ИСТИНА

An important factor of Arctic charr diversification is the divergence of reproductive strategies promoting reproductive isolation. Transbaikalia is an area of intensive charr speciation; however, due to the remoteness of mountain populations data on charr reproduction in this region are scarce. We investigated spawning patterns of Arctic charr in 9 lakes differing in size, depth, elevation, temperature regimes and food resources. High variety of these patterns with respect to spawning time, duration, location and depth of spawning grounds and bottom substrate was revealed. Spawning in different popula - tions and sympatric forms takes place in early autumn, late autumn, spring, summer or during more than one season, in the littoral or profundal zone, over rocks or silt and proceeds from two weeks to at least seven months, while difference in spawning time between intralacustrine forms can reach five months. An important driver of the divergence in breeding habits is the competition for spawning grounds, which generally forces smaller less competitive forms to spawn in atypical time and/or place facing the risk of high egg mortality. The limits for such deviations from optimal conditions are imposed by physical parameters of the lakes, e.g. in coldwater high-elevation lakes summer spawning is possible in the littoral zone, while in lower lakes, only in the isothermic profundal zone. We present more detailed information on autumn and spring spawning in parapatric populations of interconnected lakes Kiryalta-3 and Kiryalta-4 and analyze first results of rearing experiments with progeny from artificial crosses within and between different charr populations/ forms.