Noise pollution affects feeding in fish

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Noise pollution irks fish just as much as it does humans, causing them to make mistakes, according to a recent study.

In the study by researchers from the University of Bristol, and published in a recent issue of the online journal PLoS ONE, Julia Purser and Andrew Radford examined the effects of exposing captive Three-spined sticklebacks (Gasterosteus aculeatus) to brief and prolonged noise to investigate how foraging performance is affected by the addition of acoustic noise to an otherwise quiet environment.  

The authors used 24 wild-caught sticklebacks as subjects, maintaining them in aquariums in which ambient noise levels from equipment (e.g. filters) and the external environment were kept to a minimum.

The fish were then subjected to a series of three treatments (prolonged noise, brief noise and silent), with the noise treatment being exposure to white noise with a frequency between 100 and 1000 Hz.  The loudness of the playback noises matched those recorded at the shoreline of lakes where recreational speedboats are active.

The authors placed focal fish into tanks, and then introduced live Daphnia into the tanks.  

Ten seconds after the Daphnia were introduced, noise playback began for the brief-noise and prolonged-noise treatments. This playback was achieved via speakers placed into an adjacent area of the tank separated by an opaque partition.

During the brief-noise treatments, the noises were only played for 10 seconds during the entire trial (which lasted 5 minutes), while during the prolonged-noise treatments, the noises were played throughout the entire trial.

During each trial, the authors recorded the rate and duration of any general stress-related responses (startles, freezing, hiding), and the total number of Daphnia eaten.  

They also recorded the number of attacks towards food items (typical suction feeding mechanism with binocular fixation, movement towards prey and expansion of the buccal cavity), the number of attacks towards non-food items (attack movement typical of feeding, but directed towards non-food items), and the number of food-handling errors (occasions when a food item was attacked, but not successfully sucked into the mouth, or when food items were spat out and not recaptured).

The authors found that although the sticklebacks showed more startle responses in the presence of noise (in both the brief- and prolonged-noise treatments), the time spent frozen or hiding was not significantly longer when compared to the silent treatments.  

However, they found foraging performance to significantly decrease in the presence of noise, with poorer food discriminating abilities (i.e. a greater number of attacks directed towards non-food items) and poorer food-handling abilities (higher number of food-handling errors) being recorded.  

There was no significant difference in the degradation of foraging performance between the brief- and prolonged-noise treatments, implying that 10 seconds of exposure to noise were enough to disrupt the foraging abilities of the sticklebacks.

According to author Andrew Radford: "Noise pollution is a rapidly increasing issue of global concern, especially underwater. Although lots of research has considered the potential impacts on marine mammals, we know relatively little about how fish are affected, despite their critical importance as a food source for the burgeoning human population. Our study suggests there could be a much wider range of detrimental effects than previously thought, and so there is a vital need for further research."

For more information, see the paper: Purser, J and AN Radford (2011) Acoustic noise induces attention shifts and reduces foraging performance in three-spined sticklebacks (Gasterosteus aculeatus). PLoS ONE 6, e17478. doi:10.1371/journal.pone.0017478