Foraging intensity of wild mulloway Argyrosomus japonicus decreases with increasing anthropogenic disturbance
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The influence of anthropogenic disturbance on the behaviour of wild animals is increasingly recognised for terrestrial systems. Data on free-ranging aquatic animals are comparatively scarce, and this represents a problem for estimating the consequences of human disturbance for organism fitness and therefore the functioning of aquatic systems. We used acoustic accelerometer and depth transmitters implanted in wild fish and archival stomach content data to test for relationships between the intensity of boating and the activity levels and foraging efficiency of an estuarine predatory fish, the mulloway Argyrosomus japonicus. Increasing boating activity (inferred from week-long trends in underwater noise and local maritime records) was associated with a reduction in activity levels and increased depth distributions of mulloway. Stomach content data from a nearby estuary revealed a far-lower feeding rate and altered diet composition on weekends (when boating activity is greatest) compared to weekdays for this species, and an inferred foraging success rate almost one-third that of weekdays. These data suggest the behaviour and foraging intensity of mulloway is significantly influenced by anthropogenic disturbance. The overall fitness costs of the reduction in foraging success will depend on how readily mulloway can reallocate foraging to less disturbed conditions, and the extent of stress-related responses to disturbance in this species. This study supports earlier predictions that anthropogenic disturbances like noise could have significant impacts on the behaviour and fitness of aquatic animals.
KeywordsAnthropogenic Disturbance Aquatic Animal Acoustic Detection Anthropogenic Noise Underwater Noise
Thanks Jerom Stocks, Grant Clark, Gwenael Cadiou and James McLeod for assistance with fieldwork, and James A. Smith, Stephanie Brodie, Hansjoerg Kunc and two anonymous reviewers for helpful suggestions on the manuscript. We thank B. Pease for supplying stomach content data from the 1977–1979 Botany Bay State Pollution Control Commission Study (database accessed in 2004). Financial support was provided by an Australian Research Council Linkage Grant (LP100100367) with the NSW Recreational Fishing Trust.
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