Influence of trout on dwarf galaxiid habitat preferences - dataset

Introduced salmonids are a major threat to native non-migratory galaxiid fishes in New Zealand, yet evidence for predator-driven shifts in habitat use remains mixed. This study experimentally tested whether dwarf galaxiids (Galaxias divergens) altered their habitat preferences in response to the presence or odour of rainbow trout (Oncorhynchus mykiss). Two habitat contrasts were examined: coarse versus fine substrate, and open versus vegetated cover. Fish were observed under three predator treatments: trout present, trout odour only, and trout absent. Galaxiids showed a weak increase in use of fine substrate under the odour-only treatment, but no differences between trout-present and trout-absent treatments, and no consistent response to vegetation cover. Overall, predator cues had little influence on galaxiid habitat use. These results suggest that predator recognition and avoidance behaviour in G. divergens is subtle, context-dependent, or limited by sensory constraints. The consistent preference for coarse substrate reinforces its ecological importance, even in the absence of strong anti-predator shifts. Management actions aimed at maintaining or restoring coarse benthic habitat and reducing fine sediment inputs may improve habitat quality and resilience of galaxiid populations, irrespective of trout presence.The dataset enclosed contains the dwarf galaxiid count in either vegetation-free or over fine sediment for each flume, treatment and time step from the experiment.