Right to Quiet Society Noiseletter
Spring 2015, page 2

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Boat noise stops fish finding home

Boat noise disrupts orientation behaviour in larval coral reef fish, according to new research from the Universities of Bristol, Exeter and Liège. Reef fish are normally attracted by reef sound but the study, conducted in French Polynesia, found that fish are more likely to swim away from recordings of reefs when boat noise is added.

Sophie Holles, a PhD researcher at the University of Bristol and one of the study's authors, said: "Natural under­water sound is used by many animals to find suitable habitat, and traffic noise is one of the most widespread pollutants. If settlement is disrupted by boat traffic, the resilience of habitats like reefs could be affected."

Sound travels better underwater than in air and reefs are naturally noisy places: fish and invertebrates produce feeding and territorial sounds while wind, waves and cur­rents create other background noise. Boats can be found around all coastal environments where people live and the noise they make spreads far and wide. Co­-author, Dr Steve Simpson, a marine biologist at the University of Exeter, said:

"Boat noise may scare fish, af­fecting their ecology. Since one in five people in the world rely on fish as their major source of protein, regulating traffic noise in important fisheries areas could help marine communities and the people that depend on them."

The study used controlled field experiments with settlement stage coral reef fish larvae. Larvae in a long plastic tube could decide to swim towards or away from a speak­er playing back different sounds. In ambient noise equal numbers of fish were found in each section of the tube and in reef noise most fish swam towards the sound. But when boat noise was played along with reef noise, more fish swam away from the sound than in reef noise alone.

Co­author, Dr. Andy Radford from the University of Bristol, said: "This is the first indication that noise pollution can affect orientation behaviour during the critical settle­ment stage. Growing evidence for the impact of noise on fish suggests that consideration should be given to the regulation of human activities in protected areas."

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Ship noise makes crabs get crabby

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. In the real world this could have implications for growth and, if the metabolic cost of noise causes crabs to spend more time foraging to compensate, could also increase the 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."

Explains Dr. Andy Radford, Reader in Behavioural Ecology at Bristol: "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."

If commercially important crabs and lobsters are affected by noise, these findings have implications for fisheries in busy shipping areas where large individuals may be los­ing out. Conversely, if reducing noise reduces metabolic costs, then quietening 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."

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Noisy icebergs

Atmospheric and surface ocean temperatures in the Antarctic Peninsula region have increased by a few degrees Celsius over the last few decades, and they are the most rapid changes recorded in the Southern Hemisphere during this time period (Cook et al., 2005; Meredith and King, 2005). Associated with this ongoing warming are ice­sheet breakup, iceberg calving, and subsequent iceberg grounding that are accompanied by the release of acous­tic energy into the Southern Ocean.

Although much attention has been given to the increasing anthropogenic contributions to ocean noise, which may be as much as 12 dB over the last few decades (Hilde­brand, 2009), the sounds created by ice breakup at the poles may represent an under appreciated, yet signifi­cant, natural contribution to the ocean noise budget. (First paragraph)

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