Effect of water gates in rivers on intra stream dispersal of freshwater fish population: evaluation using a surrogate indicator species

• Published in: Environmental biology of fishes 2023-10, Vol.106 (10), p.1923-1931
• Main Authors: Iitsuka, Yumi, Ohta, Tamihisa, Sazawa, Kazuto, Nishio, Masaki, Kawakami, Ryosuke, Yamazaki, Yuji
• Format: Article
• Language: English
• Subjects: Animal population; Animal Systematics/Taxonomy/Biogeography; Biomedical and Life Sciences; Creeks & streams; Ecosystems; Environment; Fish; Fish populations; Freshwater; Freshwater & Marine Ecology; Freshwater fish; Freshwater fishes; Hybridization; Indicator organisms; Indicator species; Inland water environment; Life Sciences; Mitochondrial DNA; Mollusks; Nature Conservation; River ecology; Rivers; Water shortages; Zoology
• ISSN: 0378-1909; 1573-5133
• DOI: 10.1007/s10641-023-01470-6

Large-scale farming involving artificial water management, including the installation of water gates on rivers, has greatly affected freshwater biodiversity. The aim of the present study was to evaluate the effects of water gates and/or interspecific hybridization on genetic population structure of the surrogate indicator species Rhodeus ocellatus subspecies (i.e., R. o. kurumeus and R. o. ocellatus ) on threatened indigenous bitterlings in the rivers of the Himi region, Toyama Prefecture, central Japan. Microsatellite DNA analysis, comprising polymorphic 11 loci, of samples collected from multiple river sites in a paddy field ecosystem showed that the number of loci deviating from Hardy–Weinberg equilibrium (HWE) tended to decrease with the hierarchy of population units in the order of river systems, tributaries, and sites. Repeated hybridization of R . ocellatus subspecies over generations in the study area suggests the unlikeliness of a genetic composition originating from the past effecting current genetic structure. Consequently, we hypothesize that water gates have restricted intra stream dispersal, affecting the genetic heterogeneity within the R . ocellatus subspecies population, leading to deviations from the HWE. Our study describes the invasive R . ocellatus subspecies as a useful surrogate indicator for indigenous threatened species with a small population size. Our study also suggests a stronger influence of water gates than hybridization on R . ocellatus subspecies.