Scottish Marine and Freshwater Science Volume 5 Number 17: ScotMap Inshore Fisheries Mapping in Scotland: Recording Fishermen's use of the Sea

3. Methodology

Target List

Initially, a list of 1,505 vessels to be interviewed for ScotMap was compiled. This list was based on Marine Scotland's records of Scottish registered commercial fishing vessels under 15 m overall length with an active fishing licence entitlement as of April 2011. Vessels administered in ports in Shetland were not included. During the study it became apparent that there were a few (five) other 'relevant vessels' that were not on the initial list, these having acquired a licence entitlement and reported landings from Scottish waters after the list was drawn up. The initial target list was revised to a total of 1,510 vessels.

Data Collection

Data were collected during face-to-face interviews with individual vessel owners and operators (referred to hereafter as 'fishermen'), conducted variously by Marine Scotland Compliance staff, contractors and fishing industry representatives, between June 2011 and March 2013. This period includes the Pentland Firth and Orkney waters pilot study and the subsequent roll out to other sea areas. The majority of those conducting the interviews had first-hand knowledge of Scottish fisheries and had received training in the interview methodology and recording data using the ScotMap GUI.

Prior to the interview, interviewers discussed with fishermen the aims of the study, the type of information they would be asked for and plans for subsequent data handling and treatment. This was to ensure that participants understood the purpose of the study and knew how the information they contributed would be used. A data protocol and a consent form, which were developed by the pilot project steering group, described how the data would be aggregated and set out the obligations of the data collectors and the organisations which would have access to the data to ensure that anonymity and commercial confidentiality are maintained and that fishermen's personal data are not disclosed. Fishermen were asked to sign a consent form. They were also asked for their views of the ScotMap project and these and any other comments were recorded.

During the interviews, fishermen were asked questions about their fishing vessel, crew, home and landing ports, fishing history, fishing patterns and to identify the area or areas in which they fish. They were also asked about their earnings from fishing, specifically to provide an estimate of their average annual gross earnings over the last five years and/or estimates of their maximum and minimum annual gross earnings over this period ( Table 1). Fishing areas or 'polygons', as identified by fishermen, were mapped electronically and associated information on primary and secondary (if applicable) target species, the fishing method and gear used in each area was recorded. Fishermen were asked to estimate the percentage contribution that each fishing area identified made to their gross vessel earnings, again on average over the past five years. The reference year for the study was 2011: the data collected thus relate to the period 2007-2011.

All interview data and fishing polygons were recorded using the ScotMap GUI, which was linked to ArcMap 9.3.1 and written down to geodatabases.

Table 1

Summary of data collected during interviews.

Category	Data	Description
Fishing pattern - data relating to each fishing polygon (area) identified	Species	Primary and secondary target species
	Gear	Gear class, type and gear parameters e.g. mesh size
	Percentage earnings	Fishermen's estimate of the percentage contribution each fishing area made to the gross vessel earnings, on average over the past five years
	Seasonality	Months in which fishing takes place
	Intensity	Days per year an area is fished or number of creels deployed in an area
	Map scale	Zoom level when drawing fishing polygon
Fishermen's information	Role	Skipper, owner, or manager
	Years local	The number of years fishing locally
	Age	Interviewee's age
	Fishing Association	Affiliation - member of a fishing association or not affiliated
	Producer Organisation	Member of a Producer Organisation or non-member
	Multiple vessel	Owner of more than one vessel
	Land activity	Other income sources from land-based activities
Vessel information	Vessel details	Vessel name, PLN and RSS numbers
	Length	Overall vessel length
	Power	Engine kW or horse power
	Home port	Main port of departure
	Landing port(s)	Landing or destination port or ports
	Earnings	Annual vessel gross earnings - average for the past 5 years
	Crew	Average number of crew including skipper
	Vessel years fishing	Years of fishing with this vessel
	Year built	Vessel year of build
Personal data	Personal data	Fishermen's personal data

Each fisherman interviewed was sent an individual report which included a map of the fishing area or areas identified, a summary of the information on fishing and contribution to vessel earnings they had provided and a copy of their consent form. This was part of the data process stipulated in the data agreement form. It also served as a check on the data collection and recording. Interviewees were invited to submit any amendments and revisions received were incorporated in the data set.

Response Rate

The dataset, as of July 2013, is based on interviews with 1,090 fishermen. Data from 24 additional interviews which were missing essential information or had failed for technical reasons were not included. Collectively, the fishermen interviewed identified 2,634 fishing areas or polygons. The majority of these relate to creel (pot) fishing ( Figure 1). Not all fishermen initially targeted for the ScotMap project were interviewed (72% vessel coverage overall). Some declined to take part, often on the basis that they were not actively fishing, others had sold their vessels and some could not be contacted. Not all those interviewed provided earnings information (see Table 2). Eighty six of the skippers interviewed declined to give vessel earnings information (10% earnings disclosure decline rate overall). The monetary value maps are therefore based on information from 1,004 interviews.

Data Treatment and Analysis

The interview data were subject to a series of checks, including target species nomenclature, data range, checks of vessel name, PLN and RSS numbers, duplicated polygons, inconsistencies in gear/target species combinations and polygons with no associated percentage value. In some cases fishermen were contacted to help reconcile anomalies and interview records were corrected as appropriate.

The cleansed data were then aggregated and analysed using a code developed in R to provide information on the monetary value, relative importance (relative value) and the usage (number of fishing vessels and crew) of seas around Scotland. The R code was applied to a series of gear/species combinations ( Figure 1), subsets of the data which equate to the main fisheries prosecuted by the Scottish under 15 m fleet, and to the combined data set (all gear/species combinations).

Figure 1: Gear/species polygon combinations representing the main fisheries prosecuted by the Scottish under 15 m fleet as recorded in ScotMap.

These gear species combinations comprise:

• Crab and Lobster Pots: Polygons identifying crab and/or lobster ( i.e. brown crab and/or velvet crab, green crab, spider/spiny crab, common lobster, crawfish, squat lobster) as the primary target species where fishing gear is creels (pots).
• Nephrops Pots: Polygons identifying Norway Lobster ( Nephrops norwegicus) as the primary target species where fishing gear is creels (pots).
• Nephrops Trawls: Polygons identifying Norway Lobster ( Nephrops norwegicus) as the primary target species where fishing gear is trawls.
• Scallop Divers: Polygons identifying king scallop as the primary target species where fishing method is diving.
• Mackerel Lines: Polygons identifying mackerel as the primary target species where fishing gear is lines.
• Scallop Dredges: Polygons identifying king scallop as the primary target species where fishing gear is towed dredges.
• Not Nephrops Trawls: Polygons where fishing gear is trawls and the target species is NOT Nephrops. Includes common squid (predominant target species), haddock, plaice and other flatfish.
• Other: Polygons relating to fishing for other species (includes: whelks, razorfish, surf clams, brown shrimps, pollack, cod, haddock, plaice, salmon, herring, mackerel, skates and rays, wrasse, bass, cockles, and spotted dogs) and or unusual gear/species combinations, which did not fit into any of the categories above. Because of the small number of polygons involved and the potential for identifying individuals' fishing activity, polygons in this 'other' category were not separately mapped. They have, however, been included in the combined (all interview) data set.

For monetary value, the value associated with each fishing polygon was calculated from the percentage contribution and gross vessel earnings data. Each polygon is overlaid with a grid (800 cells per ICES statistical rectangle) and the polygon monetary value is divided by the number of overlapping grid cells to equally distribute the value to all overlapping grid cells, irrespective of the extent of the overlap. This process is repeated for all polygons and the values associated with each grid cell are finally summed to produce a gridded dataset.

The analysis for relative value is similar to monetary value (above) but in this case the percentage associated with each polygon, rather than the absolute monetary value, is divided equally among the overlapping grid cells before being summed to produce a gridded data set. Treatment of the data in this way reduces the influence of larger vessels, which generally have higher gross earnings, and of those vessels fishing for relatively high value species, such as lobster and scallops, which is often evident in the monetary value analysis. Relative value provides an alternative representation of 'the value of fishing' in different sea areas. It can indicate areas of high proportional importance to large numbers of relatively low earning boats, and other small, often remote areas which are particularly important to local boats, which are often less evident from the monetary value analysis.

The number of vessels in each grid cell is the sum of the number of polygons which overlap the cell (partially or completely). Thus, if two fishing polygons associated with a single vessel overlap one grid cell the vessel will be counted twice in that cell and, contingent of the size of the polygon, a vessel will be counted in more than one cell. The numbers of vessels analyses provide information on the spatial extent of fishing as reported during interviews and are a representation of fishing intensity i.e. where most boats fish. They are not necessarily a good indicator of fishing effort, particular in the case of the combined (all interview) data set, or for fisheries where activity varies seasonally.

For the analysis of number crew, the average number of crew working on a vessel is attributed to each polygon for that vessel. The same value is then allocated to each overlapping grid cell and numbers summed to derive the number of crew associated with each grid cell.

Data were gridded using a fine 0.025 x 0.05 degree grid resulting in a resolution of 800 cells per ICES rectangle. The mean cell size was 4.20 km ² (min. 3.89 - max. 4.51 km ²). Resolution was selected as a trade-off of potential maximum resolution against appropriate level of aggregation not revealing individuals' fishing areas and reasonable data processing time. Rasters for vessel numbers and number crew were aggregated to a minimum of three vessels per cell.

In relation to the gridding technique, it should be noted that; i) the allocation of polygon values to grid squares is equal irrespective of the actual proportion of the polygon which falls within the grid; ii) the area of the grid squares based on regular latitudinal and longitudinal intervals varies with latitude; and, iii) any rounding up of values or potential inaccuracies associated with particular polygons will be propagated across different grid squares.

Evaluation of interview coverage

As indicated above, not all vessels on the initial target list were successfully interviewed for ScotMap and some anomalies in the interview data could not be reconciled. Reports from data collectors indicated variations in response rate around the coast.

To evaluate the coverage provided by the ScotMap dataset, both nationally and regionally, we used reported landings data for interviewed and non-interviewed vessels and information on port of registration and the ICES rectangles to which landings were reported. For this it was necessary to define the study area. This was done by overlapping the ScotMap interview polygons with ICES statistical rectangles. The area extends from 54 ^o30'N to 60 ^o0'N and from 7 ^o0'W to 0 ^o0', and covers about 332,619 km ² (note the area of an ICES rectangle areas varies from 3,132 km ² to 3,584 km ² over the study area). The study area with relevant ICES statistical rectangles and the draft Scottish Marine Regions ( SMRs) areas is shown in Figure 2.

Figure 2: ScotMap study area, fishery offices (or Districts), provisional Scottish

Marine Region Boundaries and overlapping ICES Statistical Rectangles.

We carried out two types of comparison:

1. Vessel and landings by registration district

Firstly, the number of vessels successfully interviewed was compared with the number of vessels on the initial target list. We also compared the total value of the reported annual landings of interviewed vessels, as recorded on the Scottish Fisheries Information Network ( FIN) averaged for 2010 and 2011, with the total value of FIN-reported annual landings of all vessels less than 15 m in length, averaged for the same period, broken down according to vessels' administration District. Results of these comparisons and the interview decline rate in each District are shown in Table 2 and Figure 3.

2. Spatial comparison by ICES rectangles

For the second spatial comparison, the total annual value of the FIN-reported landings of vessels successfully interviewed, averaged for 2010-2011, was compared with the total value of the FIN-reported annual landings of all vessels under 15 m for the same period, broken down according to individual ICES statistical rectangles in the study area ( ICES rectangles being the level at which landings are reported on FIN). Results are shown in Figure 4.

Table 2

Numbers of vessels interviewed and targeted, values of landings on FIN and interview decline rate (%) by Scottish district.

Interview Coverage
District Name	Vessel Coverage (i)	Average Landings 2010-11 Coverage (ii)	% Decline
Aberdeen	63/81 (78%)	£ 4.02M /£ 4.39M (92%)	12%
Anstruther	92/115 (80%)	£ 7.06M /£ 8.04M (88%)	0%
Ayr	41/98 (42%)	£ 4.53M /£ 6.54M (69%)	37%
Buckie	34/52 (65%)	£ 2M /£ 3.31M (60%)	0%
Campbeltown	80/125 (64%)	£ 7.22M /£ 11.88M (61%)	18%
Eyemouth	78/96 (81%)	£ 7.37M /£ 8.69M (85%)	1%
Fraserburgh	77/96 (80%)	£ 2.33M /£ 4.35M (54%)	0%
Kinlochbervie	11/20 (55%)	£ 0.56M /£ 1.05M (54%)	20%
Lochinver	8/13 (62%)	£ 0.69M /£ 1.22M (57%)	15%
Mallaig	19/39 (49%)	£ 1.11M /£ 2.38M (47%)	26%
Oban	61/107 (57%)	£ 5.9M /£ 8.53M (69%)	7%
Orkney	130/130 (100%)	£ 9.66M /£ 10.34M (93%)	0%
Peterhead	41/45 (91%)	£ 1.42M /£ 1.51M (95%)	9%
Portree	86/133 (65%)	£ 7.96M /£ 11.36M (70%)	23%
Scrabster	50/75 (67%)	£ 2.53M /£ 3.28M (77%)	1%
Stornoway	172/200 (86%)	£ 10.67M /£ 12.22M (87%)	8%
Ullapool	47/85 (55%)	£ 3.67M /£ 5.48M (67%)	13%
Total:	1090/1510 (72%)	£ 78.71M /£ 104.56M (75%)	10%

Vessel coverage (i) is the number of vessels interviewed/targeted and the % interviewed. Average landings coverage (ii) is the value of the landings of vessels interviewed/the total value of landings of all vessels under 15 m in £s millions p.a. as reported and recorded on FIN (average for years 2010 and 2011) and value for interviewed vessels expressed as a % of the total, for each administration port (District).

Figure 3: Percentage coverage of the total value of the FIN-reported annual landings of interviewed vessels averaged for 2010 and 2011, by the total value of FIN-reported annual landings of all vessels less than 15 m averaged for the same period, according to District.

Figure 4: Percentage coverage of the total value of the FIN-reported annual landings of vessels successfully interviewed averaged for 2010-2011, by the total value of the FIN-reported annual landings of all vessels under 15 m for the same period, in each ICES statistical rectangle in the study area. Provisional SMR boundaries are also shown (in black).

The spatial comparison (ii above) provides an assessment of interview coverage for different sea areas. This is more relevant to marine planning than that based on registration district and likely to be more indicative of spatial coverage because not all under 15 m vessels fish in the vicinity of their port of administration. A description of the spatial coverage within draft Scottish Marine Regions ( SMR) based on approximation of ICES rectangles is included in the discussion below. Estimates of coverage by ICES rectangle can also be used to assess interview coverage in the the Scottish Inshore Fisheries Group ( IFG) areas.

The analysis by district indicated that, overall, 72% of the vessels on the target list, which collectively account for 75% of the reported landings (average 2010 and 2011), were interviewed ( Table 2 and Figure 3). Coverage as assessed on the basis of reported landings for individual statistical rectangles varied from 48% to 100% ( Figure 4).

Regional variation in interview coverage is evident from both the district based and the spatial approach. The high decline rates and relatively poor vessel coverage for vessels administered in Ayr and Campbeltown are reflected in the low spatial coverage achieved for ICES rectangles associated with the South West and Clyde SMRs. Patchy spatial coverage in the West Highlands SMR appears to be associated with high decline rates and or low vessel coverage for Portree, Ullapool and Kinlochbervie. In contrast, very good vessel and spatial coverage was achieved for some areas eg in the Western Isles, Orkney, South East and North East SMRs.