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

2 Materials and Methods

2.1 Units and Installation

The Succorfish SC2 VMS (hereafter referred to as " VMS") unit is a single box with no external antenna which is hard-wired to the vessel. The units incorporate dual Iridium satellite and GPS/ GPRS/ GSM mobile technology to provide accurate positioning to within two metres. Outputs from the unit for each ping include; vessel name, position, generated date and time of ping, speed, course, whether a satellite was overhead at the time of the ping, and the date and time the ping was received. The unit calculates instantaneous speed for each ping and then assigns a 'speed bin value' in knots starting at 0 knots with incremental increases of 2 knots thereafter. These 'speed bin values' are what is exported by the system.

VMS units were offered to fishermen on a voluntary basis with the most active scallop dredge vessels approached for inclusion in the project. There were 36 SSMO licenced vessels which fished for scallops, all of whom were written to regarding the project and its aims. Of these, 23 make the majority of landings and these vessels were actively approached to have units fitted. The first unit was fitted in Shetland in April 2013 with a total of fifteen VMS units fitted throughout the period of the project. A data sharing agreement (Appendix 1: Data Sharing Agreement) between the NAFC Marine Centre and each SSMO licence holder participating in the study was carried out in order to provide the fishermen with security as to how and when their data would be used. Fishermen were also provided with log in details for the Succorfish online database (see Section 2.2) so that they could view their own activity online.

Initially the units were set to report every three minutes but this was later changed to every ten minutes with locational information stored in a secure database and accessed via the internet. The change in ping frequency from three to ten minutes was an operational decision in order to maximise the quantity of information relevant to the vessel activity and the aims of the project without losing valuable information on fishing activity. Pings were transmitted via satellite but in the event of no satellite coverage, the units stored the information until it was possible to re-transmit the data. This eliminated any information loss due to loss of signal. 2.2 Database

The Succorfish secure online database provided several screens of information with the main screen, the 'Dashboard', summarising events from each VMS unit. Summaries included all vessels not reporting, power and tamper events, and any "Broken Geofences" (a user defined area, e.g. areas closed to fishing). In addition, the database contained information on the 'Assets' (vessel information), 'Monitoring' (the map interface), and an 'Administration' section. Monitoring provided real time map displays of vessel locations which could be back dated by two days. In addition, it was possible to select specific geofences for display providing real-time and short-term historical views on vessel movements and potential interactions with closed areas (geofences).

2.2.1 Data Export

Exporting the data was carried out through the Administration section of the database using a user friendly interface with the ability of selecting specific vessels and time periods. The default export related to each vessels' coordinates and the data was exported as a comma separated (*.csv) file. Each export contained eight fields per ping corresponding with the vessel's name, generated date and time, coordinates, speed, course, whether a satellite was overhead at the time, and a received date and time (see also Section 2.1).

Additional exports were also possible and included:

• geofence breaches,
• any events listed ( e.g. low battery, tamper events, etc),
• instances of units not reporting.

2.3 Data Processing

After the initial database export, a simple transformation could be applied to the csv file allowing a point shapefile to be created and used in Arc GIS. However, this information provided details on the vessels' distribution showing all movements including steaming and dredging, as well as all types of fishing ( e.g. scallop dredging, squid or finfish trawling, etc). Although the original export contained information on a vessel's speed, the value exported was assigned a specific number (a data bin which had an incremental increase of two knots per bin, see also Section 2.1) rather than a calculated speed between pings. In order to obtain good quality information on whether a vessel was fishing or not, additional processing was required in Excel and the mapping package ArcGIS. Additional processing increased the reliability of the data and enabled vessel tracks to be incorporated onto a map which added an extra level of quality control and interpretation.

The exported csv file was converted to a point shapefile in ArcCatalog. In order to obtain more detailed information between consecutive pings to better evaluate vessel activity, additional fields were calculated. Using the Tracking Analyst extension and the tool "Track Intervals To Features", four additional fields were calculated between consecutive pings for distance, duration, speed, and course. The calculations were based on a formatted time stamp and subdivided by vessel name. This data was exported from ArcCatalog and saved as an Excel file.

Two additional columns were created in the Excel file titled "Activity" and "Curfew". Vessel activity was categorized, based on the above calculated vessel speed as; "Stopped" (≤0.5 knots), "Fishing" (between 0.5 and 2.5 knots), or "Steaming" (>2.5 knots). If the predicted activity was "Fishing" outside the curfew hours of 6 a.m. to 9 p.m., the text "Check" appeared in the Curfew column. These two columns provided a quick reference to the data but still required a quality control via mapping in ArcGIS. The processed information was converted to a shapefile and vessel track lines were created, using the Tracking Analyst extension, which created a straight line between each consecutive ping. By displaying the point data by Activity and combining vessel track information it was easy to identify genuine fishing activity and eliminate any 'rogue' values when in port or steaming.