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 (<i>Galaxias divergens</i>) altered their habitat preferences in response to the presence or odour of rainbow trout (<i>Oncorhynchus mykiss</i>). 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 <i>G. divergens</i> 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.<br><br>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.