Effects of physical trawling disturbance in a previously unfished sheltered Scottish sea loch

Abstract

The effects of trawling disturbance on a benthic community were investigated with a manipulative field experiment in a fine muddy habitat that has been closed to fishing for over 25 yr. We examined the effects of extensive and repeated experimental trawl disturbance over an 18 mo period on benthic community structure and also followed the subsequent patterns of recovery over a further 18 mo During the penod of trawl disturbance the number of species and individuals increased and measures of diversity (Shannon's exponential H' and S~rnpson's reciprocal D) and evenness decreased in the trawled area relative to the reference site. The cirratulid polychaetes Chaetozone setosa and Caulleriella zetlandica were found to be most resistant to disturbance. whilst the bivalve Nucula nitidosa and polychaetes Scolopolos armiger and Nephtys cirrosa were identified as sensitive species. Multivariate analysis and abundance biomass comparison plots confirmed that community changes occurred following disturbance. with some differences between treatment and reference sites still apparent after 18 mo of recovery. Physical effects, examined with Side-scan and RoxAnn, were identifiable immediately after disturbance, but were almost indistinguishable after 18 mo of recovery. Such long recovery times suggest that even fishing during a restricted period of the year may be sufficient to maintain communities occupying fine muddy sediment habitats in an altered state.

Global analysis of response and recovery of benthic biota to fishing

“…However, it is worth noting that several of the studies reported herein were undertaken in areas that have been closed to fishing (e.g. Tuck et al 1998, Bradshaw et al 2000, Sanchez et al 2000, or in areas that are known from fisheries-enforcement data to experience only limited or no fishing effort (Kaiser & Spencer 1996 or are known to have remained unexploited for reasons such as seabed obstructions (Ball et al 2000). In particular, those studies that have been undertaken in biogenic habitats are very likely to represent the true magnitude of the effects of fishing, as fishing by a commercial fleet would have removed the biogenic habitat and thereby eliminated the possibility of conducting experiments in such a habitat.…”

Long-term (1998 vs. 2010) large-scale comparison of soft-bottom benthic macrofauna composition in the Gulf of Lions, NW Mediterranean Sea

“…Furthermore, A C C E P T E D M A N U S C R I P T Rosenberg et al (2003) highlighted the presence of trawls tracks in both regions (southwestern and eastern) of the Gulf of Lions. Trawling is known to directly affect macrobenthic communities, leading to the loss of epifauna, the smoothing of sedimentary bed forms and the reduction of bottom roughness (Tuck et al, 1998).…”

Using fish stomachs as samplers of the benthos: integrating long-term and broad scales

“…Thrush et al 1995, Jennings & Polunin 1996, Kaiser & Spencer 1996, Collie et al 1997, Engel & Kvitek 1998, Tuck et al 1998, Auster & Langton 1999, Ball et al 2000, Hall-Spencer & Moore 2000. However, the effects are less clear at broader scales and for chronic disturbances of the ocean bottom (Kaiser 1998(Kaiser , 2003.…”