression. Satisfying the fish can lower the number of attacks, although some biting is unavoidable. Some believe that certain fish have an innate tendency to bite.
3. Reduce stocking density to minimize contact and competition among fry.
4. Trim the teeth of larger fry. This method works best for fry over four months old. The teeth are attached to the jaw and must be cut rather than pulled out. After cutting, they will regrow. Specialized tools like rongeurs are used for this procedure, and it also helps slow down the rate of aggression.
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