Fish deeper.

Finding the truth from data can be harder than you think.

Camellia Williams
Oct 29, 2018 · 8 min read

How does a shellfish not much bigger than your hand cause an international diplomatic incident? When fishermen disagree over who has the right to catch them.

Fishing rights within territorial waters have always been a controversial and emotive subject, but when decisions that affect livelihoods and national economies are being made, they should be objective and based on facts. However, separating facts from hyperbole can be tricky, so where can we go to find the facts that help us understand what’s going on? And does everyone have equal access to the data that helps us understand what’s happening in our world?

This summer, a long-running disagreement between French and British fishermen over scallop dredging boiled over into rock-throwing and intimidation on the open sea. Both sides have their own story to tell, but what does the data show us, and can we even access it? As we’re about to learn, finding truth in data is sometimes harder than you think.

Let’s begin with what we know.

Every year, between 15 May and 31 October, the Baie de Seine off the coast of Normandy in northern France is off-limits to French scallop dredgers. However, the law that prevents French fishermen from catching scallops at this time doesn’t apply to British vessels. In past years an agreement has meant that British vessels larger than 15 meters in length respect the ban in exchange for extra fishing time later in the year. But this year the agreement broke down after France demanded that vessels under 15 meters also respect the ban, without any form of compensation for doing so. Since there was no longer any agreement not to, British vessels of all sizes sailed into French waters and began dredging for scallops. Upset by what they say is an unfair advantage that threatens their livelihoods, a group of French scallop fishers sailed out to meet the British fleet and the ensuing altercation was caught on a video that quickly spread online.

A video of the altercation between French and British fishermen went viral.

Over the following days, British vessels returned to UK ports with broken windows and damaged hulls, claiming that the French action was dangerous and affecting their livelihoods. On the other side of the channel, the French fishermen were claiming that the Brits were depleting scallop stocks, causing more damage to the sea bed than their own vessels do, and putting short term interests ahead of long term management plans.

There’s always two sides to a story, but how can we verify what we’re reading and hearing?

Open data for transparency.

My first port of call for information was Global Fishing Watch. Using their interactive map you can view global fishing effort and zoom in on the areas that interest you most. Vizzuality built this map and I was keen to test it and see how well it could be used to enhance a news report, or provide additional information to curious members of the public.

I began by zooming in to the area just north of the coast of Normandy and used the country flag filter so I could visually distinguish between the British vessels from their French counterparts. By doing this I hoped to get a sense of the fishing intensity here, and see if I could observe a seasonal difference in the presence of French or British boats. As you can see in the gif below, fishing is happening all year round, at varying degrees of intensity.

Fishing effort off the coast of Normandy between 1 September 2017 and 31 August 2018. British vessels are red, French vessels are blue.

Since I specifically wanted to know what activity was happening on 27 August when the altercation happened, I used the timeline along the bottom of the screen to select a specific date and period of time, in this case a 24 hour window of fishing activity.

This map here shows all the activity that occurred on 27 August. The dense cluster of red dots indicates that British fishing vessels were operating in the area.

From the Global Fishing Watch map I was able to identify the tracks of eight individual British vessels, and eight French vessels. And this is where the information I’m able to find begins to diverge from information that was later released by the UK Government. In a statement made by George Eustice, Minister for Agriculture, Fisheries and Food on 13 September 2018 in the House of Commons, it was reported that 16 British vessels and 35 French vessels had been identified from vessel monitoring information. That means my map is missing eight British vessels and 27 French vessels.

This difference could be due to a couple of reasons. Firstly, Global Fishing Watch only shows the location of fishing vessels, so any boats involved in the incident that aren’t classed as fishing vessels won’t show up here. There’s also a possibility that some vessels may have turned off their AIS (the signal that reports their location), or not have AIS installed because they are less than 15m in length and aren’t required to do so. However, given that the sea in this area is very busy that seems unlikely due to the danger of sailing ‘unseen’.

Wanting to know where they get their vessel monitoring information from, I made a Freedom of Information request to Defra in the hope that the data will be open and accessible to the public so I can compare the data to the visualisation I have. Unfortunately, the data used in their analysis “is confidential to each business concerned, and so the VMS database is not publically available.” However, they did confirm that their analysis covered the entire day of 27 August and that they detected 16 UK vessels in this time. They also provided information about the area of analysis, and it corresponds roughly with the area of my own analysis.

The British governments analysis was defined by these four Chartered Institution of Civil Engineering Surveyors (ICES) statistical rectangles.

Using the Global Fishing Watch map we can also take a poke at working out what kind of fishing was occuring at the time. Global Fishing Watch analyses the movements of each fishing vessel and it can be used to detect if it is a longliner, trawler, or purse seine. Straight lines with occasional dots indicate longline fishing is happening, while tight clusters of dots indicate that trawling is happening.

Global Fishing Watch can detect how a vessel fishes by analysing its movements. View the original image on this Global Fishing Watch factsheet.

Around the day of 27 August, the dots representing the British vessels are tightly clustered in one area, suggesting that they are trawling. The blue dots of the nearby French vessels are more spaced out, indicating that they are fishing with lines or simply passing through the area.

Now let’s take a closer look at one of the British vessels that can be seen in the video of the altercation, the Honeybourne III. The ID number of this vessel is visible in the video of the altercation so I searched for it in Global Fishing Watch. By following a link to I was able to learn that Honeybourne III is 26m long and equipped with scallop dredgers. If the usual agreement — the one where vessels over 15m respect the French ban — had been in place, it would not have been able to fish for scallops in this area at this time.

Below is a gif of its movements between 21 and 31 August. It sails into Baie de Seine, spends a little while in one area, and then leaves again after the altercation. In fact, all of the British vessels that were caught up in the incident leave the area. The tight clusters of pink dots indicate it is trawling but we don’t know exactly what for. Skippers are required by law to keep log books of what they catch and land but members of the public can’t freely or easily access this information, so unless we make another Freedom of Information request, we cannot learn what the Honeybourne III brought back to shore from Baie de Seine.

Follow the pink tracks and dots to see the route of the Honeybourne III.

By Thursday 30 August, all the British fishing vessels had abandoned the scallop beds in Baie de Seine.

The absence of red dots on the day of 30 August marks the departure of all British vessels from the area.

But what about the French? Can we say for certain that they don’t catch scallops between 15 May and 31 October? There does seem to be at least one French vessel behaving in a way that suggests it is trawling, but without the landing data we can’t say for sure which species they are catching. It would be irresponsible to make assumptions about what the vessel is doing but the French authorities could potentially use Global Fishing Watch data in their own investigation and enforcement activities.

Even though I wasn’t able to get a complete picture of what happened in Baie de Seine from the Global Fishing Watch map, it did provide context that helped me appreciate just how much fishing goes on in the stretch of water between the UK and France. Fishing within EU waters is currently managed under the EU’s Common Fisheries Policy and it’s not yet known what will happen once Brexit happens. It could be interesting to return in a year’s time and see what’s changed in terms of where everybody is fishing and to what intensity.

I’ve also learned how tricky it can be to access data and information if you aren’t part of an institution or business that’s paying for access. Global Fishing Watch is the only data platform currently available that provides open and free access to historical data on the movement of fishing vessels. The transparency and ability to download data means researchers can use the data to calculate global fishing effort and draw conclusions on what the impact might be on fish stocks.

Global Fishing Watch is only a piece of a puzzle that can tell us what’s happening in our oceans. The altercation in Baie de Seine boiled over because people were worried about their livelihoods, the right to fish, and the impact year-round dredging has on scallop stocks. To get a full picture of what’s happening in our oceans, you have to consult multiple sources of data. Some of these sources are open and easily accessible, others are accessible if you know who to ask, and others are downright opaque. If a platform that provides all the pieces of the puzzle were to be developed, it would require partnerships that bring together the data, infrastructure and expertise to make it work in a way that is useful, maintainable, and relevant. But, until there is demand for such a product, we’ll have to continue collecting all the pieces.

Please note, the Global Fishing Watch Map has been updated since this blog was researched and written, so there may be differences in the visual appearance of the map if you decide to take a look yourself.

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