WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 55 (CONTINUED ON PAGE 56) by feeding behavior, characterized by targeting and throwing itself on the prey, and appearance, with a dark lump in the stomach that increases in size (Fig. 2). As larval perch grow, they become more mobile, aided by the development of rays in the caudal fin and changes in body muscles, where myotomes take the form of raised side of the letter M. Seeing prey, the larvae swim to it, doing a throw and swallow maneuver. At the seventh stage of development, larvae are able to make quick and sharp turns in all planes. They are held mainly in the upper layers of the water, forming schools that are organized in the daylight hours. At night, the schools dissipate, and larvae are immersed in the lower layers of water, where they remain separately. Improving Cultivation Efficiency Perch larval culture was conducted in the same aquariums where incubation took place in the first stage. Complications were caused by removal of egg ribbon residues. Complete removal of the organic suspension was possible only after the larvae were buoyant. It was necessary to ensure the presence of feed in rearing tanks and to study the feeding behavior of perch in the early stages of development, when larvae grew to 5.7-6.0 mm, and intestinal peristalsis began. In the natural environment, after hatching, the larvae fed in the early days on phytoplankton, rotifers and crustacean larvae. A few days later, their diet included copepods and Daphnia (Eckmann and Imbrock 1996). Natural food organisms contain all the vital substances for growth and development. Protein of live food organisms is composed of 2/3 easily digestible water-soluble and relatively low molecular weight compounds that readily undergo hydrolysis by digestive enzymes (Ponomarevet al. 2002). In aquarium conditions, an experiment of feeding perch larvae with different feeds was carried out (Fig. 3). Before resorption of the yolk sac, feeding of non-feeding larvae with nauplii of Artemia salina and ground chicken egg yolk caused no difference in growth or mortality. By day 14 of culture, there was a complete resorption of the yolk sac and the average weight of non-feeding larvae grown with chicken egg yolk was 18.1 mg and that of perch offered At the moment, cultivation of river perch by intensive methods is in the initial stages of development. Because perch is a predatory species, acquiring viable fry with the developed instinct for live food foraging is a challenge for culturists. Working with early stages of this species is difficult because of the small size of larvae, the need for live food and cannibalism. The main goal of growing larvae and fry at early stages of ontogenesis is to get viable individuals. The Peculiarities of River Perch Post-Embryogenesis In the conditions of the innovation center called Aquabiotechnopark – Scientific Technical Center of Aquaculture, the hatching of perch larvae was observed at 14 С. The average length was 2.5-3.2 mm and weight was 0.3-0.4 mg with a big yolk sac and lipid droplet (Fig. 1). The head of the larvae is pressed tightly to the yolk sac and mouthparts are not developed. The fin fringe extends along the dorsal, caudal and ventral part of the body, stopping at the anal opening, then running to the rear of the yolk sac, with the anus somewhat behind the middle of the body. Pigment is found in the yolk (especially in the rear end) and stellate melanophores are scattered across the surface and lipid droplet. Larvae lie on the bottom, occasionally making vertical movements (Table 1). At a length of 8-9 mm, larvae move mostly in a horizontal plane, staying in the upper layers of water in aquaria and are not clearly visible or sensitive to water flow. Food particles are detected by sight. Feeding and non-feeding larvae are easily distinguished FIGURE 1. River perch larva after hatching. FIGURE 2. River perch larva at a length of 10 mm. FIGURE 3. Growth and survival of perch larvae during feeding with different types of food.
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