Ichthyofauna in a highly urbanised area (Kitakyushu metropolitan area, Fukuoka, Japan)

A fish survey was conducted at 100 locations within the Kitakyushu metropolitan area during the summer period (from 16 July to 4 October 2024), focusing on river sections modified by channel straightening and concrete lining due to urbanisation. The survey resulted in collecting 30 genera and 32 species from nine orders and 19 families, for a total of 9,253 individuals. Amongst the species collected, rare species, such as the Bitterling, <i>Liobagrus reini</i> and <i>Misgurnus anguillicaudatus</i>, were also found (The Japanese Red List). Although the number of individuals was limited, these native rare species were found in inhabited rivers significantly altered by human activity. Additionally, invasive species including <i>Lepomis macrochirus</i>, <i>Micropterus salmoides</i> (Lacepède, 1802) and <i>Channa argus</i> (Cantor, 1842) were recorded. Despite accounting for only 0.5% of the total fish population, the highly predatory nature of these invasive species warrants proactive management, including the enhancement of impounded water environments through structures such as weirs, to mitigate their potential ecological impact.