WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2016 23 whitefish breeding in Western Siberia is the significant distance from the site of eggs collection to the hatchery, up to 1000 km. Equipment is delivered to the hatchery by river due to the poor land transport infrastructure in the North region. Helicopters are used for the transport of collected eggs and fish farmers after freeze-up. Broodfish are captured during the natural spawning migration of natural populations and delivered to a facility on the river for egg collection. Captured female and male broodfish are stocked into cages for conditioning for one week to two months, depending on the timing of capture. Hormonal stimulation of whitefish broodfish is not required. Mass maturation of gametes occurs once spawning temperatures (about 4 C) stabilize. Eggs of whitefish are collected in two ways: a traditional method of manual collection of reproductive products (Fig. 6) and ecological methods (Fig. 7). Sixty to seventy percent of the eggs supplied to Tobolsk are collected using the ecological method. The ecological method of collecting whitefish eggs is based on the natural spawning behavior of broodfish in specially designed cages that enable continuous and automatic collection of fertilized eggs. This technology significantly increases productivity and broodfish remain alive. The main base of egg collection (Rahtynya) is located on the Lyapin River (North Sosva river basin) in the foothills of the Polar Urals (Fig. 1). In October 2015, 613 million whitefish eggs were collected there, including 442 million C. peled eggs that were collected using the ecological method. Broodfish are returned to the river after spawning. Developing Captive Broodstock A major problem with the current technological structure of whitefish spawning in Western Siberia is the shortage of broodfish for collecting eggs. The paucity of natural spawning stocks of the most valuable whitefish species (C. muksun, C. nasus, S. l. nelma) does not allow collection of eggs in sufficient quantity to enable artificial mass reproduction. This problem may be solved through creation of whitefish broodstock in industrial conditions. Such broodstock are maintained in Lake Volkovo, near Tobolsk (Fig. 1). This lake has an area of only 90 ha and is a former riverbed of the Irtysh River. Broodfish cages, 6 m deep, are placed in the lake where the depth is 11-19 m. This depth provides satisfactory temperature conditions during the summer warming of lakes. In winter, most of the surface of the water in cages is free from ice, although air temperatures may sometimes drop to -30 C. This is achieved by the local mixing of water masses by turboaerators, while continuing the feeding of fish. On this farm, 236 million whitefish eggs were collected in 2015, of which 214 million eggs were collected using the ecological method. It is particularly noteworthy that this amount included 82 million eggs of most valuable whitefish species. For the first time, the farm collected 17 million S. l. nelma eggs. This species is the only predator and is fastest-growing whitefish. The relatively low quality of eggs is a temporary drawback in the collection of eggs from cage farms. Egg fertilization ranges from 50 to 70 percent while fertility in eggs from wild broodfish is about 90 percent. Experimental work is in progress to improve the quality of eggs collected in industrial conditions. In particular, adding frozen amphipods (Gammarus) to the diet of whitefish broodfish at the end of the growing season improves fertilization rate by 20 percent in comparison with broodfish that receive only artificial food. Whitefish eggs under natural temperature conditions require incubation for 6 to 7 months before hatching. Incubation time can be reduced 2-3 times by adjustment of water temperature. The period preceding the natural growing season may be used to grow large and viable fingerlings following intensive culture technologies. Gosrybtsentr has developed a recirculation system for incubation and fry growth to implement this approach. Whitefish farming in Siberia is not yet well-developed. The current amount of C. muksun grown in recirculating systems at Omsk is only 3 t/yr. This type of industrial aquaculture will certainly develop further, stimulated by the high price of delicious whitefish products and the ongoing decrease in natural stocks. Notes Alexander Litvinenko, Sergei Semenchenko, and Natalia Smeshlivaya,* State Research and Production Center of Fisheries, Tyumen, Russia * corresponding author: nsmeshlivaya@mail.ru Patrick Sorgeloos, University of Ghent, Belgium FIGURE 7. A line of cages for collection of C. peled eggs by the ecological method on the egg collection base Rahtynya.
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