ИСТИНА

In summer 2011 charr larvae were for the first time sampled close to natural spawning grounds in the tributaries of Lake Kronotskoe (rivers Uson, Unana, Krasheninnikova, Tundrovyi creek) and in the lake proper, near the outlet of the Kronotskaya River. They could not be unambiguously identified with the charr forms and species inhabiting the lake. Patterns of skeletal development were studied in cleared and stained individuals 20 – 55 mm FL. Each sample is characterized by different degree of the development, in the relation to body length, of several skull bones (toothed bones and/or bones bearing seismosensory channels, supraethmoideum, operculum, gill arches, and branchiostegal rays), of the axial skeleton (neural and haemal arches, vertebrae centrae, praedorsalia) and the skeleton of fins. These differences can be caused by different hydrological regimes, temperature dynamics and differencses in the food resources at riverine and lacustrine spawning grounds. Charr in the sample taken in the lake differed from all charr in the riverine samples in meristic characters, namely in the total number of rays in the dorsal and anal fins (15-18, 16.8 versus 14-16, 15.0 and 13-15, 14.3, and 12-14, 13.5). In larvae from riverine environments, anomalies in the development of fin rays, branchiostegal rays, axial skeleton elements were detected. It is supposed that the available spawning areas of charr much exceed the potential of food resources of the Kronotskoe Lake lacustrine system, this implying high level of competition and high rate of morphological specialization already during the larval and juvenile periods. The results are compared with the data on the development of the anadromous Dolly Varden from Kamchatka.