Aquatic Animals
Online ISSN : 2434-8643
Fish distribution patterns and habitat characteristics of 23 rivers flowing into Lake Kitaura, eastern Japan
Kensaku OmoriTakahiro MorosawaKouki Kanou
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JOURNAL OPEN ACCESS

2023 Volume 2023 Pages AA2023-1-

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Abstract
The fish distribution patterns and environmental variables in 23 rivers flowing into Lake Kitaura, a shallow inland-sea lake (7 m maximum depth, 36 km2) in Ibaraki Prefecture, eastern Japan, were examined from mid-April to late May (spring) and from mid-September to mid-October (autumn), 2016. A total of 33 fish species, representing 11 families, were recorded during spring and autumn. A cluster analysis based on data for species composition in each river revealed that the 23 rivers fell into one or other of two groups, a large river group with high species richness and a small river group with low species richness. Several different threatened species were found in each group. The relationships between the presence/absence of fish species and environmental variables were analyzed by generalized linear mixed models, the results for 20 species being sufficient for predictability. The number of weirs from a river mouth was negatively related to the occurrence of 10 species, including commercially important lacustrine fishes (e.g., Hypomesus nipponensis and Tridentiger brevispinis), suggesting that upstream movements of these species were negatively influenced by the weirs. In addition, river width, flow velocity, and vegetation-cover ratio were also significant for the presence/absence of many species. In particular, the vegetation-cover ratio positively influenced the occurrence of several threatened species. River restoration programs, including installation of fishways adjacent to the weirs, management of riparian vegetation, and improvement of revetment structures, are necessary to effectively conserve the habitats of the native fishes, which included both commercially important and threatened species in the basin of Lake Kitaura.
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