Bottom trawl fishing footprints on the world’s continental shelves

Publication history: Accepted - 23 August 2018; Published online - 8 October 2018.Bottom trawlers land around 19 million tons of fish and invertebrates annually, almost one-quarter of wild marine landings. The extent of bottom trawling footprint (seabed area trawled at least once in a specified region and time period) is often contested but poorly described. We quantify footprints using high-resolution satellite vessel monitoring system (VMS) and logbook data on 24 continental shelves and slopes to 1,000-m depth over at least 2 years. Trawling footprint varied markedly among regions: from <10% of seabed area in Australian and New Zealand waters, the Aleutian Islands, East Bering Sea, South Chile, and Gulf of Alaska to >50% in some European seas. Overall, 14% of the 7.8 million-km2 study area was trawled, and 86% was not trawled. Trawling activity was aggregated; the most intensively trawled areas accounting for 90% of activity comprised 77% of footprint on average. Regional swept area ratio (SAR; ratio of total swept area trawled annually to total area of region, a metric of trawling intensity) and footprint area were related, providing an approach to estimate regional trawling footprints when highresolution spatial data are unavailable. If SAR was ≤0.1, as in 8 of 24 regions, therewas >95% probability that >90%of seabed was not trawled. If SAR was 7.9, equal to the highest SAR recorded, there was >95% probability that >70% of seabed was trawled. Footprints were smaller and SAR was ≤0.25 in regions where fishing rates consistently met international sustainability benchmarks for fish stocks, implying collateral environmental benefits from sustainable fishing.Funding for meetings of the study group and salary support for R.O.A. were provided by the following: David and Lucile Packard Foundation; the Walton Family Foundation; the Alaska Seafood Cooperative; American Seafoods Group US; Blumar Seafoods Denmark; Clearwater Seafoods Inc.; Espersen Group; Glacier Fish Company LLC US; Gortons Seafood; Independent Fisheries Limited N.Z.; Nippon Suisan (USA), Inc.; Pesca Chile S.A.; Pacific Andes International Holdings, Ltd.; San Arawa, S.A.; Sanford Ltd. N.Z.; Sealord Group Ltd. N.Z.; South African Trawling Association; Trident Seafoods; and the Food and Agriculture Organisation of the United Nations. Additional funding to individual authors was provided by European Union Project BENTHIS EU-FP7 312088 (to A.D.R., O.R.E., F.B., N.T.H., L.B.-M., R.C., H.O.F., H.G., J.G.H., P.J., S.K., M.L., G.G.-M., N.P., P.E.P., T.R., A.S., B.V., and M.J.K.); the Instituto Português do Mar e da Atmosfera, Portugal (C.S.); the International Council for the Exploration of the Sea Science Fund (R.O.A. and K.M.H.); the Commonwealth Scientific and Industrial Research Organisation (C.R.P. and T.M.); the National Oceanic and Atmospheric Administration (R.A.M.); New Zealand Ministry for Primary Industries Projects BEN2012/01 and DAE2010/ 04D (to S.J.B. and R.F.); the Institute for Marine and Antarctic Studies, University of Tasmania and the Department of Primary Industries, Parks, Water and Environment, Tasmania, Australia (J.M.S.); and UK Department of Environment, Food and Rural Affairs Project MF1225 (to S.J.)

Magnetostratigraphy and biostratigraphy of the Upper Triassic and lowermost Jurassic succession, St. Audrie's Bay, U.K.

The St. Audrie's Bay section in west Somerset comprises the uppermost Mercia Mudstone Group, the Penarth Group and the basal Lias Group and includes a candidate Global Stratotype Section and Point for the base of the Jurassic. The magnetostratigraphy has been evaluated through 122 m of this section at 147 stratigraphic levels, which range in age from mid-Norian to earliest Hettangian. In red dolomitic mudstones, the remanence is carried predominantly by haematite, whereas in non-red lithologies, it is mostly carried by magnetite. The mean virtual geomagnetic poles fall near the mean Upper Triassic and Lower Jurassic apparent polar wander track and display the start of the northeast-directed track typical of the Jurassic. The magnetostratigraphy comprises nine major magnetozones, five of normal polarity and four reversed, together with several minor magnetozones. In the Mercia Mudstone Group, the 68 m of the Twyning Mudstone Formation examined includes three major normal magnetozones (SA2n, SA3n and SA4n) and the Blue Anchor Formation has predominantly reversed polarity (SA4r) except at its top, in the Williton Member. The Penarth Group and basal Lias Group have predominantly normal polarity (SA5 to SA6n) but short reversals occur within the Westbury Formation and at the base of the Lilstock Formation and the Lias Group (SA5r). This magnetostratigraphy is a good match with that found in the upper part of the Newark Supergroup succession in the eastern USA. The distinctive long reversal (SA4r) in the Blue Anchor Formation is equivalent to Newark Supergroup magnetozone interval E18r to E20r. Magnetozone SA5n, located mainly in the Penarth Group, probably equates with part of E22n and all of E23n in the Newark Supergroup. The reversed magnetozone, SA5r, at the base of the Lias Group, may correspond either with E23r in the Exeter Member (Passaic Formation) in the Newark Supergroup or with an undetected reverse polarity interval within the Newark Basin flood basalts. A change in the composition and diversity of terrestrial microfloras that occurs in the upper part of the Penarth Group at St. Audrie's Bay and elsewhere in the UK, is similar to that interpreted as marking the Triassic–Jurassic boundary in the Newark Supergroup. At St. Audrie's Bay, this change occurs c. 0.6 m below SA5r, within the Rhaetian, whereas in the Newark Supergroup, it occurs c. 20 m above the potentially equivalent E23r. Reconciliation of these disparities requires that either the microfloral changes are not synchronous between these locations or the change in the Newark Supergroup is time-equivalent with late Rhaetian conodont bearing strata. The correlation of marine and nonmarine Upper Triassic magnetostratigraphies is revaluated with the new data from St. Audrie's Bay, indicating the Twyning Mudstone and Blue Anchor formations are mid to late Alaunian (mid-Norian) in age. The Sevatian (late Norian) is represented by the Williton Member and the lower part of the Westbury Formation, but is incomplete because of disconformities at the base of the Williton Member and Penarth Group

Using vessel monitoring system (VMS) data to assess the impact of marine protection boundaries on blue ling fishing northwest of the British Isles

In 2009, the European Commission set restricted fishing areas northwest of the British Isles to protect deep-sea vulnerable marine ecosystems and fish stocks. Two protection areas which, historically, have been targeted by fisheries directed at blue ling (Molva dypterygia), were defined. The study aims to assess the effectiveness of restricting fishing activity within the protection areas during the blue ling spawning period (March–May) and to determine whether the existing boundaries are fit for purpose. Estimations of the spatial apportionment of blue ling landings within and outside the protection areas are achieved by combining low-resolution data from fishing vessel logbook entries with higher-resolution vessel monitoring system (VMS) data. High-resolution spatial apportionment of blue ling landings is limited by a lack of high-resolution logbook data, and certain assumptions need to be made on whether vessels are engaging in fishing activity at any individual VMS data point, based on vessel speed and types of fishing gear available. Although current measures appear to have influenced fishing activity in the vicinity of the protection areas, more evidence is needed for a robust evaluation of their effectiveness in protecting blue ling. Recommendations are made for improvements in data collection methods and data availability for research in support of monitoring, assessment and delineation of marine protection boundaries

Evaluating differences in marine spatial data resolution and robustness:A North Sea case study

Seabed substrates have the capacity to support a variety of marine communities. However, habitats provided by natural substrates are increasingly modified and supplemented by man-made structures. These provide hard surfaces suitable for colonisation by sedentary and/or non-migratory organisms, and may contribute to an interconnected system of benefit to diverse marine populations. Robust assessment of the influence of such structures is, therefore, a necessary consideration for their long-term management. The challenge of compiling and manipulating data for input to two North Sea models is described. Source data were processed and gridded at three different spatial resolutions to investigate the effect of scale on spatial relationships. Choice of grid size was found to exacerbate existing uncertainty in location and extent of features, influencing interpretation of their spatial distributions at the different scales examined. The small spatial footprint of man-made structures, compared with natural substrates, may lead to underestimation of the influence of the former at coarser model scales. Choices must be made between data availability, spatial resolution and accuracy, modelling and analysis requirements, to identify robust approaches to reliable outcomes. Model sensitivity and uncertainty analyses are recommended for application in data-limited situations. Greater openness and cooperation in data-sharing is required for robust scientific modelling to underpin decision-making in the marine environment

The footprint of bottom trawling in european waters: distribution, intensity, and seabed integrity

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 x 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 (&amp;lt; 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

Can aspects of the discharge regime associated with juvenile Atlantic salmon ( Salmo salar

Understanding salmonid discharge requirements can help inform management to conserve wild populations in a changing climate. This study developed Bayesian hierarchical mixed-effects models relating 0+ Atlantic salmon (Salmo salar L.) and trout (Salmo trutta L.) densities to different aspects of river discharge. Associations between these densities and nine hydrological variables representing the magnitude, frequency and duration of discharge events were evaluated using historical monitoring data from 36 sites on five rivers in England and Wales. All hydrological variables had weak associations with 0+ salmonid densities. More frequent high discharges between spawning and emergence were positively and negatively associated with 0+ salmon and trout densities, respectively. High discharges might increase spawning site availability for salmon and decrease egg-to-fry survival for trout. However, overall, only equivocal evidence was found regarding which discharge aspects affect juvenile salmonid densities. Therefore, a strategic review of juvenile salmonid monitoring programmes integrating environmental data collection is recommended

Benthic impact of fisheries in European waters: the distribution and intensity of bottom trawling

Mapping and monitoring of pressure from fishery on the marine benthic environment is necessary to support an ecosystem approach to fisheries management (EAFM). In many cases this need is not reflected in official fisheries statistics and logbooks, where focus typically is on catch rather than effort. Consequently, most logbook information is not well suited for quantitative estimation of seafloor impact (swept area and impact severity) of the different gears and trips. We developed a method to overcome this information deficiency of official statistics and produced European wide high-resolution fishing intensity maps (total yearly swept area within grid cells of 1*1 minutes longitude and latitude) for 2010, 2011 and 2012. The annual distribution and intensity of bottom trawling on the European continental shelf was analyzed for different management areas and gear groups, distinguishing between surface and sub-surface effects. Fishing pressure indicators were calculated and compared for each management area; i) proportion of area untrawled, ii) proportion of area with an annual swept area intensity ≥ 1, and iii) proportion of area where 90% of the effort is concentrated). The management area with the largest proportion of surface area being trawled ≥ 1 time a year was the Adriatic Sea (64%) and the management area with the lowest proportion of surface area being trawled ≥ 1 time a year was the Northwestern Shelf (15%). Also the Tyrrhenian Sea (45%), the Channel (41%) and the North Sea (36%) have a substantial part the seabed trawled at intensities above 1, indicating a high level of fishing pressure on the benthic habitats. The results of the analysis also showed that in all European seas, between 33% and 72% of the sea bed down to 200 m was not trawled during the study period. When considering all three fishing pressure indicators jointly (proportion of area untrawled, proportion with an annual intensity ≥ 1, and with 90% of the effort) four management areas draw attention; the North Sea, the Channel, the Tyrrhenian Sea and Adriatic Sea. These four areas all score relatively high on all three pressure indicators, and also have a substantial part (> 50%) of the total area impacted at the sub-surface level. Within the soft sediment habitats that dominate the continental shelf areas of Europe, mud habitats appear to be trawled most intensively while at the same time they likely have a higher sensitivity to bottom trawling as compared to the sandy and coarser sediments. Consequently, current fishing practices in parts of these four management areas could potentially compromise seafloor integrity

How do river nitrate concentrations respond to changes in land-use? A modelling case-study of headwaters in the River Derwent catchment, North Yorkshire, UK

A combined semi-distributed hydrological model (CASCADE/QUESTOR) is used to evaluate the steady-state that may be achieved after changes in land-use or management and to explore what additional factors need to be considered in representing catchment processes. Two rural headwater catchments of the River Derwent (North Yorkshire, UK) were studied where significant change in land-use occurred in the 1990s and the early 2000s. Much larger increases in mean nitrate concentration (55%) were observed in the catchment with significant groundwater influence (Pickering Beck) compared with the surface water-dominated catchment (13% increase). The increases in Pickering Beck were considerably greater than could be explained by the model in terms of land-use change. Consequently, the study serves to focus attention on the long-term increases in nitrate concentration reported in major UK aquifers and the ongoing and chronic impact this trend is likely to be having on surface water concentrations. For river environments, where groundwater is a source, such trends will mask the impact of measures proposed to reduce the risk of nitrate leaching from agricultural land. Model estimates of within-channel losses account for 15–40% of nitrate entering rivers