International Council for the Exploration of the Sea ICES CM 2004/Y:05 Annual Science Conference 22-25 September 2004 Vigo, Spain Developing the use of satellite fishing Vessel Monitoring System data in spatial management. C Mills, S. I. Rogers, M.L. Tasker, P.D. Eastwood and G.J. Piet. Abstract Fishing effort data, derived from Vessel Monitoring System (VMS) data and overflight observations, were used to quantify the relative intensity of demersal trawling on different seabed habitats in UK parts of the Irish Sea, based on 100% coverage vector maps of coastal and offshore marine landscapes. VMS data are used throughout European waters to track the location of fishing vessels >24m in length using GPS, and contribute to the monitoring, control and surveillance of fisheries. This paper describes the processing methods of VMS data used to identify the locations where fishing activity (rather than steaming) occurs, and to calculate fishing effort distributions using kernel density estimation in Geographic Information Systems (GIS). Complimentary data obtained from the observations of fishery protection aircraft were used to infer the distribution of the inshore fleets. Results suggest that vessel activity in the Irish Sea by >24m trawlers is most intense on extensive coarse sediment plains and in deep-water mud basins, and that some smaller features, particularly mud basins, sea mounds and gravel banks, are fished intensively by smaller vessels. The implications of these results for the selection and protection of habitats and species of nature conservation interest are discussed. Keywords: habitat protection, VMS, MPA, marine landscape, marine habitat, C. Mills, S Rogers, P Eastwood, Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk, NR33 0HT. [tel:+44 1502 562244 fax:+44 1502 524546. Email:s.i.rogers@cefas.co.uk.]. M Tasker, JNCC, Dunnet House, 7 Thistle Place, Aberdeen, Scotland, AB10 1UZ. [tel: +44 1224 655701 fax: +44 1224 621488. Email:mark.tasker@jncc.gov.uk]. G Piet, RIVO, PO Box 68, 1970 AB Ijmuiden, Netherlands [tel: + 31 255 564 660 fax: 31 255 564644. Email: G.J.Piet@rivo.wag-ur.nl]

Introduction The UK has recently completed a Review of Marine Nature Conservation as part of a wider strategy for sustainable development in the marine environment (Defra, 2004). A key element of the Review was a trial in a UK regional sea ‘The Irish Sea Pilot’ to test the balance of nature conservation needs with those of other human activities, and to show how far conservation management within the region could be delivered through existing legislation (Vincent et al., 2004). Important conclusions at this regional sea scale were that conservation requirements of broad marine landscapes, habitats and species could be partly addressed by spatial planning and zoning of human activities. Progress with nature conservation legislation and the enforcement of management action will, however, depend on the coordinated collection and interpretation of high-resolution datasets to support this approach. Comparisons between a number of sectors have shown that the adverse impacts of fishing activity rank highly relative to others (OSPAR, 2000), and that these impacts result in direct and indirect effects on species and communities (Jennings & Kaiser, 1998). The increased adoption in Europe of an ecosystem-based approach to Fisheries Management (FAO, 2002) has shown wider implications for the ecosystem in, for example, the interaction between the North Sea sandeel fishery and seabirds, and the damaging effects of trawling on cold-water coral reefs (OSPAR, 2003). However, the interaction between fishing activity and other threatened species and habitats is not fully understood, and not supported by comprehensive mapping of the seabed and the accurate routine surveillance of fishing vessels. A key outcome of the UK Review was the production of digital maps of Irish Sea marine landscapes, using geophysical and hydrographical datasets in lieu of biological information to classify habitats at the medium scale (Roff & Taylor, 2000; Vincent et al., 2004). Criteria used to separate landscapes into distinct types were depth, substratum type, current strength (sea bed stress), and topography (slope). The UK routinely collects data on the distribution of fishing vessels using direct observations from enforcement vessels and aircraft, and from vessel monitoring satellite data (VMS). From 1 January 2000, all EC fishing vessels over 24m were required to report their location, via satellite, to monitoring centres in their flag states, at 2-h intervals. The only exception is made for vessels that undertake trips of <24 h or fish exclusively within territorial waters (EU, 2002). The application of satellite Vessel Monitoring System (VMS) data to an increasing proportion of the EU fishing fleet suggests that this now has great potential not only for enforcing spatial closures, but also for monitoring the distribution of fishing effort in relation to different seabed features and habitats. VMS ‘black box’ recorders emit regular signals at two-hourly intervals which transmit position, speed, bearing and vessel registration number. The signal is first received by satellites and then by national receiving stations on the ground. Recent use of such data has been limited ((Dinmore et al., 2003; Rijnsdorp et al., 1998), and has highlighted the need to separate information on trawling activity from that of steaming between fishing locations. It is a more sophisticated version of current methods that use fishery protection aircraft to observe and record the position and activity of national and international fishing vessels in UK territorial waters (Rogers, Ellis & Dann, 2001).

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This paper shows how high-resolution bottom trawl fishing fleet activity in the Irish Sea (UK) is distributed in relation to different marine landscapes. This comparison will provide a more detailed picture than has previously been possible of those habitats that experience the greatest fishing pressure, and also will identify habitats that are trawled least. This is an important step in progressing the nature conservation objectives at the level of a regional sea. Materials and Methods Data describing the distribution of fishing effort was obtained from VMS data and the records of fishery protection overflight aircraft. These data were spatialised within the GIS package ESRI ArcGIS version 8.

Analysing the VMS data Since 2001 the UK VMS database, held at ITD Guildford, UK and maintained by the UK Fisheries Department has recorded the geographical position, speed, bearing and identification number of European vessels over 24m in length within UK waters. In this study, VMS data were used from 2003 for all UK and non-UK vessels in the Irish Sea (ICES Division 7a), to provide a detailed description of the distribution of fishing effort from the national and international over 24m fleet. Although the VMS database collects information for vessels using all gear types, this analysis has only considered those gears that directly impact the seabed, i.e. beam trawlers, dredgers and otter trawlers (Table 1). Table 1. Proportion of VMS signals by gear type received from the Irish Sea during 2003 for all nationalities. Those used in the analysis are shown in bold font.

Gear Type %

Otter Trawler (unspecified) 63.75Beam Trawl 27.07Dredging 3.17Other Pots or Mixed 1.69Danish or Scottish Fly Seine 1.38Midwater Demersal Trawl 1.16Long Lines 0.77Midwater Pair Trawl 0.48Gill Net (unspecified) 0.37Purse Seine 0.07Single Boat Midwater Trawl 0.04Gill Net 0.03Tangle Net 0.02Side Trawler (Pelagic/Demersal) 0.01

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Approximately 98% of the vessels operating in the Irish Sea were British, French, Belgian and Irish (Table 2), and these were used in all subsequent analyses. A small proportion of the gear type descriptors were missing from UK vessels, and on those occasions other national fisheries databases containing vessel registration and type were used to fill the gaps. A larger proportion (75%) of the non-UK vessel VMS returns were not attributed with gear type information. As detailed gear type databases for these international fleets were unavailable, a different approach was adopted. The gear types used by French, Belgian and Irish vessels were inferred by examining the location of the fleets by nation of origin, and applying expert knowledge of the local patterns of fisheries exploitation from throughout the Irish Sea. Using this method it was concluded that the Belgian fleet in the Irish Sea consisted almost entirely of beam trawlers while the French vessels were mainly otter trawlers. The Irish fleet, however, consisted of both beam trawlers and otter trawlers (M Armstrong, pers. comm.). Due to the known spatial distribution of the Irish fleets, which broadly separated the trawlers in the eastern Irish Sea from those exploiting the Nephrops fishery by otter trawlers in deeper muddy grounds, it was possible to distinguish the few remaining unclassified Irish vessels. The VMS database does not differentiate between those vessels that are stationery, fishing, or steaming. To make this distinction, transmitted vessel speeds of UK vessels were used. First, VMS satellite records for UK vessels were retained if they occurred within an ICES rectangle in which that vessel was known to have been fishing, based on logbook records. The frequency distribution of vessel speeds for these selected records was then used to determine thresholds for fishing speeds of each of the three gear categories. The frequency distribution for beam trawlers suggested that fishing was likely to occur took place at speeds of between 2-8 knots inclusive. Data for dredgers and otter trawlers suggested that fishing occurred at speeds between 1-4 knots inclusive. Table 2. Proportion of VMS signals by country received from the UK waters of the Irish Sea during 2003 for all vessels undertaking beam or otter trawling, and dredgers.

Country Percentage United Kingdom 34.72 France 23.75 Belgium 20.81 Ireland 17.89 Spain 1.45 Unknown 0.58 Norway 0.29 Denmark 0.15 Faeroes 0.13 Germany 0.11 Netherlands 0.09 Portugal 0.03

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In order to calculate the spatial distribution of fishing activity by each of the gear types, the VMS database was incorporated into a GIS. To estimate vessel density, we used a kernel density estimation (KDE) technique within ArcView Spatial Analyst. A 1 km grid was created covering the entire Irish Sea, and vessel positions were allocated to a search radius surrounding each cell. We used a radius of 14 km based on the least squares cross-validation technique (Silverman, 1986) that produced a surface that described local variation in fishing intensity with minimal over-smoothing. The vessel density per 1 km2 cell was calculated from the total number of records and the area of the search, with each vessel position weighted using an adapted Gaussian distribution so that recorded vessel positions close to the cells had a greater weighting.

Analysing the overflight data British Fishery Protection flights regularly survey UK territorial waters, flying routes over each quarter of an ICES rectangle approximately once a week during daylight hours throughout the year, and recording aerial observations of all vessels for enforcement purposes. Information on vessel activity (fishing or steaming), type of gear used, and the date, time and latitude and longitude of the observation are recorded. Data from aerial observations were most comprehensive for waters beyond 6 nm from shore. Observations of all otter trawlers, beam trawls and dredgers in the Irish Sea for the period 1993-2002 were standardised to take account of the variable number of over-flights, as not all sub-rectangles were visited on the same number of occasions per month. Each vessel observed was given a nominal score of 1, and this was then divided by the number of over-flights that had taken place in the relevant month and sub-rectangle. The resulting index, usually a fraction, expressed each observation in terms of the effort required to make it (Rogers et al., 2001). The total fishing effort in 1 km grids for the 10-year period was calculated using the KDE technique as described above.

Fishing effort in relation to Irish Sea marine landscapes The distribution of fishing effort, measured both by overflight data and VMS, in relation to the different marine landscapes in the Irish Sea was summarised by comparing the density surface outputs with the marine landscape map beyond 6 nm from shore (Vincent et al., 2004). The total number of fishing observations (using both VMS location records, and overflight observations) coinciding with each marine landscape, and the mean and standard deviation of the records per 1km2, was calculated for each marine landscape. The landscape ‘photic reef’ was omitted as this occurred only in inter-tidal and shallow sub-tidal waters.

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Results

Distribution of fishing effort by marine landscape The extent of 12 seabed marine landscapes shows that, in the UK part of the Irish Sea (Figure 2a), extensive areas of sediment plain characterise much of the Irish Sea (Table 3). Table 3. Characteristics of seabed marine landscapes in the Irish Sea (Vincent et al., 2004). Landscape Area

(km²) % of total

area Depth Substratum Water current

velocity Low bed-stress coarse sediment plains

13590 30.32 Variable Cobble, pebble, muddy gravel

Low

Fine sediment plains

10784 24.06 Variable Sand and muddy sand

Low

High bed-stress coarse sediment plains

8728 19.47 Variable Boulder, cobble, pebble and gravel

High

Deep-water mud basins

4039 9.01 > 50 m mud Very low

Sediment wave / megaripple field

2497 5.57 Variable Sand Moderate / High

Coastal sediment 2774 6.19 Intertidal to 50 m Mud, sand and gravel

Variable

Reefs (rocky / biogenic)

974 2.17 < 20 m Rock / biogenic Variable

Shallow-water mud basins

814 1.82 < 50 m mud Very low

Deep-water channel

250 0.56 > 150 m Cobble, gravel mixed sediment

Variable

Photic reefs 221 0.49 < 15m Bedrock, boulders, cobbles

Variable

Sand/ gravel banks 72 0.16 Variable Sand and gravel High Irish Sea mounds 74 0.17 > 20 m above

surrounding seabed

Rock with sediment veneer

Variable

The distribution of otter trawlers, beam trawls and dredgers greater than 24m in length during 2003 (Figure 2b), showed that effort was focussed in relatively deep water west of Wales and south-west of the Isle of Man, and in the eastern Irish Sea. The distribution of fishing activity using overflight data, which also records representative vessels greater than 24m length and so is more representative of all parts of the Irish Sea fishery, confirmed these patterns. These data showed that particularly high levels of effort by smaller (<24m) vessels were evident in deep water muddy areas between the Isle of Man and Northern Ireland. Analysis of the known activity of UK and international fleets in the Irish Sea suggested that Belgian beam trawlers were most active in the eastern Irish Sea and the deeper parts of St. Georges’ Channel in areas occupied by Irish vessels.

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The greatest number of VMS location records, and hence the highest level of fishing effort, occurred in areas of the Irish Sea consisting of low bed-stress coarse sediment plains (Figure 3a). Lower levels of fishing effort also occurred in sediment plains that experienced high bed-stress and in mega-ripple field areas (Figure 3a). These marine landscapes occupied extensive areas of the Irish Sea (Table 3), and presentation in terms of mean effort per unit landscape area (Figure 3b), confirmed that these landscapes were the focus of demersal trawling effort for the > 24 m fleet. Analysis of a larger component of the fishing fleet using overflight observations confirmed that high levels of effort were present on sediment plains, but also identified substantial numbers of vessel observations in areas of deep-water mud basins (Figure 4a). Although these mud basins are less extensive in the Irish Sea than areas of coarse and fine sediment (Table 3), they support the highest levels of effort per unit landscape area (Figure 4b). High levels of fishing activity were also identified in association with Irish Sea mounds, even though they are small seabed features with limited area of approximately 74 km2 (Table 3). Discussion This paper has confirmed that VMS satellite location records are a valuable tool in the spatial interpretation of fishing activities. Their use overcomes difficulties of direct human observation, either using vessels or by air, because records are comprehensive for all fishing vessels over 24m in length. Until the use of such systems is extended to the smaller parts of the fleet, it will still be necessary to make use of other methods of describing the distribution of smaller coastal vessels. Future developments in the analysis of fishing activity datasets could include a direct comparison between the two methods of data collection to infer the distribution of the smaller fishing vessels, perhaps using a mixed fleet such as demersal otter trawlers. Unlike other uses of these data for fisheries enforcement (Davis, 2001; Sabourenkov & Miller, 2002), we have illustrated their application to support the ecosystem objectives of fisheries management by identifying areas of high activity that correspond with different seabed features and habitats. In subsequent phases of this approach it will be necessary to interpret the consequences of this activity on the marine ecosystem, and if these are considered unsustainable, to propose appropriate remedial action. In the example chosen for this analysis, it was evident that the majority of demersal trawling activity by the >24m fleet occurred on homogeneous and extensive coarse sediments. This is likely to be a direct response to the presence of target species (mainly scallop and flatfish), which occur in greatest density in these habitats. In contrast, a more complete assessment of the distribution of all vessel sizes using overflight observations, showed that coastal trawlers, especially those exploiting Nephrops, occurred in greatest numbers per unit area in specific habitats (mud basins, sand banks, sea mounds) and where target fish and shellfish resources could be found. Despite these emerging associations between fleets and particular marine landscapes, it is important to interpret vessel density in terms of impact on the benthic fauna and flora. This is an important requirement if spatial restrictions on fishing activity are to

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be imposed as one measure to mitigate perceived adverse effects on marine habitats. Recent research has identified that the effects of trawling are often greater in environments where natural disturbance (e.g. caused by wave action or tides) is lower (Collie, Escanero & Valentine, 1997; Jennings et al., 1998). Thus shallow areas or those scoured by strong tides will be less impacted by a given level of trawling disturbance than deeper areas. Furthermore, trawling effort is patchy and so some areas are trawled very frequently, while other areas are trawled infrequently or not at all. Within any marine landscape, therefore, the consequences of fishing activity may not be directly related to the magnitude of fishing effort, and need to be resolved locally. Acknowledgements Thanks to Neil Golding and colleagues at the Joint Nature Conservation Committee for providing access to the landscape maps. This work was funded by Defra project AE1148 and MF0731. References

Collie, J.S., Escanero, G.A., & Valentine, P.C. (1997) Effects of bottom fishing on the benthic megafauna of Georges Bank. Marine Ecology Progress Series, 155, 159-172.

Davis, J. (2001). Monitoring control surveillance and vessel monitoring system requirements to combat IUU fishing. Expert Consult. on Illegal, Unreported and Unregulated Fishing, Sydney (Australia).

Defra (2004). Review of marine Nature Conservation: Working Group report to Government. Department for Environment, Food and Rural Affairs, London.

Dinmore, T., Duplisea, D., Maxwell, D., & Jennings, S. (2003) Impact of a large-scale area closure on patterns of fishing disturbance and the consequences for benthic communities. ICES Journal of Marine Science, 60, 371–380.

EU (2002). Communication from the Commission on the reform of the Common Fisheries Policy: Roadmap, Rep. No. ISBN 92-894-3077-X. Office for Official Publications of the European Communities, Luxembourg.

FAO (2002). Fisheries Management - 2. The Ecosystem Approach to Fisheries, Rep. No. ISSN 1020-5292. FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, Rome,.

Jennings, S. & Kaiser, M.J. (1998) The effects of fishing on Marine Ecosystems. Advances in Marine Biology, 34, 201-352.

OSPAR (2000). Quality Status Report 2000: Region II Greater North Sea, London.

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OSPAR (2003) Declaration of the Joint Ministerial Meeting of the Helsinki and OSPAR Commissions. JMM, 2003/3(final version)-E, 7.

Rijnsdorp, A.D., Buys, A.M., Storebeck, F., & Visser, E.G. (1998) Micro-scale distribution of beam trawl effort in the southern North Sea between 1993 and 1996 in relation to the trawling frequency of the sea bed and the impact on benthic organisms. ICES Journal Marine Science, 55, 403-419.

Roff, J. & Taylor, M. (2000) National Frameworks for Marine Conservation - a hierarchical geophysical approach. Aquatic Conservation: Marine and Freshwater Ecosystems., 10, 209-223.

Rogers, S., Ellis, J., & Dann, J. (2001) The association between arm damage of the common starfish, Asterias rubens, and fishing intensity determined from aerial observation. Sarsia, 86, 107-112.

Sabourenkov, E. & Miller, D. (2002). The management of transboundary stocks of toothfish, Dissostichus spp., under the Convention on the Conservation of Antarctic Marine Living Resources. In International Approaches to Management of Shared Stocks - Problems and Future Directions (eds A. Payne, C. O'Brien & R. SI), pp. pp. 68-94. Blackwell Publishing, Oxford (UK), Lowestoft (UK), 10-12 Jul 2002.

Silverman, B.W. (1986) Density estimation for statistics and data analysis Chapman and Hall, London,New York.

Vincent, M., Atkins, S., Lumb, S., GOlding, C., Lieberknecht, L., & Webster, M. (2004). Marine nature conservation and sustainable development - the Irish Sea Pilot, Peterborough.

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Figures

Marine LandscapesDeep-water channel

Irish Sea mounds

Sand/Gravel banks

Sediment wave/megaripple field

High bed-stress coarse sediment plains

Low bed-stress coarse sediment plains

Fine sediment plains

Deep-water mud basins

Shallow-water mud basins

Reefs (rocky/biogenic)

Photic Rock

Coastal Sediment

Figure 1. Marine Landscapes in the UK territorial waters of the Irish Sea.

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7°W

6°W

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4°W

3°W

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52°N 52°N

53°N 53°N

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55°N 55°N

56°N 56°N

Figure 2(a). Contours of all otter trawlers, beam trawlers and scallop dredgers >24m length during 2003 using VMS satellite data over Irish Sea Marine Landscapes (see figure 1 for legend).

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Figure 2(b). Contours of all otter trawlers, beam trawlers and scallop dredgers between 1992 and 2002 using standardised British Fisheries Protection observations.

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Figure 3. Total (a) and mean (and SD) (b) number of VMS location records km-2 for demersal gears in 2003 in each Irish Sea landscape type. Refer to figure 2a for descriptions of marine landscape types.

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bFigure 4. Total (a) and mean (and SD) (b) number of standardised overflight observations km-2 for demersal gears in 2003 in each Irish Sea landscape type. Refer to figure 2a for descriptions of marine landscape types.

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