Environmental Factors Influencing Fish Species Distribution in Irrigation Channels around Ariake Sea, Kyushu, Japan

Abstract

Freshwater ecosystems have suffered a long history of anthropogenic disturbances that are responsible for declining fish populations. Fish populations in irrigation channels, in particular, still remain unprotected and relatively unstudied. This study looked to investigate what environmental variables and anthropogenic disturbances had the greatest influence on fish species distribution in irrigation channels. Fish sampling and environmental data collection was conducted throughout six municipalities, spanning 43 sites, in southern Fukuoka, Kyushu, Japan. A total of 37 fish species and 17 environmental variables were statistically analyzed using detrended correspondence analysis (DCA) and receiver operating characteristic (ROC) curve analysis. DCA results showed that channel width, channel substrate and submerged plants had a statistical correlation with fish species distribution. We believe proper management of irrigation channel substrate conditions and macrophyte cover will go a long way in supporting fish species biodiversity and reducing pressure from invasive species. ROC curve analysis revealed a disparity in the environmental preferences of endangered and invasive species. This result suggests that the distribution of endangered species in irrigation channels may be heavily influenced by invasive species. Further research must be done before drafting an effective management solution