Dredging

About: Dredging is a research topic. Over the lifetime, 3300 publications have been published within this topic receiving 28325 citations.

The effects of fishing on non-target species and habitats: biological, conservation and socio-economic issues

Abstract: Introduction. Acknowledgements. Contributors. PART 1: Distribution of Fishing Effort and Physical Interaction with the Seabed. 1. Spatial and temporal patterns in North Sea fishing effort (S. Jennings, K.J. Warr, S.P.R. Greenstreet and A.J. R. Cotter). 2. Physical impact of beam trawls on seabed sediments (R. Fonteyne). 3. Is bottom traw3ling partly responsible for the regression of Posidonia oceanica meadows in the Mediterranean Sea (G.D. Ardizzone, P. Tucci, A. Somaschini and A. Belluscio). PART 2: Effects of Fishing on Benthic Fauna and Habitats. 4. Fishing mortality of populations of megafauna in sandy sediments (M.J.N. Bergman and J.W. van Santbrink). 5. Effects of otter trawling on the benthos and environment in muddy sediments (B.Ball, B. Munday and I. Tuck). 6. The effects of scallop dredging on gravelly seabed communities (C. Bradsaw, L.O. Veale, A.S. Hill and A.R. Brand). 7. Impact of scallop dredging on maerl grounds (J.M. Hall--Spencer and P.G. Moore). PART 3: Fishing As A Source of Energy Subsidies. 8. The behavioural response of benthic scavengers to otter--trawling disturbance in the Mediterranean (M. Demestre, P. Sanchez and M.J. Kaiser). 9. Food subsidies generated by the beam--trawl fisher in the southern North Sea (M. Fonds and S. Groenewold). 10. Impact of trawling on populations of the invertebrate scavenger Asterias rubens (K. Ramsay, M.J. Kaiser, A.D. Rijnsdorp, J.A. Craeymeersch and J. Ellis). 11. Seabirds and commercial fisheries: population trends of piscivorous seabirds explained (C.J. Camphysen and S. Garthe). PART 4: Long--Term Changes Associated with Fishing. 12. Distribution of macrofauna in relation to the micro--distribution of trawling effort (J.A. Craeymeersch, G.J. Piet, A.D. Rijnsdorp and J. Buijs). 13. Long--term changes in North Sea Benthos: Discerning the role of fisheries (C.L. J. Frid and R.A. Clark). 14. Effects of fishing on non--target fish species (S.P.R. Greenstreet and S.I. Rogers). 15. Impacts of fishing on diversity: from pattern to process (S. Jennings and J.D. Reynolds). PART 5: Conservation Methods, Issues and Implications for Biodiversity. 16. Technical modifications to reduce the by--catches and impacts of bottom--fishing gears (B.van Marlen). 17. Fishing and cetacean by--catches (N.J.C. Tregenza). 18. Effects of fishing on non--targeted species and habitats: identifying key nature conservation issues (M.L. Tasker, P.A. Knapman and D. Laffoley). 19. The need for closed areas as conservation tools (H.J. Lindeboom). 20. No--take zones: a management context (J.W. Horwood). PART 6: Socio--Economic Implications and Mechanisms for Reducing the Impacts of Fisheries. 21. Economic incentives to discard by--catch in unregulated and individual transferable quotas fisheries (S. Pascoe). 22. Options for the reduction of by--catches of harbour porpoises (Phocoena phocoena) in the North Sea (J.M. McGlade and K.I. Metuzals). 23. Economic and sociocultural priorities for marine conservation (P.J. S. Jones). 24. Integrated management: the implications of an ecosystem approach to fisheries management (D. Dymes). PART 7: Workshop Conclusions. 25. The implications of the effects of fishing on non--targeted species and habitats (M.J. Kaiser). Glossary. Index.

Underwater Observations on Tracks of Dredges and Trawls and Some Effects of Dredging on a Scallop Ground

Abstract: Tracks of three types of fishing gear in bottom sediments were observed from a submersible in Chaleur Bay (Gulf of St. Lawrence). Tracks left by past otter trawling activities covered at least 3% of the bottom by area and were considered to have been made by trawl doors.Shallow tracks made by inshore and offshore scallop dredges during the course of the study could be distinguished from each other and from trawl tracks.Scallop dredging lifts fine sediments into suspension, buries gravel below the sand surface, and overturns large rocks embedded in the sediment, appreciably roughening the bottom. The inshore Alberton dredge is inefficient, dumping its contents back onto bottom at intervals during the tow.Dredging causes appreciable lethal and sublethal damage to scallops left in the track, this damage being greatest on rough bottom. Incidental mortalities to scallops with an offshore dredge of at least 13–17% per tow are of the same order of magnitude as estimates of harvesting efficiency made in earlier s...

Effects of scallop dredging on a soft sediment community: a large-scale experimental study

Abstract: Changes to benthic infauna caused by scallop dredging at a site in Port Phillip Bay, southeastern Australia, were examined experimentally using a BACl (before, after, control, impact) design. The experimental dredging was undertaken by commercial fishermen and was typical of normal commercial operations in its spatial extent, intensity and duration Changes to benthic community structure following dredging were monitored using grab samples taken on 3 occasions pre-dredging and 6 occasions post-dredging. The significance of changes was assessed using ANOVA for the more abundant species and, for pooled groups of species, Bray-Curtis community dissimilarities and multidimensional scaling (MDS). The abundance of 7 of the 10 most common species changed significantly (ANOVA p < 0.10) after dredging; 6 species decreased in abundance while 1 species increased. The size and persistence of dredging impacts varied between species, but most species decreased in abundance by 20 to 30%. Dredging impacts became undetectable for most species following their next recruitment. Most species recruited within 6 mo of the dredging impact, but a small number of species still had not recruited after 14 mo. These latter species appeared to cause a persistent change in community structure which was still detectable after 14 mo using Bray-Curtis dissimilarities. MDS ordination indicated that changes to community structure caused by dredging were smaller than those that occur between seasons and years. K E Y WORDS: BACl . Benthic community . Environmental impact . Scallop dredging Fishing Impact

Physical and biological impact of marine aggregate extraction along the French coast of the Eastern English Channel: short- and long-term post-dredging restoration

Abstract: Sediment and associated macrofauna of an industrial extraction site off Dieppe have been monitored during a 10-year period. The original heterogeneous substrate of the shingle bank, characterized by gravels and coarse sands, was progressively dominated by fine sands deposited in dredging tracks. The maximum impact on benthic macrofauna was a reduction by 80% for species richness and 90% for both abundance and biomass. The structure of the community changed from one of coarse sands with Branchiostoma lanceolatum to one of fine sands with Ophelia borealis, Nephtys cirrosa, and Spiophanes bombyx, with local dominance of the opportunistic, sessile Pomatoceros triqueter on bare shingles. Impact of overflowing sands on benthic macrofauna in the surrounding deposition area proved equally large as in the dredged area. Early stages of recolonization were studied from 1995 to 1997 after cessation of dredging. Species richness has been fully restored after 16 months, while densities and biomass were still 40% and 25%, respectively, lower than in reference stations after 28 months. Nevertheless, community structure differed from the initial one corresponding to the new type of sediment. Impact within and around the dredging site was classified according to three levels. Exploration of a former experimental site (CNEXO) dredged in the 1970s provided an example of long-term restoration.