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The science of sustainable seafood, explained

The state of UK stocks is better than Oceana’s depiction

Last month, Oceana made waves across the pond with Taking Stock: The State of UK Fish Populations 2023, a report that painted a negative picture of fishing in UK waters. The report and press release excluded important context that misled mainstream media into echoing the doom and gloom narrative.

The tagline of the press release was, “Half of the UK’s key fish populations are overfished or in a critical state,” which requires some unpacking. Two main variables determine fishery sustainability: the stock size or biomass (B) and the rate of fishing (F). Fishery managers aim for a population size that produces maximum sustainable yield (MSY, in this case, BMSY) and an amount of fishing pressure that produces MSY (called FMSY).

By traditional scientific definitions, a stock below BMSY is labeled “overfished,” while a stock being fished harder than FMSY is “experiencing overfishing.” A stock that is both overfished and experiencing overfishing is unsustainable, but stocks that meet one of the targets are acceptable. For example, if a stock is overfished (i.e., below BMSY) but fishing pressure on that stock is below FMSY, managers are doing their job to rebuild the population. Stocks fished a bit harder than FMSY but above BMSY are not in immediate danger—there is simply a bit more fishing pressure than would maximize the long-term yield. More in our explainer of overfished, overfishing and rebuilding stocks.

In the report, Oceana uses its own definitions. They call stocks that are experiencing overfishing (FMSY too high) “overfished” and stocks below BMSY “critical.” None of the UK’s top 10 stocks highlighted in the report are both “overfished” and “critical.” Take a look at Figure 13 from the report found on page 56. Of the top 10 stocks, only one (North Sea Cod) is below BMSY (“critical” by Oceana’s definition, overfished by scientific definition) and is on track to rebuild as fishing pressure is below FMSY. Saying half of the top 10 U.K. stocks are “overfished or in a critical state” means little when you dig into the definitions.

A figure showing the top 10 fish stocks in UK waters.

UK fish stocks were overfished for decades, but with improved regulations starting in the 1990s, fish populations have bounced back. Since 2013, UK fish production has increased every year, and overall fish populations are at their highest levels since the 1960s.  

Southern Atlantic cod stocks have not recovered at the same rate as other species, but they have proven to be highly sensitive to water temperatures and have migrated north as the ocean has warmed. Cod stocks at higher latitudes are more robust than in decades.

Oceana’s report fails to acknowledge the progress or regulations that have been working for decades. Their press release was picked up by several UK outlets and spun into clickbait headlines that have frustrated fishery scientists. Michel Kaiser and Paul Fernandes, two professors at Heriot-Watt University in Edinburgh, wrote to The Times responding to the recent coverage. We are reposting their words to bring more awareness (even leaving in their British spelling!):

Ben Cooke’s article ‘So long, all the fish?’ relies heavily on the opinion of a former journalist and environmental campaigner Charles Clover and a report by Oceana. Not surprisingly the complexity behind the figures is ignored.

It is true that until the mid-1990s stocks in northern Europe were frequently fished at levels higher than the scientific advice. Since then improvements in scientific advice, laws, enforcement and political ambition have led to reductions in landings (UK production) which are indicative of effective management and adherence to catch limits. This underpins the up-tick in UK production (shown in the article’s main figure but ignored) that has occurred since 2013 to higher levels of production as stocks recover. The Oceana report, fails to mention that the adult biomass of many of the stocks of interest to the UK are at the highest levels since the early 1960s: adult biomass of North Sea plaice is currently just under 1 million tonnes, double the amount that is needed for sustainable exploitation; North Sea haddock adults amount to 400,000 tonnes, also double the sustainable amount; North Sea whiting just under 300,000 tonnes (double), North Sea herring 1.2 million tonnes (at the sustainable amount), and there are over 6 million tonnes of blue whiting (3 times more), and almost 4 million tonnes of mackerel (1.5 million tonnes more than sustainable limits).  Many of the prawn stocks are at high levels up to twice those required for sustainable exploitation.  These figures, (from the International Council for the Exploration of the Sea) do not paint a picture of UK stocks being in a “critical” state. The article wrongly states that the UK Government is responsible for setting quota, it does not, this is a negotiation with the EU and other states to set catch limits.

It is not clear why cod are not recovering in UK waters, when some other similar species, such as hake, have.  Part of this is due to environmental (climate) related issues, as there are healthy and very large cod stocks around Iceland, Greenland and Norway in colder waters which suit the physiology of the cod better than our warming seas. The return of hake to the North Sea may also have led to competition with cod as they both feed on fish close to the seabed.  There are now over 200,000 tonnes of adult hake around British waters, compared to less than 50,000 tonnes in the 1990s.  The Clyde Sea has plenty of fish biomass, particularly of sprat, but the fish remain too small to catch and hence there is no viable fishery at present. The idea that the UK Government is too scared to remove fishing opportunities is entirely misleading given that more than 30% of UK waters are locked up in protected areas with increasing levels of management that are activity removing certain types of fishing from areas of UK waters. It seems odd for The Times to present the views of a well-known environmental campaigner without seeking to scrutinise the evidence, which only adds to public confusion about these issues.

Picture of Max Mossler

Max Mossler

Max is the managing editor at Sustainable Fisheries UW.

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