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1
Jones, Peter. "The spread of bottom trawling in the British Isles, c.1700–1860." International Journal of Maritime History 30, no. 4 (November 2018): 681–700. http://dx.doi.org/10.1177/0843871418804486.
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Widespread bottom trawling in British waters has traditionally been dated from the last decades of the 18th century, and its early heartland has most commonly been identified as the Torbay area of Devon. This article shows that, in fact, by the time Torbay became known as a centre for the industry, bottom trawling was already well-known and relatively widespread around much of England and Wales, as well as large parts of Eastern and Southern Ireland. Following on from an earlier contribution in this journal, it also demonstrates that bottom trawling’s unbroken history, going back to at least the first decades of the 17th century, has always been beset by controversy, but that the middle decades of the 19th century saw a sea-change in official attitudes that, in effect, ushered in an era of unfettered expansion in industrial beam trawling by the 1890s.
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Bergman, Magda J. N., and Erik H. Meesters. "First indications for reduced mortality of non-target invertebrate benthic megafauna after pulse beam trawling." ICES Journal of Marine Science 77, no. 2 (January 17, 2020): 846–57. http://dx.doi.org/10.1093/icesjms/fsz250.
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Abstract Two alternative stimulation techniques to reduce mortality in benthic megafauna were tested relative to standard tickler chain beam trawling: longitudinal electrodes (pulse trawl) and longitudinal chains. Longitudinal chains caused higher mortality than pulse trawling in 3 species. Standard trawling gave higher mortality in Echinocardium cordatum than pulse trawling. Between longitudinal chain and standard trawling were no significant differences. This trend in decreasing mortality from longitudinal, to standard and then pulse trawling was confirmed by a similar decline in: i) numbers of significant species mortalities per trawl type, ii) average mortalities, i.e. longitudinal chain caused 41% more mortality than standard trawling and pulse trawling 43% less, iii) pre- and post-trawling community dissimilarities. A significant majority of species showed higher mortalities after longitudinal than after standard trawling and, conversely, lower mortalities after pulse trawling. Trawls with longitudinal chains instead of cross tickler chains increase megafaunal impact. On the contrary, pulse trawling can reduce the impact, although average mortality remains substantial (25%) even in impoverished benthic test assemblages in the southern North Sea. Power, generally was low and reference areas, free of (pulse) trawling, and inhabited by more vulnerable taxa will facilitate higher powered studies on the impact of standard and alternative trawling techniques.
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Rijnsdorp, A. D., J. G. Hiddink, P. D. van Denderen, N. T. Hintzen, O. R. Eigaard, S. Valanko, F. Bastardie, et al. "Different bottom trawl fisheries have a differential impact on the status of the North Sea seafloor habitats." ICES Journal of Marine Science 77, no. 5 (April 24, 2020): 1772–86. http://dx.doi.org/10.1093/icesjms/fsaa050.
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Abstract Fisheries using bottom trawls are the most widespread source of anthropogenic physical disturbance to seafloor habitats. To mitigate such disturbances, the development of fisheries-, conservation-, and ecosystem-based management strategies requires the assessment of the impact of bottom trawling on the state of benthic biota. We explore a quantitative and mechanistic framework to assess trawling impact. Pressure and impact indicators that provide a continuous pressure–response curve are estimated at a spatial resolution of 1 × 1 min latitude and longitude (∼2 km2) using three methods: L1 estimates the proportion of the community with a life span exceeding the time interval between trawling events; L2 estimates the decrease in median longevity in response to trawling; and population dynamic (PD) estimates the decrease in biomass in response to trawling and the recovery time. Although impact scores are correlated, PD has the best performance over a broad range of trawling intensities. Using the framework in a trawling impact assessment of ten métiers in the North Sea shows that muddy habitats are impacted the most and coarse habitats are impacted the least. Otter trawling for crustaceans has the highest impact, followed by otter trawling for demersal fish and beam trawling for flatfish and flyshooting. Beam trawling for brown shrimps, otter trawling for industrial fish, and dredging for molluscs have the lowest impact. Trawling is highly aggregated in core fishing grounds where the status of the seafloor is low but the catch per unit of effort (CPUE) per unit of impact is high, in contrast to peripheral grounds, where CPUE per unit of impact is low.
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Hanna, Jack, Seán Power, Phil O'Keeffe, and Mary Ryan. "Trawling the Past." Books Ireland, no. 194 (1996): 93. http://dx.doi.org/10.2307/20623248.
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Nuwer, Rachel. "Trawling for Viruses." Scientific American 313, no. 6 (November 17, 2015): 34. http://dx.doi.org/10.1038/scientificamerican1215-34a.
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Warren, Graham. "Trawling for receptors." Nature 346, no. 6282 (July 1990): 318–19. http://dx.doi.org/10.1038/346318b0.
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Gregg, J. Marty, and Amit Kumar. "Trawling for complements." Nature 510, no. 7506 (June 2014): 481–82. http://dx.doi.org/10.1038/510481a.
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Hinz, Hilmar, Jan G. Hiddink, James Forde, and Michel J. Kaiser. "Large-scale responses of nematode communities to chronic otter-trawl disturbance." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 4 (April 1, 2008): 723–32. http://dx.doi.org/10.1139/f08-002.
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Nematodes, because of their small size and short life cycles, are thought to be less affected by direct trawling mortality compared with the larger macrofauna. However, nematodes may still be indirectly affected by the physical disturbance of trawling through changing sediment characteristics and food web structure. We determined whether nematode communities on two muddy fishing grounds located in the North Sea and Irish Sea were affected by chronic otter-trawl disturbance and quantified these effects. Nematode abundance, production, and genus richness declined in response to trawling within both areas. Nematode biomass did not respond to trawling intensity. Genus composition was affected by trawling only in the North Sea. The responses in abundance of individual nematode genera to increasing trawling intensity were negative as well as positive. These results indicate that despite their size and fast life cycle, nematodes are affected by intensive trawling on muddy fishing grounds. The loss in secondary production from nematodes can have far-reaching consequences for the integrity of the benthic food web. As bottom trawl fisheries are expanding into ever deeper muddy habitats, the results presented here are an important step towards understanding the global ecosystem effects of bottom trawling.
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Mills, Craig M., Sunny E. Townsend, Simon Jennings, Paul D. Eastwood, and Carla A. Houghton. "Estimating high resolution trawl fishing effort from satellite-based vessel monitoring system data." ICES Journal of Marine Science 64, no. 2 (December 14, 2006): 248–55. http://dx.doi.org/10.1093/icesjms/fsl026.
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Abstract Mills, C. M., Townsend, S. E., Jennings, S., Eastwood, P. D., and Houghton, C. A. 2007. Estimating high resolution trawl fishing effort from satellite-based vessel monitoring system data. – ICES Journal of Marine Science, 64: 248–255. High resolution estimates of trawling effort are needed to underpin studies of trawling impacts on species, habitats, and ecosystem processes, and to monitor responses to area closure and other management actions. Satellite-based vessel monitoring systems (VMS) were designed for fishery control and enforcement, but they provide potentially valuable source information on spatial and temporal patterns of trawling activity at multiple scales. Based on an analysis of VMS data for UK beam trawlers in the North Sea, a method is described for identifying trawling activity and estimating fishing intensity based on the minimum and maximum potential spatial extent of trawling effort from VMS data. The optimal method for identifying trawling and steaming behaviour combined speed and directionality rules and correctly identified trawling and steaming in 99% and 95% of cases, respectively. Using speed- and directionality-filtered VMS data, trawling effort can be reported as area impacted per unit time per unit area at a range of grid scales from 1 km to 100 km (10 000 km2). Trawling effort is accurately represented at a grid cell resolution of 3 km or less.
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Kenchington, E. LR, J. Prena, K. D. Gilkinson, D. C. Gordon Jr., K. MacIsaac, C. Bourbonnais, P. J. Schwinghamer, T. W. Rowell, D. L. McKeown, and W. P. Vass. "Effects of experimental otter trawling on the macrofauna of a sandy bottom ecosystem on the Grand Banks of Newfoundland." Canadian Journal of Fisheries and Aquatic Sciences 58, no. 6 (June 1, 2001): 1043–57. http://dx.doi.org/10.1139/f01-053.
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A 3-year otter trawling experiment was conducted on a deepwater (120146 m) sandy bottom ecosystem on the Grand Banks of Newfoundland that had not experienced trawling for at least 12 years. The benthic macrofauna were sampled before and after trawling and in reference areas. The 200 grab samples collected contained 246 taxa, primarily polychaetes, crustaceans, echinoderms, and molluscs. Biomass was dominated by propeller clams (Cyrtodaria siliqua) and sand dollars (Echinarachnius parma), while abundance was dominated by the polychaete Prionospio steenstrupi and the mollusc Macoma calcarea. The most prominent feature of the data was a natural decline in the total number of species, the total abundance, and the abundance and biomass of selected species between 1993 and 1995. The only immediate effect of trawling was seen in 1994 when the abundance of 13 species, the biomass of 11 species (mostly polychaetes), and the total abundance per grab were significantly lower. There was little evidence of long-term trawling effects. When trawling disturbance was indicated, it appeared to mimic natural disturbance, shifting the community in the same direction in multidimensional scaling ordination; no distinctive trawling signature was observed. However, the results of this experiment should not be uncritically extrapolated to the impacts of commercial trawling.
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Tanner, Jason E. "The influence of prawn trawling on sessile benthic assemblages in Gulf St. Vincent, South Australia." Canadian Journal of Fisheries and Aquatic Sciences 60, no. 5 (May 1, 2003): 517–26. http://dx.doi.org/10.1139/f03-044.
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Most experimental studies on the effects of trawling on the benthos use remote sampling techniques and are conducted in recently trawled areas. Thus it is difficult to determine the effects of trawling on previously unfished areas, and the fates of individual animals cannot be followed. In this study, I follow the fates of individuals of several sessile taxa when exposed to experimental trawling in areas that have not been trawled for some 1520 years. Although there was a significant trawling by location effect for all multivariate analyses and most individual taxa, I found that trawling had an overall negative effect on the benthos. Epifauna at trawled sites decreased in abundance by 28% within 2 weeks of trawling and by another 8% in the following 23 months (compared with control sites). Seasonal seagrasses were also less likely to colonise trawled sites than untrawled sites. The persistence of most taxa declined significantly in trawled areas compared with untrawled areas. In contrast to this, the recruitment rates of several taxa into visible size classes increased after trawling, presumably because of a reduction in competition.
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van Denderen, P. Daniël, Niels T. Hintzen, Tobias van Kooten, and Adriaan D. Rijnsdorp. "Temporal aggregation of bottom trawling and its implication for the impact on the benthic ecosystem." ICES Journal of Marine Science 72, no. 3 (October 21, 2014): 952–61. http://dx.doi.org/10.1093/icesjms/fsu183.
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Abstract Understanding trawling impacts on the benthic ecosystem depends to a large extent on the ability to estimate trawling activity at the appropriate scale. Several studies have assessed trawling at fine spatial scales yearly, largely ignoring temporal patterns. In this study, we analysed these temporal patterns in beam trawl effort intensity at 90 stations of the Dutch continental shelf of the North Sea for a period of 10 years, at a fine temporal (weekly) and spatial (110 × 70 m) scale using Vessel Monitoring by Satellite (VMS) data. Our results show that trawling is aggregated in time and shows clear seasonality, related to the behavior of the fleet and migration patterns of the target fish species. The temporal patterns affect the overall impact on and the recovery of the benthic community, as is illustrated with a benthic population model. Our results imply that trawling impact studies using high-resolution data like VMS should take account of the possibility of temporal aggregation and seasonality in trawling to improve the assessment of the impact of trawling on the population dynamics of benthos.
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Jones, Peter. "The long ‘lost’ history of bottom trawling in England, c.1350–1650." International Journal of Maritime History 30, no. 2 (May 2018): 201–17. http://dx.doi.org/10.1177/0843871418766765.
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This article considers the early history of bottom trawling in England. It demonstrates that trawling – and, in particular, beam trawling – has a very long history stretching back to at least the fourteenth century. Over the following two centuries it spread from the Thames Estuary along the south and south-east coasts, and by 1600 its use was widespread and it was being pursued some distance from shore. The article also shows that bottom trawling has always been a controversial practice, and that by the early modern period it was highly unpopular, not only among non-trawling fishermen (who viewed it as a threat to their livelihood), but with many in positions of power who sought to limit and even prohibit its use. Finally, the article considers the contemporary significance of this newly exposed history, given that historical complaints about bottom trawling were framed in remarkably similar terms to those used by its modern opponents.
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Jac, Cyrielle, Nicolas Desroy, Jean-Claude Duchêne, Aurélie Foveau, Céline Labrune, Lyvia Lescure, and Sandrine Vaz. "Assessing the impact of trawling on benthic megafauna: comparative study of video surveys vs. scientific trawling." ICES Journal of Marine Science 78, no. 5 (April 16, 2021): 1636–49. http://dx.doi.org/10.1093/icesjms/fsab033.
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Abstract Most studies about benthic community use small-scale sampling methods focused on the infauna such as grabs or box-corers. The benthic data collected by scientific trawl surveys in all European waters, in the frame of the Common Fishery Policy Data Collection Multiannual Program, can be used to study the impact of large-scale fisheries such as trawling. However, the catchability of trawls is very dependent on the nature of the seabed as well as resulting ground-gear adaptations. Due to its non-destructive nature and its ability to focus on benthic macro-epifauna, towed video sampling appears to be a good alternative to monitor the impact of trawling on benthic communities. In the present work, we studied the influence of fishery induced seabed abrasion and video characteristics on nine indices, which can be used to monitor the effect of trawling on benthic communities, was studied. Among them, three indices specific to fishery effect detection based on biological traits appeared to be the best performing benthic indices with video data: modified-Trawling Disturbance Index, partial-Trawling Disturbance Index, and modified sensitivity index. The effectiveness of these indices to monitor the effect of trawling was evaluated and compared between trawl and video sampling. This work has highlighted that video sampling could be a good alternative, or at least a complementary method, to scientific trawling to monitor the effect of trawling on benthic communities in European waters.
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Duplisea, Daniel E., Simon Jennings, Karema J. Warr, and Tracy A. Dinmore. "A size-based model of the impacts of bottom trawling on benthic community structure." Canadian Journal of Fisheries and Aquatic Sciences 59, no. 11 (November 1, 2002): 1785–95. http://dx.doi.org/10.1139/f02-148.
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Bottom trawling causes widespread disturbance to the sediments in shallow-shelf seas. The resultant mortality of benthic fauna is strongly size dependent. We empirically demonstrate that beam trawling frequency in the central North Sea had a greater effect on fauna size distribution in a soft sediment benthic community than variables such as sediment particle size and water depth. Accordingly, we simulated the impacts of trawling disturbance on benthos using a model consisting of 37 organism size classes between 1 μg and 140 g wet weight. The model produced a productionbiomass versus size relationship consistent with published studies and allowed us to predict the impacts of trawling frequency on benthos size distributions. Outputs were consistent with empirical data; however, at high yet realistic trawling frequencies, the model predicted an extirpation of most macrofauna. Empirical data show that macrofauna persist in many heavily trawled regions; therefore, we suggest that trawling by real fisheries is sufficiently heterogeneous to provide spatial refuges less impacted by trawling. If correct, our analyses suggest that fishery management measures that do not reduce total effort but do lead to effort displacement and spatial homogenization (e.g., temporarily closed areas) may have adverse effects on the systemic persistence of intermediate- and large-sized macrofauna.
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Sheppard, Charles. "Trawling the sea bed." Marine Pollution Bulletin 52, no. 8 (August 2006): 831–35. http://dx.doi.org/10.1016/j.marpolbul.2006.07.002.
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Purvis, Mark. "Trawling for pump information." World Pumps 1995, no. 348 (September 1995): 3. http://dx.doi.org/10.1016/s0262-1762(99)80910-9.
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Ash, C. "MICROBIOLOGY: Trawling Hidden Waters." Science 321, no. 5892 (August 22, 2008): 1021c. http://dx.doi.org/10.1126/science.321.5892.1021c.
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Reichhardt, Tony. "Trawling through the wreckage." Nature 426, no. 6968 (December 2003): 754–55. http://dx.doi.org/10.1038/426754b.
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Choudhri, Asim F., and Thomas M. Carr. "Who’s Trawling Our Waters?" Journal of the American College of Radiology 5, no. 4 (April 2008): 538–39. http://dx.doi.org/10.1016/j.jacr.2007.09.008.
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Killen, Shaun S., Julie J. H. Nati, and Cory D. Suski. "Vulnerability of individual fish to capture by trawling is influenced by capacity for anaerobic metabolism." Proceedings of the Royal Society B: Biological Sciences 282, no. 1813 (August 22, 2015): 20150603. http://dx.doi.org/10.1098/rspb.2015.0603.
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The harvest of animals by humans may constitute one of the strongest evolutionary forces affecting wild populations. Vulnerability to harvest varies among individuals within species according to behavioural phenotypes, but we lack fundamental information regarding the physiological mechanisms underlying harvest-induced selection. It is unknown, for example, what physiological traits make some individual fish more susceptible to capture by commercial fisheries. Active fishing methods such as trawling pursue fish during harvest attempts, causing fish to use both aerobic steady-state swimming and anaerobic burst-type swimming to evade capture. Using simulated trawling procedures with schools of wild minnows Phoxinus phoxinus , we investigate two key questions to the study of fisheries-induced evolution that have been impossible to address using large-scale trawls: (i) are some individuals within a fish shoal consistently more susceptible to capture by trawling than others?; and (ii) if so, is this related to individual differences in swimming performance and metabolism? Results provide the first evidence of repeatable variation in susceptibility to trawling that is strongly related to anaerobic capacity and swimming ability. Maximum aerobic swim speed was also negatively correlated with vulnerability to trawling. Standard metabolic rate was highest among fish that were least vulnerable to trawling, but this relationship probably arose through correlations with anaerobic capacity. These results indicate that vulnerability to trawling is linked to anaerobic swimming performance and metabolic demand, drawing parallels with factors influencing susceptibility to natural predators. Selection on these traits by fisheries could induce shifts in the fundamental physiological makeup and function of descendent populations.
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De Robertis, Alex, and Christopher D. Wilson. "Walleye pollock respond to trawling vessels." ICES Journal of Marine Science 63, no. 3 (January 1, 2006): 514–22. http://dx.doi.org/10.1016/j.icesjms.2005.08.014.
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Abstract The potential for fish to avoid survey vessels is a major source of uncertainty in stock-assessment surveys. Although walleye pollock (Theragra chalcogramma) are the subject of a substantial commercial fishery in the North Pacific, their behavioural responses to approaching survey vessels remain poorly understood. As a first step in an effort to determine if walleye pollock avoid survey vessels engaged in trawling operations, we made pairwise comparisons of acoustic backscatter recorded by survey vessels while free-running and while trawling. Results are presented of acoustic backscatter recorded from NOAA's RV “Miller Freeman”, which used a midwater trawl during the 1996–2002 eastern Bering Sea surveys, and a chartered commercial fishing vessel, which used a bottom trawl during a survey in 2003 in the Gulf of Alaska. In both cases, average backscatter from a vessel-mounted echosounder was significantly higher when free-running than when trawling. These decreases in backscatter are consistent with increased vessel avoidance while trawling. There were no differences in the vertical distribution of backscatter when free-running and trawling, indicating that pollock do not exhibit elevated diving responses when approached by a trawling vessel rather than by a free-running vessel. Although the study indicates that pollock respond to trawling vessels, the nature of the behavioural response cannot be determined with the methods used in this study. Future work should evaluate potential stimuli produced by trawlers to which pollock may react, and should document changes in behaviour that may occur in their presence.
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Simpson, Anne W., and Les Watling. "An investigation of the cumulative impacts of shrimp trawling on mud-bottom fishing grounds in the Gulf of Maine: effects on habitat and macrofaunal community structure." ICES Journal of Marine Science 63, no. 9 (January 1, 2006): 1616–30. http://dx.doi.org/10.1016/j.icesjms.2006.07.008.
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Abstract The cumulative impacts (i.e. collective, multi-year effects) of seasonal commercial shrimp trawling on habitat and macrofaunal community structure were investigated for two mud-bottom fishing grounds and adjacent untrawled areas in the Gulf of Maine. Habitat structure on mud-bottom fishing grounds did not differ significantly from that in similar untrawled areas. Moreover, sediment resuspension associated with shrimp trawling did not appear to result in net loss of deposited material on fishing grounds, but there is evidence that trawling may alter sediment mixing regimes. Visual inspection of the sediment surface in trawled areas revealed minimal evidence of fishing gear disturbance (such as door, bobbin, or net marks), but biological disturbance features, including numerous large burrows, pits, and dense aggregations of the brittle star Ophiura sarsi, were present in both trawled and untrawled areas. Macrofaunal communities on the two fishing grounds exhibited different responses to shrimp trawling, which were attributed to disparities in levels of fishing activity during the 2000–2001 shrimp season. The results suggest that seasonal shrimp trawling produced at least short-term changes (<3 months) in macrofaunal community structure, but did not appear to result in long-term cumulative changes. Resilience to trawling disturbance may be due in part to high levels of biological disturbance generated by benthic megafauna, such as lobsters and fish. By burrowing, pit-digging, and possibly foraging, these animals rework sediments to a depth of 16–17 cm, creating a natural level of disturbance that appears to maintain macrofaunal communities in a perpetually low successional state, so potentially minimizing trawling impacts.
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Hiddink, Jan Geert, Simon Jennings, Marija Sciberras, Claire L. Szostek, Kathryn M. Hughes, Nick Ellis, Adriaan D. Rijnsdorp, et al. "Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance." Proceedings of the National Academy of Sciences 114, no. 31 (July 17, 2017): 8301–6. http://dx.doi.org/10.1073/pnas.1618858114.
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Bottom trawling is the most widespread human activity affecting seabed habitats. Here, we collate all available data for experimental and comparative studies of trawling impacts on whole communities of seabed macroinvertebrates on sedimentary habitats and develop widely applicable methods to estimate depletion and recovery rates of biota after trawling. Depletion of biota and trawl penetration into the seabed are highly correlated. Otter trawls caused the least depletion, removing 6% of biota per pass and penetrating the seabed on average down to 2.4 cm, whereas hydraulic dredges caused the most depletion, removing 41% of biota and penetrating the seabed on average 16.1 cm. Median recovery times posttrawling (from 50 to 95% of unimpacted biomass) ranged between 1.9 and 6.4 y. By accounting for the effects of penetration depth, environmental variation, and uncertainty, the models explained much of the variability of depletion and recovery estimates from single studies. Coupled with large-scale, high-resolution maps of trawling frequency and habitat, our estimates of depletion and recovery rates enable the assessment of trawling impacts on unprecedented spatial scales.
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MÉRILLET, LAURÈNE, MAUD MOUCHET, MARIANNE ROBERT, MICHÈLE SALAÜN, LUCIE SCHUCK, SANDRINE VAZ, and DOROTHÉE KOPP. "Using underwater video to assess megabenthic community vulnerability to trawling in the Grande Vasière (Bay of Biscay)." Environmental Conservation 45, no. 2 (October 16, 2017): 163–72. http://dx.doi.org/10.1017/s0376892917000480.
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SUMMARYTrawling activities are considered to be one of the main sources of disturbance to the seabed worldwide. We aimed to disentangle the dominance of environmental variations and trawling intensity in order to explain the distribution of diversity patterns over 152 sampling sites in the French trawl fishing-ground, the Grande Vasière. Using a towed underwater video device, we identified 39 taxa to the finest taxonomic level possible, which were clustered according to their vulnerability to trawling disturbance based on functional traits. Using generalized linear models, we investigated whether the density distribution of each vulnerability group was sensitive to trawling intensity and habitat characteristics. Our analyses revealed a structuring effect of depth and substratum on community structure. The distribution of the more vulnerable group was a negative function of trawling intensity, while the distributions of the less vulnerable groups were independent of trawling intensity. Video monitoring coupled with trait-based vulnerability assessment of macro-epibenthic communities might be more relevant than the traditional taxonomic approach to identifying the areas that are most vulnerable to fishing activities in conservation planning.
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McLaverty, C., GE Dinesen, H. Gislason, ME Brooks, and OR Eigaard. "Biological traits of benthic macrofauna show sizebased differences in response to bottom trawling intensity." Marine Ecology Progress Series 671 (August 5, 2021): 1–19. http://dx.doi.org/10.3354/meps13790.
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Bottom trawling results in widespread impacts to the structure and composition of benthic communities. Although an ecosystem approach to fisheries management aims to conserve marine biodiversity and ecosystem function, there remains a lack of empirical evidence regarding the effects of trawling on benthic functional properties. Here, we examined the sensitivity of benthic macrofauna communities to trawling using their biological traits, and compared trait responses across size-categories and survey types. We collected 84 benthic soft-sediment samples by Van Veen grab (0.1 m2) in the Kattegat in 2016, and complemented with 827 Haps cores (0.0143 m2) gathered over a long-term monitoring programme between 2006 and 2013. By analysing trait response in 3 size categories (small: 1-4 mm fraction; large: ≥4 mm fraction; full community: all individuals combined), we demonstrate a size-dependent effect of trawling on benthic trait composition, where the traits of large-bodied fauna (≥4 mm) were more sensitive. Specifically, larger sessile, deep-living, suspension-feeding, tube-dwelling, subsurface deposit-feeding, burrow-dwelling, and long-lived (≥10 yr) individuals were among the most affected. Our results based on large fauna were largely in agreement with trait responses observed in the multi-year monitoring data, suggesting that trait data gathered from a targeted one-time sampling event can convey information on both acute (short-term) and chronic (long-term) trawling impacts. Given that most trawling impact assessments do not consider size-based effects, we outline how size-separating the community can be used to improve the detectability of trawling impacts, and provide new insights into the functional impacts of fishing on the seabed.
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Jacobsen, Lif Lund. "State entrepreneurship in New South Wales’ trawl fishery, 1914-1923." International Journal of Maritime History 32, no. 3 (August 2020): 636–55. http://dx.doi.org/10.1177/0843871420949092.
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In 1914, the New South Wales (NSW) Government decided to alter its fisheries policy, with the development of an offshore trawling industry supplanting support for inshore fishing as its key development objective. Accordingly, between 1915 and 1923 the NSW Government operated a commercial trawling industry designed to fish previously unexploited fish stocks on the state’s continental shelf. The State Trawling Industry (STI) was designed to meet a mix of social and economic policy goals, with the NSW Government controlling all parts of the production line from catching to selling produce. This article examines the business structure of the enterprise to reveal the reasons for its economic failure. It argues that government entrepreneurship created a new consumer market and unintentionally paved the way for the rise of a modern private trawling industry.
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Stobutzki, Ilona, Peter Jones, and Margaret Miller. "A comparison of fish bycatch communities between areas open and closed to prawn trawling in an Australian tropical fishery." ICES Journal of Marine Science 60, no. 5 (January 1, 2003): 951–66. http://dx.doi.org/10.1016/s1054-3139(03)00117-6.
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Abstract The bycatch fish community was compared between areas open and closed to prawn trawling in Australia's Northern Prawn Fishery to investigate the impacts of the fishery. Two regions of a large (∼6648 km2) closure were compared, with three areas in each region, one closed to trawling (Closed) and two open to trawling, one near the closure (Near) and one farther from the closure (Far). Sampling was undertaken both day and night. The two regions and two times were analysed separately using both multivariate and univariate analyses to examine changes in overall community structure and differences in individual species. Overall the results were equivocal with respect to the impact of trawling. The multivariate and univariate analyses showed that in both regions, during both day and night, the bycatch fish community of the Far open area differed from the Near and Closed areas, while the latter were similar. This at least partly reflected differences in depth and sediment. For individual species, most showed no significant difference between the areas open and closed to trawling. Of the significant results there was no consistent tendency for species to be more likely to occur inside the closure or be at a higher density or larger size within the closure. Benthic and demersal species, those more susceptible to capture by prawn trawls, were not consistently less likely to occur or at a lower biomass in the open areas. The lack of a strong contrast in the fish community between the open and closed areas is probably due to the comparatively low effort in the fishery, the highly aggregated nature of the trawling and the fact the fishery does not target the bycatch species. These factors may reduce the potential impact of trawling on the fish bycatch.
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McConnaughey, Robert A., and Stephen E. Syrjala. "Short-term effects of bottom trawling and a storm event on soft-bottom benthos in the eastern Bering Sea." ICES Journal of Marine Science 71, no. 9 (April 16, 2014): 2469–83. http://dx.doi.org/10.1093/icesjms/fsu054.
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Abstract A Before–After Control–Impact (BACI) experiment was conducted to investigate the effects of a commercial bottom trawl on benthic invertebrates in a sandy and previously untrawled area of the eastern Bering Sea. Six pairs of experimental and control corridors were sampled with a research trawl before and after four consecutive tows with the commercial otter trawl. A major storm event occurred during the experiment, and it was possible to differentiate its effect from that of the trawling using the BACI model. Species composition changed very little; Asterias amurensis and Paralithodes camtschaticus comprised over 80% of the total invertebrate biomass (kg ha−1) during each year of the study. In general, the commercial trawl did not significantly affect the biomass of the benthic invertebrate populations. The trawling effect after 4–14 d was statistically significant in three of the 24 taxa that were analysed, which was, as expected, because of nothing more than random variation with α = 0.10. Biomass immediately after the trawling disturbance was lower for 15 of the taxa and higher for the other nine, with a median change of −14.2%. Similarly, the effect of trawling on invertebrate biomass after one year was not statistically significant for any of the taxonomic groups (p ≥ 0.23), indicating no evidence of a delayed response to the commercial-trawl disturbance. Further analysis suggests that storms have an overall greater effect on the benthos than do bottom trawls at this location. Both the numbers of taxa significantly affected by trawling and the storm (3 vs. 12), as well as the median sizes of these effects −14.2% vs. −22.0%), were greater for the storm event. Results from this study are combined with those from a related investigation of chronic trawling effects to propose an adaptive management strategy for the study region, including rotating area closures to mitigate for temporary trawling effects.
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Prantoni, Alessandro Lívio, Paulo da Cunha Lana, Leonardo Sandrini-Neto, Orlei Antônio Negrello Filho, and Verônica Maria de Oliveira. "An experimental evaluation of the short-term effects of trawling on infaunal assemblages of the coast off southern Brazil." Journal of the Marine Biological Association of the United Kingdom 93, no. 2 (April 3, 2012): 495–502. http://dx.doi.org/10.1017/s002531541200029x.
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Bottom trawling is a large-scale fishing activity along the Brazilian coast, but its effects on benthic infauna are still poorly known. This is the first experimental evaluation of benthic responses to bottom trawling along the Brazilian coast. We tested the effects of trawling on macroinfaunal assemblages on the inner continental shelf off Paraná (southern Brazil) by using a sampling design with adjacent trawl and control areas. We hypothesized that if trawl fishing has a negative effect then we should expect lower numbers of species and lower benthic densities after an experimental trawling. Sampling was conducted at adjacent sites within each area to minimize confounding due to spatial variation. Five sites were sampled at a control, and five at an experimental area for infaunal and sedimentological variables. Sampling was carried out just before and one hour after experimental trawling. Multidimensional scaling followed by a PERMANOVA did not show any clear variation tendencies in the structure of the benthic assemblages in the impacted area before and after trawling. However, variance analysis showed a significant and unexpected increase in infaunal total density, in the density of the numerically dominant species (except for the polychaetes Capitella sp. and Loandalia tricuspis) and in species richness in the experimental area. Conversely, no significant variations were recorded in the control area. We suggest that the overall increase in benthic density after a disturbance is correlated with the reworking of the sediment matrix and benefits the suspension-feeders after sediment resuspension.
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Chimienti, Giovanni, Lorenzo Angeletti, Lucia Rizzo, Angelo Tursi, and Francesco Mastrototaro. "ROVvstrawling approaches in the study of benthic communities: the case ofPennatula rubra(Cnidaria: Pennatulacea)." Journal of the Marine Biological Association of the United Kingdom 98, no. 8 (October 8, 2018): 1859–69. http://dx.doi.org/10.1017/s0025315418000851.
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Megabenthic soft bottom communities of trawlable grounds have been studied since the first few decades of the last century, thanks to trawl fishing technologies. Despite providing an extensive amount of presence data, trawling cannot be considered reliable from a quantitative point of view, frequently giving only weak information about sessile species density, large and small-scale distribution and main habitat features. The recent development of visual technologies on remotely operated vehicles (ROVs) can give a more accurate approach for the study of mega-epibenthic communities. The present study reports the application of both ROV imaging and trawling approaches for the study of a large aggregation (i.e. field) of the red sea penPennatula rubrain the Ionian Sea. Density, biomass and population structure were studied in the same population ofP. rubra. The density assessed by ROV was significantly higher than that estimated with a three-year series of trawling surveys. Trawling gear efficiency in the removal ofP. rubrawas low overall. Incidental mortality can be very high due to damage to those specimens that encounter the trawl net but are not directly captured. However, sampling of several colonies by trawling was necessary to establish biometric correlations to estimates of size and biomass from ROV imaging. Trawling catch abundance/biomass data could be useful to identify areas of higher concentration of sea pens, while ROV imaging can be used to monitor these fields in a non-destructive manner that would be consistent with protection measures.
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Johnson, Andrew Frederick, Giulia Gorelli, Stuart Rees Jenkins, Jan Geert Hiddink, and Hilmar Hinz. "Effects of bottom trawling on fish foraging and feeding." Proceedings of the Royal Society B: Biological Sciences 282, no. 1799 (January 22, 2015): 20142336. http://dx.doi.org/10.1098/rspb.2014.2336.
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The effects of bottom trawling on benthic invertebrates include reductions of biomass, diversity and body size. These changes may negatively affect prey availability for demersal fishes, potentially leading to reduced food intake, body condition and yield of fishes in chronically trawled areas. Here, the effect of trawling on the prey availability and diet of two commercially important flatfish species, plaice ( Pleuronectes platessa ) and dab ( Limanda limanda ), was investigated over a trawling intensity gradient in the Irish Sea. Previous work in this area has shown that trawling negatively affects the condition of plaice but not of dab. This study showed that reductions in local prey availability did not result in reduced feeding of fish. As trawling frequency increased, both fish and prey biomass declined, such that the ratio of fish to prey remained unchanged. Consequently, even at frequently trawled sites with low prey biomass, both plaice and dab maintained constant levels of stomach fullness and gut energy contents. However, dietary shifts in plaice towards energy-poor prey items were evident when prey species were analysed individually. This, together with a potential decrease in foraging efficiency due to low prey densities, was seen as the most plausible cause for the reduced body condition observed. Understanding the relationship between trawling, benthic impacts, fish foraging and resultant body condition is an important step in designing successful mitigation measures for future management strategies in bottom trawl fisheries.
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Moritz, C., D. Gravel, L. Savard, C. W. McKindsey, J. C. Brêthes, and P. Archambault. "No more detectable fishing effect on Northern Gulf of St Lawrence benthic invertebrates." ICES Journal of Marine Science 72, no. 8 (July 16, 2015): 2457–66. http://dx.doi.org/10.1093/icesjms/fsv124.
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Abstract Trawling has been reported worldwide to alter seabed structure, and thus benthic habitats and ecosystems. Usually, a decrease in species richness and biomass is observed, and community structure is modified towards more opportunistic species. The Gulf of St Lawrence (Canada) has been intensely exploited since the 17th century, including net, longline, dredge and trawl fishing activities. Recently, the collapse of groundfish stocks induced a shift in fishing practices toward shrimp trawling, which is currently considered a sustainable fishing activity in the region. However, no long-term study has evaluated the potential effects of trawling disturbances on benthic mega-invertebrates. We investigated whether shrimp trawling had long- (ca. 20 years), mid- (ca. 10 years), and short-term (ca. 4 years) impacts on benthic mega-invertebrate taxa richness, biomass, and community structure. Scientific and fishery trawling data analyses showed that no significant long-, mid-, or short-term effect was detected on taxa richness. Significant but weak effects on biomass and community structure were detected at the mesoscale, i.e. at the scale of fishing grounds. In this long-exploited ecosystem, we suggest that a critical level of disturbance was attained by the first gear passages, which occurred decades ago and had irreversible impacts on the seabed by removing vulnerable taxa and structures that provided three-dimensional habitats. It is likely that benthic communities have subsequently reached a disturbed state of equilibrium on which current trawling disturbance has limited or no further impacts.
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Clark, Malcolm. "Effects of Trawling on Seamounts." Oceanography 23, no. 01 (March 1, 2010): 132–33. http://dx.doi.org/10.5670/oceanog.2010.93.
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McCallum, E. "The fittest fish escape trawling." Journal of Experimental Biology 218, no. 21 (November 1, 2015): 3348–49. http://dx.doi.org/10.1242/jeb.112656.
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Gullapalli, Venkata Karthik, and Aishwarya Asesh. "Data Trawling and Security Strategies." IOSR Journal of Computer Engineering 16, no. 6 (2014): 57–59. http://dx.doi.org/10.9790/0661-16635759.
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Leonard, John W. "Cable behavior in bottom trawling." Ocean Engineering 12, no. 2 (January 1985): 117–30. http://dx.doi.org/10.1016/0029-8018(85)90076-9.
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Osipov, Evgeny, and Herman Pavlov. "PACIFIC FLYING SQUID TRAWLING TECHNOLOGY." Fisheries 2021, no. 3 (June 7, 2021): 108–11. http://dx.doi.org/10.37663/0131-6184-2021-3-108-111.
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In this work, research has been carried out on the technology of fishing for Pacific flying squid with trawls. The substantiation of the use of appropriate net webs with landing ratios to improve filtration in the trawl bag and in the winding part, ensuring the maximum catch and excluding damage, has been carried out.
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Laurenson, C. H., and I. G. Priede. "The diet and trophic ecology of anglerfish Lophius piscatorius at the Shetland Islands, UK." Journal of the Marine Biological Association of the United Kingdom 85, no. 2 (March 31, 2005): 419–24. http://dx.doi.org/10.1017/s0025315405011355h.
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The diet of anglerfish (Lophius piscatorius), based on the analysis of stomach contents, was investigated in the Shetland Islands. Samples were obtained during trawling for sandeel (Ammodytidae species) and demersal trawling when mainly whitefish (gadoids) are targeted. This allowed the diets of samples collected from different areas and at different times to be compared. The diets in different length groups were also compared and niche breadth investigated.A wide range of prey types, mainly fish, were recorded but the main prey was Norway pout (Trisopterus esmarkii) and lesser sandeel (Ammodytes marinus). Diet composition varied seasonally. In samples collected during whitefish trawling the occurrence of empty stomachs decreased from the first to the third quarters and generally increased with increasing anglerfish size. Empty stomachs occurred less frequently in samples collected from areas where sandeel fishing occurred compared to areas where whitefish trawling occurred.
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Eigaard, Ole R., Francois Bastardie, Niels T. Hintzen, Lene Buhl-Mortensen, Pål Buhl-Mortensen, Rui Catarino, Grete E. Dinesen, et al. "The footprint of bottom trawling in European waters: distribution, intensity, and seabed integrity." ICES Journal of Marine Science 74, no. 3 (December 6, 2016): 847–65. http://dx.doi.org/10.1093/icesjms/fsw194.
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Mapping trawling pressure on the benthic habitats is needed as background to support an ecosystem approach to fisheries management. The extent and intensity of bottom trawling on the European continental shelf (0–1000 m) was analysed from logbook statistics and vessel monitoring system data for 2010–2012 at a grid cell resolution of 1 × 1 min longitude and latitude. Trawling intensity profiles with seabed impact at the surface and subsurface level are presented for 14 management areas in the North-east Atlantic, Baltic Sea and Mediterranean Sea. The footprint of the management areas ranged between 53–99% and 6–94% for the depth zone from 0 to 200 m (Shallow) and from 201 to 1000 m (Deep), respectively. The footprint was estimated as the total area of all grid cells that were trawled fully or partially. Excluding the untrawled proportions reduced the footprint estimates to 28–85% and 2–77%. Largest footprints per unit landings were observed off Portugal and in the Mediterranean Sea. Mean trawling intensity ranged between 0.5 and 8.5 times per year, but was less in the Deep zone with a maximum intensity of 6.4. Highest intensities were recorded in the Skagerrak-Kattegat, Iberian Portuguese area, Tyrrhenian Sea and Adriatic Sea. Bottom trawling was highly aggregated. For the Shallow zone the seabed area where 90% of the effort occurred comprised between 17% and 63% (median 36%) of the management area. Footprints were high over a broad range of soft sediment habitats. Using the longevity distribution of the untrawled infaunal community, the seabed integrity was estimated as the proportion of the biomass of benthic taxa where the trawling interval at the subsurface level exceeds their life span. Seabed integrity was low (<0.1) in large parts of the European continental shelfs, although smaller pockets of seabed with higher integrity values occur. The methods developed here integrate official fishing effort statistics and industry-based gear information to provide high-resolution pressure maps and indicators, which greatly improve the basis for assessing and managing benthic pressure from bottom trawling. Further they provide quantitative estimates of trawling impact on a continuous scale by which managers can steer.
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Munga, Cosmas Nzaka, Edward Kimani, and Ann Vanreusel. "Ecological and socio-economic assessment of Kenyan coastal fisheries: the case of Malindi-Ungwana Bay artisanal fisheries versus semi-industrial bottom trawling." Afrika Focus 26, no. 2 (February 26, 2013): 151–64. http://dx.doi.org/10.1163/2031356x-02602010.
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This study explores and describes the status of the fisheries resources in the Malindi-Ungwana Bay, Kenya. In addition to shrimp bottom trawling, the bay also supports a variety of artisanal fishing techniques with associated resource-use conflict experienced for quite some time until a ban on bottom trawling was imposed. This study therefore, focuses on a before and after the trawling ban effect on shrimp populations and finfish bycatch distribution and abundance, and the characterisation of artisanal finfish catches in terms of catch composition, catch-per-unit-effort, and mean trophic level by vessel-gear categories. Apart from providing the current status of exploitation level of the fisheries resources, the scientific information generated from this study is also useful for the revision of the shrimp fishery management plan that was formulated with inadequate scientific and background information during the six year bottom trawling ban in the bay.
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Fleddum, A., L. J. Atkinson, J. G. Field, and P. Shin. "Changes in biological traits of macro-benthic communities subjected to different intensities of demersal trawling along the west coast of southern Africa." Journal of the Marine Biological Association of the United Kingdom 93, no. 8 (July 9, 2013): 2027–38. http://dx.doi.org/10.1017/s0025315413000647.
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Biological traits analysis (BTA) is considered to be a powerful technique for describing the ecological functioning of marine benthic assemblages. This study is the first to apply BTA to assess differences in the traits of benthic faunal assemblages between areas exposed to heavy and light trawling in a major upwelling ecosystem along the west coast of southern Africa. The data were collected from two sampling locations in Namibia and six sampling locations in South Africa. The intensity of trawling varied from area to area. Significant differences in biological traits (BT) were detected between heavily and lightly trawled areas. Weighted infaunal traits showed significant differences between heavily and lightly trawled areas for 17% of the traits investigated, while 24% of epifaunal traits investigated were significantly different between areas of different trawling intensities. This suggests that the measured BTs of the epifauna might be more sensitive to trawling disturbances than BTs of the infauna. The infaunal traits differed significantly between areas with larger or smaller proportions of sand and mud. Nevertheless, more of the significant differences in infaunal BTs were related to variations in trawling intensity than to variations in sediment composition. Significant modifications of BTs are likely to lead to modified functioning of the community and provide more general potential indicators for management than those based on species. The study confirms the need for more basic biological and life history data on macro-benthic invertebrates but nevertheless shows that BTA detected specific features that correlate with trawling intensity and that these features may be important for epifaunal assemblage functioning.
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Hiddink, J. G., S. Jennings, M. J. Kaiser, A. M. Queirós, D. E. Duplisea, and G. J. Piet. "Cumulative impacts of seabed trawl disturbance on benthic biomass, production, and species richness in different habitats." Canadian Journal of Fisheries and Aquatic Sciences 63, no. 4 (April 1, 2006): 721–36. http://dx.doi.org/10.1139/f05-266.
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Bottom trawling causes widespread disturbance of sediments in shelf seas and can have a negative impact on benthic fauna. We conducted a large-scale assessment of bottom trawl fishing of benthic fauna in different habitats, using a theoretical, size-based model that included habitat features. Species richness was estimated based on a generalized body mass versus species richness relationship. The model was validated by sampling 33 stations subject to a range of trawling intensities in four shallow, soft sediment areas in the North Sea. Both the model and the field data demonstrated that trawling reduced biomass, production, and species richness. The impacts of trawling were greatest in areas with low levels of natural disturbance, while the impact of trawling was small in areas with high rates of natural disturbance. For the North Sea, the model showed that the bottom trawl fleet reduced benthic biomass and production by 56% and 21%, respectively, compared with an unfished situation. Because of the many simplifications and assumptions required to synthesize these data, additional work is required to refine the model and evaluate applicability in other geographic areas. Our model enables managers to understand the consequences of altering the distribution of fishing activities on benthic production and hence on food web processes.
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Yesson, Chris, Jess Fisher, Taylor Gorham, Chris J. Turner, Nanette Hammeken Arboe, Martin E. Blicher, and Kirsty M. Kemp. "The impact of trawling on the epibenthic megafauna of the west Greenland shelf." ICES Journal of Marine Science 74, no. 3 (December 22, 2016): 866–76. http://dx.doi.org/10.1093/icesjms/fsw206.
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Benthic habitats are important elements of polar marine environments, but can be vulnerable to anthropogenic influences such as trawling. Bottom trawling can reduce diversity and alter communities, although some habitats show resilience. The shrimp trawl fishery of West Greenland is a significant part of Greenland's economy. It operates along the west coast from the narrow rockier shelf of the south, up to deeper, muddy areas around Disko Bay. Here we use a benthic drop camera to sample 201 sites between latitudes 60–72°N and depths of 61–725m. Linear models examined relationships of taxon abundance and diversity with bottom trawling intensity and environment (depth, temperature, current, iceberg concentration). Trawling intensity is the most important factor determining the overall abundance of benthic organisms, accounting for 12–16% of variance, although environmental conditions also show significant associations. Sessile erect organisms such as corals show a significant negative response to trawling. Soft sediment communities show a higher resilience than rocky areas. On soft sediments significantly lower abundance characterises sites trawled under five years ago. On hard/mixed ground reduced abundance remains characteristic of sites trawled a decade ago. Continued monitoring of benthic habitats is an essential part of evaluating the ongoing impacts of trawl fisheries.
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Dupaix, Amaël, Laurène Mérillet, Dorothée Kopp, Maud Mouchet, and Marianne Robert. "Using biological traits to get insights into the bentho-demersal community sensitivity to trawling in the Celtic Sea." ICES Journal of Marine Science 78, no. 3 (February 7, 2021): 1063–73. http://dx.doi.org/10.1093/icesjms/fsab011.
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Abstract Coastal marine ecosystems are under many pressures, including bottom trawling, which is the most widespread human activity that directly affects seabed habitats. Therefore, it is of great importance to characterize the impacts of bottom trawling on bentho-demersal communities, which can be done through the study of indicators sensitive to trawling pressure. Using a functional indicator applied to 54 underwater video transects, we mapped the sensitivity to trawling of epibenthic invertebrates and fish communities in the Celtic Sea. We determined the relative influence of environmental and fishing variables on sensitivity and traits distribution. Our results suggest that community sensitivity to trawling is mainly driven by a spatial gradient of depth and primary productivity that separates the area into two main regions: a shallow, productive area, with low sensitivity and a higher abundance of swimming and crawling organisms, and a deeper, less productive area, with higher sensitivity due to a higher abundance of fixed, filter-feeding organisms. Fishing intensity also drives the sensitivity of communities confirming that they have already been shaped by a long history of mixed fisheries. The methodology used here provides a valuable monitoring tool and could be used to predict communities’ response to changes in fishing intensity and climate change.
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Sañé, E., J. Martín, P. Puig, and A. Palanques. "Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea." Biogeosciences 10, no. 12 (December 11, 2013): 8093–108. http://dx.doi.org/10.5194/bg-10-8093-2013.
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Abstract. Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analysed in sediments from the flanks of the La Fonera (Palamós) submarine canyon (NW Mediterranean Sea), where a commercial bottom trawling fishery has been active for more than 70 yr. More specifically, we investigated how trawling-induced sediment reworking affects the quality of sedimentary organic matter which reaches the seafloor and accumulates in the sediment column, which is fundamental for the development of benthic communities. Sediment samples were collected during two oceanographic cruises in spring and autumn 2011. The sampled sites included trawl fishing grounds as well as pristine (control) areas. We report that bottom trawling in the flanks of the La Fonera Canyon has caused an alteration of the quality of the organic matter accumulated in the upper 5 cm of the seafloor. The use of a wide pool of biochemical tracers characterized by different reactivity to degradation allowed for us to discriminate the long-term effects of trawl-induced sediment reworking from the natural variability caused by the seasonal cycle of production and sinking of biogenic particles. Differences between untrawled and trawled areas were evidenced by labile amino acids, while differences between spring and autumn samples were detected only by the more labile indicators chlorophyll a and monounsaturated fatty acids. These results suggest that changes in the biochemical composition of the sedimentary organic matter caused by bottom trawling can be more relevant than those associated with natural seasonality and pose serious concerns about the ecological sustainability of deep-sea trawling activities.
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Sañé, E., J. Martín, P. Puig, and A. Palanques. "Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea." Biogeosciences Discussions 9, no. 12 (December 18, 2012): 18601–54. http://dx.doi.org/10.5194/bgd-9-18601-2012.
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Abstract. Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analyzed in sediments from the flanks of the La Fonera (Palamós) submarine canyon (NW Mediterranean Sea), where a commercial bottom trawling fishery has been active for more than 70 yr. More specifically, we investigated how trawling-induced sediment reworking affects the quality of sedimentary organic matter which reaches the seafloor and accumulates in the sediment column, which is fundamental for the development of benthic communities. Sediment samples were collected during two oceanographic cruises in spring and autumn 2011. The sampled sites included trawl fishing grounds as well as pristine (control) areas. We report that bottom trawling in the flanks of the La Fonera Canyon has caused an alteration of the quality of the organic matter accumulated in the upper 5 cm of the seafloor. The use of a wide pool of biochemical tracers characterized by different reactivity to degradation allowed us to discriminate the long-term effects of trawled-induced sediment reworking from the natural variability caused by the seasonal cycle of production and sinking of biogenic particles. Differences between untrawled and trawled areas were evidenced by labile amino acids, while differences between spring and autumn samples were detected only by the more labile indicators chlorophyll a and mono-unsaturated fatty acids. These results suggest that changes in the biochemical composition of the sedimentary organic matter caused by bottom trawling can be more relevant than those associated with natural seasonality and pose serious concerns about the ecological sustainability of deep-sea trawling activities.
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Couce, Elena, Michaela Schratzberger, and Georg H. Engelhard. "Reconstructing three decades of total international trawling effort in the North Sea." Earth System Science Data 12, no. 1 (February 17, 2020): 373–86. http://dx.doi.org/10.5194/essd-12-373-2020.
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Abstract. Fishing – especially trawling – is one of the most ubiquitous anthropogenic pressures on marine ecosystems worldwide, yet very few long-term, spatially explicit datasets on trawling effort exist; this greatly hampers our understanding of the medium- to long-term impact of trawling. This important gap is addressed here for the North Sea, a highly productive shelf sea which is also subject to many anthropogenic pressures. For a 31-year time span (1985–2015), we provide a gridded dataset of the spatial distribution of total international otter and beam trawling effort, with a resolution of 0.5∘ latitude by 1∘ longitude, over the North Sea. The dataset was largely reconstructed using compiled effort data from seven fishing effort time series, each covering shorter time spans and only some of the countries fishing the North Sea. For the years where effort data for particular countries were missing, the series was complemented using estimated (modelled) effort data. This new, long-term and large-scale trawling dataset may serve the wider scientific community, as well as those involved with policy and management, as a valuable information source on fishing pressure in a large marine ecosystem which is heavily impacted but which simultaneously provides a wealth of ecosystem services to society. The dataset is available on the Cefas Data Hub at: https://doi.org/10.14466/CefasDataHub.61, version 2 (Couce et al., 2019).
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Jennings, S., J. Lee, and J. G. Hiddink. "Assessing fishery footprints and the trade-offs between landings value, habitat sensitivity, and fishing impacts to inform marine spatial planning and an ecosystem approach." ICES Journal of Marine Science 69, no. 6 (April 6, 2012): 1053–63. http://dx.doi.org/10.1093/icesjms/fss050.
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Abstract Jennings, S., Lee, J., and Hiddink, J. G. 2012. Assessing fishery footprints and the trade-offs between landings value, habitat sensitivity, and fishing impacts to inform marine spatial planning and an ecosystem approach. – ICES Journal of Marine Science, 69: 1053–1063. European and national policy commitments require further integration of fisheries and environmental management. We measured fishery footprints and assessed trade-offs between landings value, habitat sensitivity, and beam trawling impacts in UK territorial waters in the southern and central North Sea where marine spatial planning is underway and a network of Marine Protected Areas has been proposed. For fleets (UK and non-UK) and years (2006–2010) considered, total trawled area included extensive ‘margins’ that always accounted for a smaller proportion of total fishing effort and value (proportions investigated were ≤10, 20, or 30%) than their proportional contribution to total habitat sensitivity and trawling impact. Interannual and fleet-related differences in the distribution and intensity of trawling activity, driven by location choice and fisheries regulations, had more influence on overall trawling impacts than the exclusion of beam trawlers from a proposed network of Marine Protected Areas. If reducing habitat impacts is adopted as an objective of fisheries or environmental management, then the direct management of fishing footprints, e.g. by defining fishing grounds that exclude existing margins, can disproportionately reduce trawling impacts per unit effort or value.
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Smith, C. J., A. C. Banks, and K.-N. Papadopoulou. "Improving the quantitative estimation of trawling impacts from sidescan-sonar and underwater-video imagery." ICES Journal of Marine Science 64, no. 9 (December 1, 2007): 1692–701. http://dx.doi.org/10.1093/icesjms/fsm165.
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Abstract Smith, C. J., Banks, A. C., and Papadopoulou, K.-N. 2007. Improving the quantitative estimation of trawling impacts from sidescan-sonar and underwater-video imagery. – ICES Journal of Marine Science, 64: 1692–1701. The techniques of sidescan sonar and towed, underwater-video sled were assessed as rapid-assessment methodologies for investigating trawl impacts on the substratum. Sidescan sonar is able to image a swathe of ∼200 m with a resolution of ∼20 cm at a speed of 2–3 knots, and marks of trawl doors could be observed. The towed video system imaged a swathe of 1–2 m with a resolution of 1–2 cm at a speed of ∼1 knot, and trawl-door marks, scrape marks, local bioturbation features, and fauna could be observed. Multiple tows using both methodologies were carried out in two areas in Heraklion Bay, Crete. One area, experimentally trawled, was 80–90 m deep and characterized by mixed, maerly sediments; the other was a commercial trawl lane ∼200 m deep characterized by silty-clay sediment. Descriptions of the types of trawling feature and impacts caused by trawling were made for both areas. Images were analysed from the commercial deeper trawling ground for area assessment. For sidescan-sonar records, direction of trawling and trawl-mark density by category were estimated at periodic intervals along the track. For video, categories for trawl-mark density and level of bioturbation were estimated, along with the density of the crinoid Leptometra phalangium. Using geo-referenced positioning for each data point, area maps were constructed for each of the parameters, and correlations were tested between the different datasets. The use of the assessment techniques (characteristics, data usage, mapping, complementarity) in relation to trawling-impact studies is discussed, as well as possibilities for the use of the resulting data for management.