Dwarf Dolly Varden Salvelinus malma (Salmonidae) from Mountain Lakes of the Kamchatka Subnival Belt

Abstract—

Charrs of the genus Salvelinus (Salmonidae) exhibit diverse patterns of heterochrony throughout their ontogeny, resulting in contrasting intraspecific phenotypic variation. This study focuses on isolated populations of Dolly Varden charr, Salvelinus malma, inhabiting cold-water lakes within the subnival belt on the Kamchatka Peninsula. Our study reveals a previously undescribed trend towards paedomorphosis in these populations. Specialization is associated with inhibition of somatic growth compared to the widely distributed migratory (anadromous and river-lake) Dolly Varden from open water systems. Juvenile charrs from landlocked lakes differ in relatively high muscle fat content. Rates of sexual maturation and morphological differentiation remain similar to those of migratory populations. Paedomorphic trends in skull structure are insignificant and the numbers of meristic serial elements do not decrease. Charrs from landlocked mountain lakes grow to a maximum length of 20 cm reaching an age of eight to nine years, while the median age of spawners is 6.2 years. Migratory charrs have the same lifespan, but spawners are 1.6–2.0 times larger. Dwarfism tends to evolve over a small number of generations, as similar phenotypes have been described in populations from the lakes originated more than 12 000 and 400 years ago.