20 MARCH 2016 • WORLD AQUACULTURE • WWW.WAS.ORG scale stocking of whitefish larvae in specifically selected small floodplain reservoirs immediately after ice breakup. The basic requirements for such reservoirs are a small number of predatory fish due to winter freezing and the availability of a hydrological connection with the river during summer floods. Mass appearance of juvenile whitefish in the river channel starts when the river water level begins to recede after the flood peak and water in floodplain lakes warms to 16-18 C. By this time, juveniles reach about 1-5 g. The average survival rate of stocked larvae is 40 percent. The total number of juvenile grown this way reached 106 million in 2009. There were 92 million juveniles released in the Ob River basin in 2015, including 74 million C. peled and 13 million C. muksun (Fig. 3). Extensive Aquaculture of Whitefish in Lakes The role of commercial whitefish farming is growing in the context of declining stocks of commercial fish from natural populations. The main form of whitefish aquaculture in the Urals and Western Siberia is extensive farming in lakes. The main species of lake fisheries are C. peled and its hybrids. Currently, about 3,000 t of whitefish are caught from small- and medium-size lakes in the forest-steppe and steppe zones of the Urals and Siberia. Most lakes stocked with whitefish have no other fish at all or have only crucian carp, which does not prey on whitefish larvae. This is the main factor that determines survival rate of early larval whitefish in these lakes, even without rearing. Single-season growing of whitefish usually requires lakes of 1 to 50 km2 with an average depth of 2-3 m, a water salinity 1-8 g/L and pH of 7.5-9.0. These lakes are usually eutrophic and the average The Ob River is one of the largest rivers in the world. The basin area, about 3 million km2, is the largest in Eurasia. The main part of the basin is located in the West Siberian Lowland in territory of the Russian Federation (Fig. 1). The part of the basin with the Russian Federation only that may be used for fishing industry is colossal (156 km2). Stocks of whitefish (Coregonus sardinella, C. autumnalis, C. peled, C. tugun, C. lavaretus pidschian, C. muksun, C. nasus, Stenodus leucichthys nelma) are the main fishery resources of the Ob River basin, considering its climatic features. An average of 11,000 t of whitefish was caught in the 1970s to 1980s, but natural stocks of whitefish have declined significantly in recent years. Annual catches have fallen from 6,120 t in 2004 to 4,730 t in 2014. The total catch of whitefish in the region dropped to a record low value of 3,001 t in 2015 (Fig. 2). The most catastrophic situation is with C. muksun. Catches of this species decreased from 552 t to 51 t during the same period. This has resulted in a temporary ban on commercial fishing of C. muksun and S. l. nelma since 2015. The main reasons for the decline in whitefish resources are pollution of the feeding and wintering zones of whitefish by the oil industry and longer periods of low water level that occurred in the basin from 2008 to 2013. Artificial Propagation and Stocking of Floodplain Lakes To compensate for negative impacts on whitefish populations, there has been an increase in artificial propagation activities. According to biologically-based calculations, the annual needs for basin recruitment of whitefish fry range from 0.3 to 1.6 billion. The current approach of stocking the Ob River basin is massModern Aquaculture of Whitefish in the Ob River Basin of Siberia, Russia Alexander Litvinenko, Sergei Semenchenko, Natalia Smeshlivaya,* and Patrick Sorgeloos FIGURE 1. Map of whitefish farms in the Ob basin.1 – Kharp hatchery, 2 – the egg collection base Rahtynya, 3 – Ugra hatchery, 4 – Tobolsk regional fish farm, 5 – Lake Volkovo, 6 – Kyshtymskoe fish farms, 7 – Chebarkul hatchery. FIGURE 2. The species composition of the total catch of whitefish in the Ob basin in 2015.
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