Conectivity solution for huchen Hucho hucho (L.) in human-altered habitats

Abstract

Considering huchen globally endangered (E), and the largest, endemic salmonid fish species, threatened severely by high dams construction, there is a strong need for stopping of its recent decline. Contradiction about the huchen migratory behaviour and consistent records about their lacking from the fish ladders impose considering other solutions compensating the deleterious effects (decline in reservoir sections due to comprehensive alteration of environment; suppression of natural spawning in downstream sections due to hydropeaking; river bed siltation by flushing of reservoirs and decrease in general productivity of the riverine ecosystem; river bed erosion, sinking of the river bed and destroying of gravel bars and send banks, the habitats and spawning grounds) of high dams on them. Establishment of hatcheries revealed only limited success due to making them feral instead of native and due to decrease of genetic variability in fragmented populations. Still remains the strong need for extensive research about the type of fish ladder, slope, flow rate and quality of feeding water and hydraulic signals appropriate for huchen to enter into the ladder in downstream and upstream directions. However, it is also necessary to think about the preconditions that constructors of future high dams and those who runs the recent ones should fulfil to make them more environment-friendly. Those preconditions are related to minimal length of flowing riverine stretches, the least number of tributaries there appropriate for huchen natural spawning, as well as the management measures that are to be applied to minimize the harmful effects of high dams (e.g., accessibility to spawning sites in tributaries, providing of sufficient amount of the water of appropriate quality in them during the spawning season, catch of young-of-the-year huchen and the way of their dispersal throughout the catchment in concern, etc.