On the Dolly Varden’s Salvelinus malma (Salmonidae) biology in Kamchatkan spawning rivers of the volcanic areas

Аннотация

Anadromous and stream resident Dolly Varden S. malma were compared in the contaminated and reference rivers across Kamchatka region. Anadromous Dolly Varden’s fry from the polluted and clean rivers were correspondently different by reduced growth rate and narrow length variability. It was observed that juveniles prefer to migrate from the polluted river sections; only seldom fry reaches the smoltification stage at the contaminated sites. The volcanogenic environmental pollution causes paedomorphosis and accelerated sexual maturation in the landlocked brook-dwelling populations. Either the growth rate or the length variability within the age groups were not reduced during the maturation period in the landlocked groups comparing with fish from reference streams. However the weakened individuals with an extremely low body weight were observed among the landlocked fish during maturing. Gonadosomatic index and relative fecundity were comparable for fish from polluted and clean rivers, though relatively high fecundity for the first group was attained by the oocytes size decreasing. Skin cover was damaged; Clark’s condition index and muscle fatness were reduced while liver size was enlarged in either landlocked or anadromous fishes from the polluted water-courses.