From distraction to habituation: Ecological and behavioural responses of invasive fish to anthropogenic noise

Abstract

Abstract Tolerance to human‐induced environmental stressors is known to contribute to the spread and success of invasive species but their response to anthropogenic noise has still to be explored. Anthropogenic noise might modulate the trophic impact of invasive species and their competitiveness against native species. We used an ecological approach through the derivation of the functional response to test whether the strength of the trophic interaction between the invasive pumpkinseed sunfish and Chaoborus larvae was influenced by motorboat noise, with or without pre‐exposure. Boat noise decreased maximum feeding rate in the fish that never experienced boat noise before, resulting in a lower functional response compared to the ambient noise condition. We hypothesised that fish were distracted and reallocated a part of their finite attention to this new acoustic stimulus at the expense of prey processing. The distraction effect weakened with repeated exposure suggesting a habituation process. Although we cannot exclude persistent adjustments in behaviour, we did not find evidence for altered predation by fish pre‐exposed to boat noise. Pumpkinseed sunfish did not exhibit clear symptoms of a behavioural stress response. Chaoborus movements were more numerous under boat noise but this was unlikely to influence trophic interaction strength relative to fish behaviour. Local species might experience increased trophic competition if they are disturbed and do not habituate contrary to invasive species.