Wetlands constructed to treat stormwater are often inhabited by animals that can suffer impairments. Such effects will be exacerbated if animals are caught in ‘ecological traps’ whereby they mistakenly prefer sites where their fitness is reduced. Traps can compromise population persistence, so assessing if the fitness of animals is lower at stormwater than natural wetlands, and if animals can avoid poor quality locations can guide management efforts.

          We tested if the fitness (e.g. survival, development) of the threatened dwarf galaxias (Galaxiella pusilla) was lower at stormwater wetlands around Melbourne, and if so, whether fish avoid poor quality sites. We also examined the potential effects of the invasive mosquitofish (Gambusia holbrooki) across the life cycle of dwarf galaxias, and whether G. pusilla recognise this threat.

            We found that G. pusilla are susceptible to ecological traps. Survival was lower at stormwater wetlands and fish suffered delayed ovarian maturation, and mosquitofish ate larvae and disrupted breeding. However, G. pusilla did not avoid water from stormwater wetlands or cues from G. holbrooki. We discuss our results in the context of how insights from animal behaviour can inform threatened species conservation in fragmented urban landscapes.