Viewpoint On effects of trawling, benthos and sampling design John S. Gray a, * , Paul Dayton b , Simon Thrush c , Michel J. Kaiser d a Marine Biodiversity Research Program, Department of Biology, University of Oslo, P.O. Box 1066 Blindern, 0316 Oslo, Norway b Scripps Institution of Oceanography, UCSD, 9500, Gilman Drive, La Jolla, CA 92093-0227, USA c National Institute for Water and Atmospheric Research, P.O. Box 11-115 Hamilton, New Zealand d School of Ocean Sciences, University of Wales-Bangor, Menai Bridge LL59 5AB, UK Abstract The evidence for the wider effects of fishing on the marine ecosystem demands that we incorporate these considerations into our man- agement of human activities. The consequences of the direct physical disturbance of the seabed caused by towed bottom-fishing gear have been studied extensively with over 100 manipulations reported in the peer-reviewed literature. The outcome of these studies varies according to the gear used and the habitat in which it was deployed. This variability in the response of different benthic systems concurs with established theoretical models of the response of community metrics to disturbance. Despite this powerful evidence, a recent FAO report wrongly concludes that the variability in the reported responses to fishing disturbance mean that no firm conclusion as to the effects of fishing disturbance can be made. This thesis is further supported (incorrectly) by the supposition that current benthic sampling methodologies are inadequate to demonstrate the effects of fishing disturbance on benthic systems. The present article addresses these two erroneous conclusions which may confuse non-experts and in particular policy-makers. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Benthic trawling; Dredging; Fisheries impacts; Benthic disturbance; BACI design; Statistical errors; Benthic disturbance A few years ago Watling and Norse produced their famous paper where they likened effects of trawling to clear-cutting of virgin forest (Watling and Norse, 1998). This was followed in 2003 by a large ICES Symposium focussed on the topic of ‘‘Marine Benthos Dynamics: Envi- ronmental and Fisheries Impacts’’, Eleftheriou, 2000). Comprehensive reviews (Thrush and Dayton, 2002; Kaiser et al., 2006) and many other papers lead to the overwhelm- ing conclusion that trawling has had negative effects on benthic habitats and species. In commenting on the degra- dation of coastal areas and their resources the United Nations Environment Programme, GEO2000 global environmental outlook, notes that resource exploitation, changes to habitats and disruption of ecosystem functions probably pose more serious threats to many marine and coastal areas than pollution (http://www.unep.org/ geo2000/english/0223.htm). Furthermore, the recent Millennium Assessment (http://www.millenniumassessment. org/en/index.aspx) also highlights the role of fishing in degradation of the marine environment. Yet now the back- lash appears! The United Nation’s Food and Agriculture Organisation commissioned and published a review of the impacts of trawling and scallop dredging on benthic habitats and communities (Løkkeberg, 2005). The main conclusion of this report (p. 47) is that, ‘‘It is difficult to conduct impact studies leading to clear and unambiguous conclusions because knowledge of the complexity and nat- ural variability of benthic communities is rudimentary’’. The review speculates further on the utility of grabs and box-corers as sampling tools (p. 9) stating that ‘‘these methods are not suitable for sampling benthic fauna with patchy distribution and low abundance.’’ These worrying assertions reflect a profound ignorance of an abundant literature and could lead to inappropriate conclusions by a non-expert reader. The author of the FAO report does not seem to know that benthic assemblages globally are the most widely used 0025-326X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2006.07.003 * Corresponding author. Fax: +47 228 54438. E-mail address: j.s.gray@bio.uio.no (J.S. Gray). www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 52 (2006) 840–843