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

3 Results

3.1 Units and Installation

The length of time taken to fit the units varied depending on the size of the vessel and accessibility within the wheelhouse, however the fitting times were generally in the region of two to three hours. There were often holdups in getting a date for fitting the equipment to the vessel, as this meant that the vessel had to remain ashore, and fishermen prioritised fishing. Organising fitting dates was further compounded by the fact there was only one fitter in Shetland who was very busy. In some cases this lead to a long waiting time for fitting in order to accommodate both the fisher and the fitter. There were several cases where fishermen were in the process of selling their vessel and the units were therefore not fitted until the new vessel was purchased and ready for sea. This process can take several months and in one case was further delayed by damage to a vessel through an engine room fire. A small number of fishermen were unwilling to have the equipment fitted to their vessels as they did not want to share detailed information on their fishing activity. In two cases units were fitted to vessels which had initially responded negatively. In one instance this was due to the licence holder changing their mind and in the other case it was at the request of the SSMO following a replacement vessel application.Overall the units reported consistently, especially units fitted to the more active vessels. However, after Christmas of the first year (2013) when the vessels remained at the pier for a week or two, many of the units stopped reporting their position. It is believed this was due to low battery power in the units, probably from being installed post isolator, rather than direct to the vessel's battery. By switching everything off aboard the vessel prior to the Christmas break, caused the units to drain their internal battery supply. In response to this, a troubleshooting information leaflet was sent out to all the vessels. However, anecdotal evidence suggested that in one case, where the fitting was direct to the vessels battery, there were issues with excessive battery drain resulting in the vessels battery being replaced.

3.2 Exports and Mapping

Data exported from the database and inputted directly to ArcGIS displayed an instantaneous distribution of vessel activity ( Figure 3.1). It was possible to use the speed information from the initial export to give a quick indication of fishing activity based on a speed bin value of two knots ( Figure 3.2). When this was compared with the more accurate processed fishing activity (as described in Section 2.3), it was found that the speed calculated by the units and assigned a bin value did slightly overestimate fishing activity in some instances but overall represented scallop dredging activity quite well ( Figure 3.3). For the purpose of this report, these maps display a year worth of data but in order to optimise processing efficiency, and to provide management reporting, viewing the data on a monthly basis was found to be more effective.

Figure 3.1 Distribution of vessel activity for all VMS pings in 2014.

Figure 3.2 An indication of potential fishing activity from the initial data export based on the speed bin of two knots. Information shown is for all fishing types, not just scallop dredging for the whole of 2014.

Figure 3.3 Difference in fishing activity between the speed calculated by the VMS unit and the processed speed calculation. Red areas show where the VMS units predicted fishing but the processed data did not.

3.3 Activity Outside Curfew Hours

Post processing in Excel provided a quick and easy way to view any predicted fishing activity outside the curfew hours. The information was displayed as "CHECK" as the curfew only applies to vessels dredging for scallops within the 6 nm limit. All this identified activity needs to be checked against logsheet information in order to determine if the vessel was potentially fishing illegally. This is important since most scallop vessels fish for species other than scallops which do not have restrictions on fishing times. The information is also needed to be mapped in context with vessel track information. This helped eliminate any false positive fishing activity due to slow steaming. Without vessel track information identifying slow steaming, with any confidence, would be nearly impossible.

3.4 Satellite Coverage

During 2014, a total of 243 504 pings (92%) were recorded which were not transmitted immediately, due to no satellite coverage ( Figure 3.4). On average, these generated signals were re-transmitted and received two hours 49 minutes later with the greatest difference recorded as 13 hours and 43 minutes between generated and received signals. When a satellite was located overhead, the average time to receive a ping was recorded as two seconds with a maximum receive time of 57 minutes. No information was lost during this process as the units were capable of storing the information during a delayed send.

Figure 3.4 Locations of pings sent when a satellite was overhead at the time of the ping (true, green dots) or if the data was delayed due to no satellite coverage (false, red dots).

3.5 Incorporating in Vessel Tracks

Incorporating in vessel tracks to the point data adds an additional level of quality control and clarity to the data ( Figure 3.5). Vessel tracks enable easy definition of fishing start and end times in order to assess any curfew infringements as well as differentiating fishing areas and, in some cases, the type of fishing ( e.g. scallop dredging or towing for finfish etc.). Without vessel track lines, it would be very time consuming, and in some cases nearly impossible, to determine activity such as when fishing stopped or whether fishing activity occurred within a closed area.

Figure 3.5 Vessel activity over two days showing steaming routes (yellow dots) and fishing (green and blue dots) with the vessel tracks overlaid. Land and sea references were removed to ensure anonymity.

3.6 Broken Geofences

During the course of the study six geofences were reported broken. On investigating the breaches further, one was broken by a vessel fishing for another species (most probably either whitefish or squid), and the rest were broken by vessels in transit through the areas. No closed area had a report of scallop dredge fishing within it by any vessel fitted with a VMS unit.