Sitting at the dock of the bay you might hear the crash of breaking waves and squawking seagulls flying overhead. As you take in all the sites and sounds, you next hear a speeding boat racing by and an oil tanker a mile away. Grinding engine noises and long, low, horn sounds can be deafening in any harbor. And while you can handle it for the hour or two you spend there, the continuous sounds of these noisy vessels are being found to have repercussions on marine life.
Sitting at the dock of the bay you might hear the crash of breaking waves and squawking seagulls flying overhead. As you take in all the sites and sounds, you next hear a speeding boat racing by and an oil tanker a mile away. Grinding engine noises and long, low, horn sounds can be deafening in any harbor. And while you can handle it for the hour or two you spend there, the continuous sounds of these noisy vessels are being found to have repercussions on marine life.
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A study published in Biology Letters found that ship noise can affect the metabolism of certain crab species, with largest crabs faring the worst.
A team from the Universities of Bristol and Exeter found that crabs exposed to recordings of ship noise showed an increase in metabolic rate, indicating elevated stress. Consequently, this could have implications for growth and, if the metabolic cost of noise causes crabs to spend more time foraging to compensate, it could also lead to an increased risk of predation.
Researcher Matt Wale from Bristol's School of Biological Sciences describes the study: "We used controlled experiments to consider how shore crabs of different sizes respond to both single and repeated exposure to playback of ship noise. Ship noise is the most common source of noise in the aquatic environment."
Dr Andy Radford, Reader in Behavioural Ecology at Bristol explains: "We found that the metabolic rate of crabs exposed to ship noise was higher than those experiencing ambient harbour noise, and that larger individuals were affected most strongly. This is the first indication that there might be different responses to noise depending on the size of an individual."
Unfortunately, researchers found little evidence that crabs will get used to or acclimate to the noise over time.
If commercially important shellfish are affected by noise, these findings have implications for fisheries in busy shipping areas where larger individuals may be affected. Conversely, if reducing noise reduces metabolic costs, then reducing noise levels in aquaculture facilities may lead to higher yields.
Dr Steve Simpson from the University of Exeter warned: "Since larger crabs are affected more strongly by noise this could have implications for fisheries in noisy areas. Also, many crustacean species, particularly prawns, are grown in aquaculture, so if acoustic disturbance has a metabolic cost then operational noise in farms may impact on growth, and quieter farms may be more profitable."
Read more at Bristol University.
Crab image via Shutterstock.
