Canonical correspondence analysis scatter-plot of species and sites with the environmental variables fitted as vectors. ACR, alien cray fish presence; AFI, alien fish species richness; ALT, altitude; FOR, percentage of forest cover; IHF, fluvial habitat index; LEV, stream level; WCO, water conductivity; WDO, dissolved oxygen in water; WpH, water pH; EOR, Emys orbicularis; MLE, Mauremys leprosa; NAS, Natrix astreptophora; NMA, Natrix maura.