The Fate of Deep-Sea Coral Reefs on Seamounts in a Fishery-Seascape: What Are the Impacts, What Remains, and What Is Protected?

Alan Williams; Franziska Althaus; Kylie Maguire; Mark Green; Candice Untiedt; Phil Alderslade; Malcolm R. Clark; Nicholas Bax; Thomas A. Schlacher

doi:10.3389/fmars.2020.567002

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The Fate of Deep-Sea Coral Reefs on Seamounts in a Fishery-Seascape: What Are the Impacts, What Remains, and What Is Protected?

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The Fate of Deep-Sea Coral Reefs on Seamounts in a Fishery-Seascape: What Are the Impacts, What Remains, and What Is Protected?

Alan Williams, Franziska Althaus, Kylie Maguire, Mark Green, Candice Untiedt, Phil Alderslade, Malcolm R. Clark, Nicholas Bax and Thomas A. Schlacher

Frontiers in Marine Science, Vol.7, pp.1-22

2020

DOI: https://doi.org/10.3389/fmars.2020.567002

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Abstract

Solenosmilia

scleractinian coral

vulnerable marine ecosystem

towed-camera

indicators

VME

Environmental harm to deep-sea coral reefs on seamounts is widely attributed to bottom trawl fishing. Yet, accurate diagnoses of impacts truly caused by trawling are surprisingly rare. Similarly, comprehensive regional assessments of fishing damage rarely exist, impeding evaluations of, and improvements to, conservation measures. Here we report on trawling impacts to deep-sea scleractinian coral reefs in a regional (10–100s of km) fishery seascape off Tasmania (Australia). Our study was based on 148 km of towed camera transects (95 transects on 51 different seamounts with 284,660 separate video annotations and 4,674 “on-seamount” images analysed), and commercial trawling logbook data indexing fishing effort on and around seamounts. We detect trawling damage on 88% (45 of 51) of seamounts. Conversely, intact deep-sea coral reefs persist in refuge areas on about 39% (20 of 51) of the seamounts, and extend onto rocky seabed adjacent to seamounts. Depth significantly shapes the severity of trawl damage. The most profound impacts are evident on shallow seamounts (those peaking in < 950 m depths) where recent and repeated trawling reduced reefs built by scleractinian corals to rubble, forming extensive accumulations around seamount peaks and flanks. At intermediate depths (∼950–1,500 m), trawling damage is highly variable on individual seamounts, ranging from substantial impacts to no detection of coral loss. Deep seamounts (summit depth > 1,500 m) are beyond the typical operating depth of the trawl fishery and exceed the depth range of living deep-sea coral reefs in the region. Accurately diagnosing the nature and extent of direct trawling impacts on seamount scleractinian coral reefs must use stringent criteria to guard against false positive identifications of trawl impact stemming from either (1) misidentifying areas that naturally lacked deep-sea coral reef as areas where coral had been removed, or (2) attributing trawling as the cause of natural processes of reef degradation. The existence of sizeable deep-sea coral reef refuges in a complex mosaic of spatially variable fishing effort suggests that more nuanced approaches to conservation may be warranted than simply protecting untrawled areas, especially when the biological resources with conservation value are rare in a broader seascape context.

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Title: The Fate of Deep-Sea Coral Reefs on Seamounts in a Fishery-Seascape: What Are the Impacts, What Remains, and What Is Protected?
Authors: Alan Williams (Corresponding Author) - CSIRO Oceans and Atmosphere
Franziska Althaus (Author) - CSIRO Oceans and Atmosphere
Kylie Maguire (Author) - CSIRO Oceans and Atmosphere
Mark Green (Author) - CSIRO Oceans and Atmosphere
Candice Untiedt (Author) - CSIRO Oceans and Atmosphere
Phil Alderslade (Author) - CSIRO Oceans and Atmosphere
Malcolm R. Clark (Author) - National Institute of Water and Atmospheric Research
Nicholas Bax (Author) - CSIRO Oceans and Atmosphere
Thomas A. Schlacher (Author) - University of the Sunshine Coast, Queensland, School of Science and Engineering - Legacy
Publication details: Frontiers in Marine Science, Vol.7, pp.1-22
Publisher: Frontiers Research Foundation
Date published: 2020
DOI: 10.3389/fmars.2020.567002
ISSN: 2296-7745
Copyright note: Copyright © 2020 Williams, Althaus, Maguire, Green, Untiedt, Alderslade, Clark, Bax and Schlacher. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms
Organisation Unit: School of Science and Engineering - Legacy; University of the Sunshine Coast, Queensland; School of Science, Technology and Engineering
Language: English
Record Identifier: 99482297802621
Output Type: Journal article

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