Deep-sea benthic habitats and the impacts of trawling on them in the offshore Greenland halibut fishery, Davis Strait, west Greenland

Stephen Long,Karl Zinglersen,Rasmus Nygaard,Nanette Hammeken Arboe,Mona Fuhrmann,Michael Darling,Chris Yesson,Kirsty M Kemp,Martin E Blicher,Silvana Birchenough

doi:10.1093/icesjms/fsab148

Abstract

Abstract The offshore Greenland halibut (Reinhardtius hippoglossoides) fishery, west Greenland, employs demersal trawl gear at depths of 800–1400 m. In contrast to many deep-sea fisheries, the target stock appears stable and the fishery is of significant economic importance. Recent Marine Stewardship Council certification of this fishery highlighted the paucity of knowledge of benthic habitats and trawling impacts, which this study aimed to address using a towed benthic video sled. The spatially discrete northern and southern areas of the fishery were found to be distinct in terms of the communities present, which non-metric multidimensional scaling suggests is primarily driven by temperature. Extensive physical evidence of trawling was observed. Trawling effort was significantly linked with community composition, with a negative association between trawling effort and abundance of some taxa, including some vulnerable marine ecosystem (VME) indicator species. Three potential VMEs are identified: (i) Flabellum alabastrum cup coral meadows; (ii) a Halipteris finmarchica sea pen field; and (iii) areas exhibiting mixed assemblages of VME indicators. Of immediate conservation concern is a H. finmarchica field, which seems to be at least regionally rare, is situated within the fringes of existing trawling effort and is currently afforded no protection by management measures.

Highlights

Declines in shallow water stocks and improving technology have led to the expansion of deep-sea fisheries in recent decades (Morato et al, 2006)
In the previous Environmental Impact Assessments (EIAs), Non-metric multidimensional scaling (NMDS) of community data obtained by grab sampling, showed clear differentiation between the community in the Eqqua block and the Lady Franklin and Atammik blocks (BSL, 2011b), which concurs with the findings here
This study identifies three candidate vulnerable marine ecosystem (VME): (i) F. alabastrum cup coral meadows; (ii) H. finmarchica sea pen fields; and (iii) a mixed assemblage of VME indicator taxa

Summary

Introduction

Declines in shallow water stocks and improving technology have led to the expansion of deep-sea fisheries in recent decades (Morato et al, 2006). The sustainability of deep-sea fisheries has been repeatedly questioned, both in terms of the impacts on the target stock and the wider ecosystem Clark’s Law, coined by Norse et al (2012), observes that where commercial deep-sea species are abundant, the combination of high biomass and low productivity creates a strong economic incentive to maximise catches in the short-term rather than sustainably exploit stocks over. C International Council for the Exploration of the Sea 2021.

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