Abstract
White-spotted charr (Salvelinus leucomaenis leucomaenis) is an anadromous fish that has been severely harmed by human land-use development, particularly through habitat fragmentation. However, the anthropogenic impacts on populations of this species have not been evaluated, except those on small dammed-off populations. Using multiplexed ISSR genotyping by sequencing, we investigated the genetic structure of white-spotted charr in four tributaries in the upper section of the Kanayama Dam in the Sorachi River, Hokkaido Island, Japan. There were no distinct genetic structures (FST = 0.014), probably because some active individuals migrate frequently among tributaries. By model-flexible demographic simulation, historical changes in the effective population size were inferred. The result indicates that the population size has decreased since the end of the last glacial period, with three major population decline events, including recent declines that were probably associated with recent human activities. Nevertheless, populations in the watershed upstream of the Kanayama Dam are still expected to be at low risk of immediate extinction, owing to the large watershed size and the limited number of small check dams. An effective conservation measure for sustaining the white-spotted charr population is to maintain high connectivity between tributaries, such as by providing fishways in check dams during construction.
Highlights
Anthropogenic impacts on freshwater ecosystems are numerous and include flow alteration, pollution, species invasion, water abstraction, fisheries activities, and climate change [1,2]
There were no records of white-spotted charr being artificially released in this area, so we considered all caught individuals to be native
This study revealed the population structure and demographic history in the upper section of a large dam
Summary
Anthropogenic impacts on freshwater ecosystems are numerous and include flow alteration, pollution, species invasion, water abstraction, fisheries activities, and climate change [1,2]. Since the latter half of the 20th century, human land-use activities and resource exploitation have had substantial effects on stream-dwelling organisms [3]. In the case of migratory fishes, such as salmonids, the effects of impassable barriers are severe because they cannot complete their life cycles within isolated stream fragments [7]. White-spotted charr (Salvelinus leucomaenis) is a cold-water adapted salmonid fish that is commonly distributed in mountain streams of Far East Asia [8].
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