Fish without borders: can the UK claim their fish after Brexit?

The upcoming Brexit has European fishermen worrying that they cannot continue to fish in British waters as they have been doing for centuries. If British waters would truly be closed to European fishermen, it would deal a strong blow to the European fisheries, since many fish are caught in British waters. Here we raise the questions: do fish really care about these country borders, and is it valid from a biological viewpoint for the UK to claim ‘their fish’?

Even though European fishermen have been fishing in each other’s waters for centuries, the worry of European fishermen is not unfounded: the United Kingdom (UK) has already announced its withdrawal from the 1964 London Fisheries Convention, which allows countries to fish in each other’s coastal waters. However, in a separate agreement, members of the European Union (EU) agreed to manage fish stocks together by dividing fishing quota among member countries and by allowing member countries to fish within 200 nautical miles of each other’s coasts. So far the UK has made no accouncements of withdrawing from this agreement, but one of the pillars of the Brexit campaign was for the UK to gain back control of the fish in their waters.

In collaboration with the Danish Pelagic Producers Organisation, we wanted to find out to what extent it is valid for the UK to claim that the fish in their part of the North Sea is actually ‘their fish’. Despite that many fish are caught in UK waters, species such as herring and mackerel are highly migratory. Therefore, we wanted to know where Danish fishermen catch their herring and mackerel, and where most herring and mackerel reside in the North Sea throughout their lifetime.

As expected, the majority of herring and mackerel landed by the Danish fleet during the past 10 years was caught in UK waters (Figure 1). Interestingly, another fair share was caught in Norway. Norway is not an EU-member, but still has fisheries agreements with the EU, thereby recognizing that cooperation is needed to manage shared fish stocks sustainably.

Figure 1. Top: the mean annual landings of herring and mackerel (in tonnes) caught by the Danish fleet in summer between 2007 and 2016. Bottom: the mean annual number of young herring and mackerel caught per hour of fishing by scientific research vessels in summer between 2007 and 2016. Young herring are below 20 cm and young mackerel are below 25 cm. The black lines are the 200 nautical miles zones of countries.


When we looked at the distribution of herring and mackerel in the North Sea using data collected by scientists, we noticed that these fish do not spend their entire life in British waters. For example, whereas larger mackerel occur throughout the North Sea, young mackerel remain in the shallow southwestern North Sea during the summer months (Figure 1). Similarly, the majority of small herring can be found in the southeastern North Sea, whereas the adults reside in the western part that belongs to the UK. When herring spawn their eggs into the water, the eggs and young fish larvae drift with the currents to the eastern part of the North Sea. There, they grow up in the shallow and safe waters of the Netherlands, Germany and Denmark. Only after 2 years, when they have grown big enough, do they return back to the UK waters in the western North Sea where they are fished upon.

These migrations across country borders put into question how fair it is of the UK to claim that the adult fish that reside in their waters belong to them. Not surprisingly, fish do not care in which country they reside or where they are caught. They do care about where the best conditions for them are. As we have shown here, it is thanks to the nursery waters of other European countries in the southern North Sea that young herring and mackerel can grow big enough to migrate back to more northern waters in the UK. A full access restriction to UK waters for other European fishermen does not seem fair from this point of view.

Besides fair agreements regarding who can fish what and where, it is in everyone’s favor that the shared fish stocks in the North Sea remain at sustainable levels, so that they can be profitably exploited in the future. We need to learn from our mistakes of the past, and accept that fair international agreements are necessary for the sustainable fishing of shared fish stocks. Let us hope that the UK will continue with international cooperation on managing European fish stocks, as the EU and Norway have already been doing for decades.

Tags: Fisheries, Mackerel, Management, Brexit, Herring By Esther Beukhof, Rob van Gemert
Published Aug. 25, 2017 10:39 AM - Last modified Aug. 25, 2017 10:39 AM