Scottish Marine and Freshwater Science Vol 6 No 13: A multidisciplinary approach to collection and use of VMS data from an inshore scallop fishery

4 Discussion

This study has clearly demonstrated that Succorfish SC2 VMS units have the potential to operate and deliver high quality data within the inshore environment in remote areas of Shetland. Fishermen were largely positive about the scheme and its benefits both in terms of improved fisheries data for inclusion in stock assessments and marine spatial planning, but also in terms of enforcement of the SSMO regulations.

Entering into a data sharing agreement with fishermen was a valuable exercise as it not only provides them with confidence that their data will only be used for the agreed purpose but also because it sets up a line of communication for any future use of the data. This means that the value of collecting, analysing, and retaining such data can be communicated to fishermen each time they are approached for its future use. This is particularly pertinent in the marine spatial planning context.

4.1 Units

The use of the mobile phone network did not compromise the quality of the data received as the units were found to be able to store and re-send data at a later date without any loss of information (see Section 3.4). In 2014, this applied to 92% of all pings with information being stored on average for nearly three hours before re-sending. The ability to be able to store information for prolonged periods without losing any data is essential in remote locations and when operating close to shore where a signal (satellite or mobile phone) may be obstructed by the local terrain. The use of mobile phone technology is also an important consideration should the fishermen ever be asked to bear the cost of reporting, with mobile phone reporting costing less than a third of the satellite and mobile combination.

Unit reliability was a major initial issue with many units failing to report positional information. The problem was identified as most likely due to the units being installed post isolator causing the internal battery to drain when the main power was switched off for long periods. Succorfish recommend the units are connected direct to the battery but in many cases the fisher did not want this in case the unit drained the vessel's power supply. Each unit is rated as drawing on average 1 Amp hour a day from the vessel's battery. At this rate, the units would drain a 12 V battery if left for more than three months. As this study relied on volunteers, it was not possible to enforce how units were wired up to the power supply of the vessels. The dashboard of the online database was the quickest way of determining if a vessel was reporting or not. This was hugely advantageous as it meant that any power issues could beaddressed quickly however, it also relied on someone logging on and checking the database on a frequent basis.

4.2 Data Processing

A ping period of ten minutes provided high quality data outputs enabling easy interpretation and subsequent mapping of fishing areas. The initial export from the database, and subsequent import to ArcGIS, displayed vessel movements at different speeds and was relatively straight forward to do. It gave a good indication of fishing location, based on the defined speed bins, and it would be possible to extract information on any vessels fishing outside of the curfew, although this would be quite time consuming without further processing steps.

Further data processing in Excel and ArcGIS added an extra confidence in the outputs and provided additional capabilities as well as added value to the data. Most importantly, it allowed the information to be differentiated into fishing methods, focussing attention on scallop dredge activity only. In addition, further processing enabled vessel tracks to be created which helped to differentiate between fishing activity and natural slow vessel movements. Without vessel tracking information, an increase in false fishing areas or activity would be reported. This would have a knock on effect on management and compliance of curfew periods or closed areas with an increased number of investigations having to be carried out into legitimate activity. Without carrying out further processing, it would not be possible to use the information in spatial management plans for fisheries, stock assessments, or in marine spatial planning. We would recommend that the data is processed fully, separating out fishing types, creating vessel tracks, and identifying fishing activity. This reduces the demand on managers and compliance but increase the reliability of the information and correspondingly increases the level of trust and 'by-in' from the fishers.

4.3 Data Applications

The quantity and complexity of VMS information incorporated into a stock assessment can vary widely depending on the underlying data available on vessel landings, activity, the resolution of the information, and how that is reported. Shetland operates a logbook system based on a 5×5 nm grid (this equates to, 36 Shetland squares within one ICES square). Information reported in the logbooks includes vessel information, the square fished, hours towed, number of dredges used, and the quantity landed for each trip. By carrying out post processing of the VMS data, as discussed above, it would be possible to incorporate logbook information with the VMS. By incorporating the two datasets, it would be possible to provide ground-specific information on landings, effort, and landings per unit effort ( LPUE), rather than square-specific information. Combining the data provides an increased level of accuracy as the VMS provides high quality information on both the areas fished and the time spent fishing those areas. This may not always correspond with what the fishers report in their logbooks. The data produced by the VMS units has already been used to more accurately define the scallop grounds around Shetland and this is being incorporated into the design of a scallop survey. The expected outcome of the survey is a biomass estimate for the fished population of scallops in Shetland. This will then be able to feed into the management process through the setting of reference points.

The data collected can also effectively support spatial management of scallop fisheries. Incorporated into the database is the ability to define no-go areas, termed geofences, which, when 'broken' (when a vessel moves into the geofence area) by the vessel, the database registers a message on the dashboard. Broken geofences can also be downloaded as a specific export from the database. Geofences do not rely on any speed information so a broken geofence occurs every time a vessel passes through the designated area, irrespective of the vessels' activity. If vessels are permitted to pass through the specified area, as is the case for the scallop dredge closed areas in Shetland, a potentially high instance of broken geofences may occur, depending on their location, and each report of a break would have to be investigated. This tool would be highly beneficial in vessel exclusion areas where a total ban on all vessel movement within an area is in place. In areas which permit vessel through traffic but no dredging, the tool provides a quick way of identifying vessels that may be breaching a ban on fishing in specific areas. By carrying out further processing and displaying the fishing pings and vessel track information in ArcGIS, any illegal fishing within a closed area is easily identifiable.

The data collected through the VMS units has been integrated into the SSMO Management Plan and decision making process and ongoing monitoring of their Spatial Management Plan and Code of Conduct. Examination of the VMS data is a standing agenda item for the SSMO Advisory Group which provides recommendations to the SSMO Board. Should there be any evidence of fishing activity within the closed areas or during the scallop curfew hours within the six nautical mile limit this will be discussed and reported to the board for action.

4.4 Future Considerations

Vessels which participated in the study have retained the VMS units aboard with data still being transmitted and logged. Information obtained from the VMS units will be used for compliance, fisheries spatial management, stock assessments, marine spatial planning, and scallop survey design. The SSMO have paid for an initial years-worth of air time while they finalise their management measures for VMS units and the NAFC Marine Centre have continued to manage and process the data providing the SSMO with regular updates.