Noisy ships are harming crabs

Last Updated: Wed, Feb 27, 2013 09:00 hrs

London, Feb 27 (IANS) The noise made by ships is producing an ecological side-effect which impacts crabs with the largest specimens being hardest hit, a new study has found.

Crabs exposed to recordings of ship noises showed a higher metabolic rate, indicating elevated stress levels, according to a team from the Universities of Bristol and Exeter.

"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," says Matt Wale, study co-author from Bristol's School of Biological Sciences.

Horseshoe crabs play an important ecological role in the food web. A decline in their numbers will impact shorebirds and sea turtles. Shorebirds depend on exposed crab eggs, but sufficient surface eggs are available only if this species is spawning at high densities, according to a Bristol and Exeter statement.

Similarly, hermit crab act as scavengers. They are omnivorous and known as "aquarium janitors" because they keep a tank free of algae, food debris, dead fish and other organic matter. Hermit crabs are a source of food for fish, birds and other crabs.

Andy Radford, reader in behavioural ecology at Bristol, said: "This is the first indication that there might be different responses to noise depending on the size of an individual."

Steve Simpson from Exeter warned: "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 growth, and quieter farms may be more profitable."

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