Bottom trawling noise: Are fishing vessels polluting to deeper acoustic habitats?

Eoghan Daly,Martin White

doi:10.1016/j.marpolbul.2020.111877

Eoghan Daly, Martin White

Open Access

https://doi.org/10.1016/j.marpolbul.2020.111877

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Abstract

The impact of bottom trawling noise was quantified on two surrounding marine acoustic habitats using fixed mooring acoustic recorders. Noise during trawling activity is shown to be considerably louder than ambient noise and a nearby underway research vessel. Estimated source levels were above cetacean damage thresholds. Measurements at a submarine canyon indicated potential noise focussing, inferring a role for such features to enhance down slope noise propagation at continental margin sites. Modelled sound propagates more efficiently when sourced from trawling gear dragging along the seabed relative to the vessel as a surface source. Results are contextualised with respect to marine mammal harm, to other anthropogenic ocean noise sources, topography and seasons. Noise energy emitted by bottom trawling activity is a source of pollution that requires further consideration, in line with other pervasive trawling pressures on marine species and seabed habitats, especially in areas of heightened ecological susceptibility.

Highlights

Anthropogenic noise in the ocean is a pervasive and ever-increasing source of pollution encroaching on the natural marine environment
The surface mixed layer, hydrography of the basin consists of East North Atlantic Water (ENAW; Harvey, 1982), above intermediate waters that can include a wedge of Mediterranean Overflow Water (MOW) between 800 and 1200 m (White, 2007) underlain by lower deep waters including Labrador Sea Water and North Atlantic Deep Water (Pollard et al, 1996)
Single value SPLrms values are included for the quietest background noise recorded during the entire survey (112.63 dB re: 1 μPa; 10th June, 15:13 UTC) and for the research vessel Celtic Voyager (117.64 dB re: 1 μPa) at 500 m range from receiver, just prior to mooring recovery

Summary

Introduction

Anthropogenic noise in the ocean is a pervasive and ever-increasing source of pollution encroaching on the natural marine environment. Duncan and McCauley, 2000; McCauley et al, 2000; Nieukirk et al, 2004), drilling (Erbe and McPherson, 2017; MacDonnell, 2017), and pile driving for offshore development (Carstensen et al, 2006; Bailey et al, 2010) These noise sources can be divided into two categories, impulsive and non-impulsive (or continuous) while at relatively close ranges to source (Robinson et al, 2014), each with a differing character of disturbance to the marine environment. Another example is that of bottom trawling, where in addition to vessel noise, heavy trawl gear is dragged along the seabed

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