Photo: Tobias Dahlin/Azote.

With the dramatic decline of the iconic Baltic cod, the humble herring has sailed into prominence, both commercially and politically. In the species-poor brackish Baltic, it has always been important ecologically. Now, the largest of the stocks, the Central Baltic herring, is also plummeting. Why?

The decline of the herring

In 2017, scientists at ICES estimated that the 2014-year class of the Central Baltic herring (CBH) was more than twice as large as any other year class since at least 1974. In 2020, ICES estimated that the 2019 class was also unusually large, though nowhere near as good as 2017.

Comparison of the annual estimates of the spawning stock biomass (in tonnes) of the Central Baltic herring stock, made between 2016 and 2020. Note that MSY Btrigger and Bpa are at the same level. Source: ICES.

This year, ICES recommends that fishing quotas for the CBH for 2022 are slashed by a whopping 36%. That comes after a similar 36% cut accepted by EU ministers for 2021. And a 10% cut for 2020. And a 26% cut for 2019.

In numbers, ICES recommends that catches be between 52 and 72 thousand tonnes in 2022. This is a lot less than the 2018 catch of 244 thousand tonnes.

Is it the politicians’ fault - again?

The decline of Baltic cod can be linked to short-sighted politicians ignoring scientific advice and allowing overfishing, thereby depleting a stock.

But this is not really the case for the Central Baltic herring. In fact, EU fisheries ministers can with some justification claim that they have actually followed the ICES advice at least since 2014. That is when the latest decline in spawning stock biomass (SSB) began.

At least, if you just look at the numbers. If you read the fine print in the advice, there was an important warning that the politicians and their advisors missed – or ignored.

In 2018, ICES wrote the following in its advice:

“It should be noted that the large 2014 year class will be the main contributor to the yield in 2018 and 2019 and SSB in 2019 and 2020, and no substantial new incoming year classes are predicted. It is uncommon to see such large contribution of one year class to the SSB as seen in the short term prediction for 2019 and 2020. Three last year classes are below or at the average and if such a situation continues, a marked decline in biomass development can be expected.”

Implicitly, ICES thus presented the politicians with a choice: take a short-term view and fish up the bumper 2014 class, or think of the longer term and fish less, so that the year class can grow and perhaps give a stronger basis for future year classes of herring.

In effect, as so often, the EU politicians chose the easy way out and decided on catch limits (Total Allowable Catches or TACs) in line with the upper limit of the ICES advice.

Blame the Russians?

Russia also fishes on the Central Baltic herring. But the Russian minister is not at the table when EU ministers decide fishing quotas in October. Russia and the EU have their own negotiations, usually during the summer. In recent years they have disagreed.

According to an old agreement between the EU and Russia on allocation keys for shared stocks, Russia should take 9.5% of the total quota. The EU keeps its TAC at 90.5% of the ICES advice or lower. But Russia wants more than 9.5% of what ICES recommends, and it takes it. In particular, when the EU Member States made major cuts to their CBH quotas in 2019 and 2020, Russian catches actually increased.

Still, the excess Russian catch is a small share of the total catch. This cannot explain where all the herring went.

Did the fishers take too much?

Another suspect is the fishing industry. But reported catches have been within the totals allowed by the politicians and managers. And these TACs in turn, as seen, have been within what the scientists have recommended (with the exception of the Russian catch).

The key word is reported catches. ICES informs us regularly that there is evidence that the big pelagic vessels misreport what proportions of herring, sprat or other species they catch in their trawls. ICES explains that this may affect the quality of the assessment, though it doesn’t try to guess by how much.

It is the politicians and managers who have encouraged the development towards larger, newer, more efficient vessels. It is also the politicians and managers who are responsible for monitoring and controls – or lack of them. And it is the Swedish authorities that have granted exemptions to the industrial trawlers to fish close to the shores.

Of course, outsiders cannot tell to what extent these decisions have been influenced by the industry. But it is a safe bet that they were not made in the face of opposition from the loudest voices of the industry. No one knows what effects these decisions may have had on spawning or on local sub-populations, not to mention the environment.

Did the scientists get it wrong?

With hindsight, scientists now say that they seriously overestimated the size of the CBH recruitment and stock during many of those key years. Estimates of the important 2014 year class have been successively revised downwards from 61 million tonnes 2017 to 31 million tonnes now.

How could the scientists get it so wrong?

One reason is the decline in the cod. In 2020 the scientists concluded they had overestimated how much herring cod ate. So, they adjusted the model, and when the estimated number of herring eaten by the cod went down, the estimate of how many herring were left also went down.

But that still only explains part of the difference. Other explanations for the uncertainties could be a decline of subpopulations, disruptions caused by intensive industrial fishing or various more or less natural causes.

It is simply very difficult to estimate how many fish there are in the sea. Baltic herring is said to be one of the most thoroughly studied species in the world. But an extra challenge for the scientific models is that the Baltic, as a largely enclosed, shallow, brackish sea with over 85 million people in the catchment area is also particularly sensitive to large-scale environmental changes such as disruption of the nutrient cycle or global heating.

Prudence suggests a bigger precautionary buffer

EU and Russian ministers need to realise that fisheries science is more uncertain than it looks. The Baltic Sea Centre has elaborated on this in a recent policy brief.  

It is much more harmful to the stocks and the marine ecosystem to overfish than to than to leave more fish in the sea. Reasonably, given the uncertainties, politicians and managers should therefore not aim for fishing at Maximum Sustainable Yield as they have in the past, but substantially under.

The EU’s Multiannual Plan for the Baltic herring, cod and sprat gives managers the option of using a precautionary buffer, technically called F-lower. They should take that option, consistently. And if things look bad enough, like they now do for the Central Baltic herring, they can and should go even lower.

With so much at stake and so many uncertainties, it simply makes sense to be prudent.

Text: Charles Berkow