Broad-Scale Environmental Factors Determining Fish Species Composition of River Estuaries in the Japanese Archipelago

Abstract

This study was conducted to clarify the relationship between fish species composition and environmental factors at various scales in river estuaries in the Japanese archipelago. The estuaries harbor diverse fish species composition due to their complex topography, varied climatic zones, and ocean currents. Non-hierarchical cluster analysis classified the fish species composition of 100 river estuaries (58 families, 152 species, and 486,356 individuals) into five groups. The highest number of species was confirmed in the group of river estuaries located in southwestern Japan and flowing into the inner bay (55.1 ± 9.6 species), characterized by an abundance of the number of Gobiidae species. In contrast, the species number was the lowest in the groups consisting of river estuaries that primarily belong to the northern Japanese archipelago (15.3 ± 3.3 species) that were characterized by an abundance of the number of cold-water fishes such as Salmonidae, Pleuronectidae, and Osmeridae. The highest fish species diversity was confirmed in the groups consisting of river estuaries flowing into the inner bays of southwestern Japan, which had a large tidal range (344 ± 132 cm), suggesting that the large tidal differences create a diverse tidal flat environment that supports fish species diversity. These results indicate that regional species diversity and geographical factors influence the classification of fish fauna. In northeastern Japan, the classification was influenced by geographic area and associated water temperature changes, whereas in southwestern Japan, tidal differences and wave effects could be more important. Understanding the factors that influence the fish species composition of a target river is fundamental to estuarine conservation, and the findings of this study provide basic knowledge for conservation.

Evaluation of the Effects of Environmental Factors on Seasonal Variations in Fish Diversity on a Coastal Island in Western Japan

“…For example, the structure of coastal fish communities is potentially influenced by geographical factors (e.g., latitudes and longitudes, coastal topography) [6,7]. Previous studies have discussed ecosystem diversity and fish communities in several domains such as in open oceans, continental shelves, enclosed seas, and estuaries [7][8][9][10][11][12]. Within vast coastal ecosystems, coastal islands are characterized by greater species diversity [12][13][14].…”

Fish fauna and environmental factors in river estuaries of small and medium‐sized rivers on islands significantly influenced by warm currents

“…Occurrence of fish fauna in Tanegashima Island investigated in this study. 1, Minato R. (North); 2, Saikyou R.; 3, Annou R.; 4, Minato R. (North); 5, Asagou R.; 6, Kawawaki R.; 7, Okouda R.; 8, Waseda R.; 9, Injou R.; 10, Mukai R.; 11, Tagiri R.; 12, Adake R.; 13, Oura R.; 14, Abusuki R.; 15, Miyase R.; 16, Koori R.; 17, Shikanaki R.; 18, Ookawa R.; 19, Shimama R.; 20, Tsuka R.; 21, Tanikiri R.; 22, Kuhama R.; 23, Adakaiso R.; 24, Owatase R.; 25, Hamanomachi R.; 26, Kamiishidera R. The distribution area information used to determine climatic zones is based on Kawano et al (2011), Nakabo (2013), and Itsukushima (2023).…”