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Ecology of Marine SedimentsFrom Science to Management$
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John S. Gray and Michael Elliott

Print publication date: 2009

Print ISBN-13: 9780198569015

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780198569015.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 18 October 2021

Human Impacts on Soft-Sediment Systems—Trawling and Fisheries

Human Impacts on Soft-Sediment Systems—Trawling and Fisheries

(p.122) Chapter 8 Human Impacts on Soft-Sediment Systems—Trawling and Fisheries
Ecology of Marine Sediments

John S. Gray

Michael Elliott

Oxford University Press

Given the discussion above regarding natural changes in the marine benthos, we should now consider the human-mediated (anthropogenic) changes and the response of benthic systems to human impacts. From the 1960s to the 1980s the general opinion seemed to be that pollution (considered in the next chapter) was the most important marine problem, but we now realize that habitat change and habitat loss are of greater concern: see, for example, the Quality Status Report 2000 (OSPAR 2000). One of the greatest effects on the integrity of the seabed and hence its biota is now known to be caused by bed trawling. This has now generated an enormous literature, and the reader is directed to Daans and Eleftheriou (2000) and Hollingworth (2000) for more details. We can take this information and summarize the overall ecosystem effects of fisheries in detailed flow diagrams (referred to as ‘horrendograms’!) to show the interlinked and complex nature of the impact—the effects trawling are included here, but see also those in McLusky and Elliott (2004) (e.g. Fig. 8.1). Historically, the effects of trawling on benthos caused concern as early as 1376 when a petition was made to the English parliament by fishermen concerned over the damage done to the seabed and fisheries by bottom trawling (De Groot 1984). This was despite the gear used by sailing vessels in those days being relatively light and towed at slow speeds and in shallow water only. When steam trawlers were developed in the early 1900s, everything changed. The weight and size of trawls increased and use of tickler chains (mounted on the bottom rope to disturb bottom-living fish upwards and into the trawl net) were of great concern, although studies done in the 1970s to allay the fears of fishermen did not find long-term effects on macrobenthos (Jones 1992). At the end of World War II the otter trawl was developed and its use became widespread. This and the beam trawl (see Fig. 8.4) were (and still are) the types of gear most widely used to fish the seabed.

Keywords:   annelids, bacteria, benthic assemblages, biodiversity, bivalves, coastal systems, conservation, corals, crustaceans, dredging, ecosystems, maerl beds, magelonid polychaetes, megabenthos, rocky shores, sand, scallop dredging, seabeds, shallow water, soft-sediment, species diversity, species numbers, species richness

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