Trawl disturbance on benthic communities: Chronic effects and experimental predictions

School of Ocean Sciences, University of Wales, Bangor, Menai Bridge, Anglesey LL59 5AB, United Kingdom.
Ecological Applications (Impact Factor: 4.09). 05/2009; 19(3):761-73. DOI: 10.1890/08-0351.1
Source: PubMed

ABSTRACT Bottom trawling has widespread impacts on benthic communities and habitats. While the direct impacts of trawl disturbances on benthic communities have been extensively studied, the consequences from long-term chronic disturbances are less well understood. The response of benthic macrofauna to chronic otter-trawl disturbance from a Nephrops norvegicus (Norway lobster) fishery was investigated along a gradient of fishing intensity over a muddy fishing ground in the northeastern Irish Sea. Chronic otter trawling had a significant, negative effect on benthic infauna abundance, biomass, and species richness. Benthic epifauna abundance and species richness also showed a significant, negative response, while no such effect was evident for epibenthic biomass. Furthermore, chronic trawl disturbance led to clear changes in community composition of benthic infauna and epifauna. The results presented indicate that otter-trawl impacts are cumulative and can lead to profound changes in benthic communities, which may have far-reaching implications for the integrity of marine food webs. Studies investigating the short-term effects of fishing manipulations previously concluded that otter trawling on muddy substrates had only modest effects on the benthic biota. Hence, the results presented by this study highlight that data from experimental studies can not be readily extrapolated to an ecosystem level and that subtle cumulative effects may only become apparent when fishing disturbances are examined over larger spatial and temporal scales. Furthermore, this study shows that data on chronic effects of bottom trawling on the benthos will be vital in informing the recently advocated move toward an ecosystem approach in fisheries management. As bottom-trawl fisheries are expanding into ever deeper muddy habitats, the results presented here are an important step toward understanding the global ecosystem effects of bottom trawling.

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Available from: Michel J Kaiser, Dec 23, 2013
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    • "The direct impacts on fauna through dislodgement or damage of individuals are the most obvious effects caused by fishing gear, but the range of biological changes extends well beyond these physical impacts and can significantly alter the community composition and foodweb architecture in the ecosystems subjected to fishing disturbance . On the shelf high levels of trawling results in changes to overall community composition through substantial habitat alterations, removal of non-target species, and through attraction of scavengers and predators to trawled areas (Tillin et al., 2006; Hinz et al., 2009). "
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    ABSTRACT: Deep-sea fisheries operate globally throughout the world's oceans, chiefly targeting stocks on the upper and mid-continental slope and offshore seamounts. Major commercial fisheries occur, or have occurred, for species such as orange roughy, oreos, cardinalfish, grenadiers and alfonsino. Few deep fisheries have, however, been sustainable, with most deep-sea stocks having undergone rapid and substantial declines. Fishing in the deep sea not only harvests target species but can also cause unintended environmental harm, mostly from operating heavy bottom trawls and, to a lesser extent, bottom longlines. Bottom trawling over hard seabed (common on seamounts) routinely removes most of the benthic fauna, resulting in declines in faunal biodiversity, cover and abundance. Functionally, these impacts translate into loss of biogenic habitat from potentially large areas. Recent studies on longline fisheries show that their impact is much less than from trawl gear, but can still be significant. Benthic taxa, especially the dominant mega-faunal components of deep-sea systems such as corals and sponges, can be highly vulnerable to fishing impacts. Some taxa have natural resilience due to their size, shape, and structure, and some can survive in natural refuges inaccessible to trawls. However, many deep-sea invertebrates are exceptionally long-lived and grow extremely slowly: these biological attributes mean that the recovery capacity of the benthos is highly limited and prolonged, predicted to take decades to centuries after fishing has ceased. The low tolerance and protracted recovery of many deep-sea benthic communities has implications for managing environmental performance of deep-sea fisheries, including that (i) expectations for recovery and restoration of impacted areas may be unrealistic in acceptable time frames, (ii) the high vulnerability of deep-sea fauna makes spatial management—that includes strong and consistent conservation closures—an important priority, and (iii) biodiversity conservation should be. balanced with options for open areas that support sustainable fisheries.
    • "It is well known that impacts of chronic trawl disturbance are cumulative and can cause significant decrease in biomass of epifaunal species such as sponges, corals, or echinoderms (Collie et al., 1997; Wassenberg et al., 2002; Burridge et al., 2003) and lead to profound changes in benthic assemblage composition (Kaiser et al., 2002; Hinz et al., 2009; Atkinson et al., 2011), although sometimes it is not possible to separate the effect of fishing from other environmental variables (Queirós et al., 2006; Atkinson et al., 2011). In the heavily fished North Sea, which has also been subjected to fishing activity for many centuries, benthic communities showed decreases in abundance of bivalves (Frid and Clark, 2000) and benthic diversity (Kaiser and Spencer, 1996; Jennings and Reynolds, 2000) over a 60-year period. "
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    ABSTRACT: The structure, composition and distribution of epibenthic invertebrate assemblages on the Tail of the Grand Bank of Newfoundland and Flemish Cap (northwest Atlantic) were sampled using depth-stratified trawls. Faunal analysis of 152 uniquely identified taxa produced hierarchical synoptic tables of species associations with diagnostic indicators based on species fidelity. Twelve spatially coherent epibenthic megafaunal assemblages were identified, each with relatively sharp faunal boundaries and unique species attributes. These assemblages were shown a posteriori through ANOSIM to have statistically different species compositions, and were nested within three major regional-scale faunal groups: (I) the continental shelf of the Tail of the Grand Bank, typified by the sea cucumber Cucumaria frondosa and the sand dollar Echinarachnius parma; (II) the upper slope of the Grand Bank and top of Flemish Cap, typified by the sponges Radiella hemisphaerica and Iophon piceum and the sea star Ceramaster granularis; and (III) the lower slope of the Grand Bank and Flemish Cap, typified by the sea urchin Phormosoma placenta, and the sea pens Anthoptilum grandiflorum and Funiculina quadrangularis. Comparisons with literature on benthic species associations from a half century ago suggest that the assemblages identified herein have persisted in the area at least for decades. Detrended correspondence analysis (DCA) identified a well-defined biological gradient along the first axis with very high species turn-over. Ten environmental variables (including Trawling Intensity) were significantly correlated with the ordinated data. At one extreme the continental shelf faunal group (I) was associated with shallow depth (mostly, less than 200 m), coarse sediments and cold and fresh water associated with the Labrador Current. At the other extreme the lower slope faunal group (III; stations below 500 to 600 m throughout the study area) was strongly associated with deep water, muddy sediments, and warmer and saltier water. Conditional tests under a step-wise model identified the percentage of mud as having the greatest explanatory power (40%) of the tested environmental variables. Trawling Intensity explained 11% of the variation in the full data set in marginal tests. Species richness in the deep water assemblages (Cluster III) was significantly and negatively correlated with fishing intensity. The species most directly associated with high trawling intensity in the DCA were the hard-shelled scavenging and predatory gastropods and a thick-shelled bivalve, consistent with expectations based on the trawling impact literature. Our study fills a critical knowledge gap in this important fishing area, and our novel regional-scale maps of the epibenthic assemblages will facilitate the development of ecosystem-based models linking benthic and pelagic systems and inform biodiversity conservation.
    Deep Sea Research Part I Oceanographic Research Papers 08/2015; DOI:10.1016/j.dsr.2015.08.006 · 2.57 Impact Factor
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    • "installation costs . One important devel - opment , however , would be the integration of position data with images . Vessel Monitoring Systems ( VMS ) are used widely in fisheries science . VMS data can be used to map fishing activity ( Gerritsen and Lordan , 2011 ; Jennings and Lee , 2012 ) and quantify fishing impacts ( Witt and Godley , 2007 ; Hinz et al . , 2009 ; Lambert et al . , 2012 ) . Positional data can also be combined with logbook data ( Deng et al . , 2005 ; Bastardie et al . , 2010 ) to examine catch per unit effort ( ICES , 2011 ; Murray et al . , 2011 ) and to estimate biomass indices ( Murray et al . , 2013 ) . Incorporating on - board cameras with VMS and logbooks would provide s"
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    ABSTRACT: For EU member states to meet the requirements of the Marine Strategy Framework Directive and the reformed Common Fisheries Policy, it will be necessary to improve data collection related to many fisheries that are at present subject to relatively little monitoring or scientific research. This study evaluated the use of on-board camera systems to collect data from Cancer pagurus and Homarus gammarus fisheries. We evaluated the reliability of the hardware and its ability to collect images of sufficient accuracy and precision compared with using on-board observers. Fishers and on-board observers passed animals removed from traps across a defined area. The relationship between the in situ and predicted measurements of carapace length of lobsters or carapace width (CW) of crabs was investigated. The mean difference between the predicted and real crab measurements was 20.853 mm with a standard error of 0.378 mm. Suggesting that the model tends to underestimate the real CW slightly. The mean difference between predicted and real data for lobsters was 0.085 mm with a standard error of 0.208 mm. Sex allocation for crabs based on video images was 100% accurate. All male lobsters were correctly assigned. For lobsters .86 mm in length, the correct female sex allocation was 100% accurate. For smaller lobsters, the accuracy of sex allocation decreased to a low of 51% in lobsters ,70 mm. Camera systems were found to be a suitable method for collecting data on the size and sex of crabs and lobsters. The error attributable to using video data rather than manual measurement was less than 3 mm, which is sufficient to detect growth increments in these species. The requirements to collect basic species data are increasing and the ability to do so without on-board observers will reduce the cost implications of these requirements. Future computer automation of image extraction and measurements will increase the application of video systems for data collection.
    ICES Journal of Marine Science 03/2015; DOI:10.1093/icesjms/fsv030 · 2.38 Impact Factor
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