Analysis by Charles Berkow, published 2024-10-10.

When the European Commission made its proposal for fishing opportunities, or total allowable catches (TACs) in 2025 for the main Baltic Sea fisheries in August, there were no numbers for the Gulf of Bothnia herring. The scientists working with the International Council for Exploration of the Sea (ICES) had announced back in May that their models and the data did not match, and they needed to do some more work.

ICES presented its forecast for growth of the stock in an advice sheet on 16 September, and the Commission made its proposal for next year’s TAC a week later. 

Sort of. 

The Commission proposal came in the form of a “Commission Services Non Paper”, which explicitly states that the document “cannot in any circumstances be regarded as the official position of the Commission”.  It is intended for the fisheries ministers in the Council, as a basis for their negotiations and decision on next year’s TAC.

Proposal: A massive increase, despite missed targets

The Commission proposed a TAC for 2025 of 66 446 tonnes, a 21% increase on this year’s TAC of 55 000 tonnes. 
The Commission notes in its proposal that ICES “estimates that the spawning stock biomass of the Bothnian herring is below the conservation reference point Btrigger”. This is significant, as a main objective of the Common Fisheries Policy (CFP) and the Multiannual plan (MAP) governing major Baltic fisheries is to restore and maintain “populations of harvested species above levels which can produce maximum sustainable yield”.

Advocacy and Analysis Officer Charles Berkow. Photo: Lisa Bergqvist

The Commission has apparently not explicitly asked the scientists at ICES to estimate where these levels may be. But ICES does calculate Btrigger, which is sometimes implicitly treated as the level which can produce MSY. The MAP regulation defines Btrigger as a spawning stock biomass (SSB) level “below which specific and appropriate management action is to be taken to ensure that exploitation rates in combination with natural variations rebuild stocks above levels capable of producing MSY in the long term”. It is reasonably safe to say that the target level of the CFP and MAP are a spawning stock biomass at least as large as Btrigger. And Btrigger is also used as a proxy for one of the criteria for a fish stock in the good environmental status which was to have been achieved by 2020 under the Marine Strategy Framework Directive (MSFD) of 2008.

In other words, the Commission is noting that key objectives of the Common Fisheries Policy and the Marine Strategy Framework Directive are not being met, as the spawning stock biomass of the Bothnian herring is below Btrigger. 

ICES currently estimates that Btrigger for the Bothnian herring is 613 355 tonnes. This is thus the current best guess, although there are a lot of uncertainties involved. ICES estimates that the SSB 2024 is 539 609 tonnes, that is, less than 90% of the target that was to have been achieved by 2020. With total catches at the level proposed by the Commission, the SSB would be expected to increase to 539 660 tonnes. That is, the SSB is expected to increase by less than 1/10th of one percent. ICES also estimates that even if no fishing is allowed at all in 2025, the spawning stock biomass would still be under Btrigger. 
Nonetheless, the Commission proposes an increase of the total allowable catch by a whopping 21%.

Bigger than it looks.

But it is worse than that. Due to the “inter-annual flexibility”, Member States can fish much more than the Council of Ministers appeared to have decided.

So on the one hand, a Council decision in line with the Commission proposal of 66 446 tonnes could lead to an actual TAC of well over 70 000 tonnes, including “saved” unused quotas from previous years under “interannual flexibility”. On the other hand, given that catches were under agreed TACs each year between 2021 and 2023 and are on track to being lower again in 2024, one may wonder what difference it will make in practice.

And, for that matter, why the Commission is proposing an increase. Especially in the light of the lack of progress towards meeting the goals for a spawning stock biomass above levels capable of producing maximum sustainable yield. 

Shaky numbers

But it is more complicated than that. 

The Finnish site suggests that if the utilisation of the sprat quota exceeds 100%, the exceeding amount can be registered as herring instead (as a maximum of 9% of the herring quota in question). This is consistent with the EU rules. So, if Finland reports, as it did to ICES, that it caught 55 635 tonnes of Bothnian herring in 2023, up to 9% of that might have actually been sprat.

That means that the difference between total allowable catches of herring and actual catches may be even larger than reported. 

But it also complicates estimates of the size of the stock and population growth forecasts. 

Uncertainties, uncertainties, uncertainties

In its advice for the central Baltic herring, under the heading “quality of the assessment”, ICES writes that “species misreporting of herring has occurred in the past, and there is evidence of sprat being misreported as herring. These effects have not been quantified nor included in the assessment.” That is, poor quality of data makes the assessment more uncertain.

There is no such qualifier in the ICES advice for the Bothnian herring, but given the explanation on the Finnish site that sprat may be reported as herring and the fact that herring quotas have not been filled, there may be such misreporting of sprat caught in the central Baltic being reported also as Bothnian herring. While fisheries assessments and growth forecasts are inherently uncertain and tend to overestimate the status of the stock, this accepted misreporting of species adds another layer of uncertainty.

As regards the Bothnian herring, it is even more complicated. The reason that the ICES estimates and growth forecasts for the Bothnian herring were late this year is that the numbers and models didn’t fit and ICES saw a need to revise the reference values such as Btrigger, the biomass (lower) limit value of Blim and FMSY (the fishing mortality expected to generate an increase in the spawning stock biomass, eventually to levels that can produce maximum sustainable yield). In the event, FMSY was decreased by 20%, Btrigger was increased by 15% and Blim was increased by 3.5%.

This all suggests that the actual status of the stock and estimates of what fishing pressure that might be sustainable, despite the apparent precision of the numbers, are in fact highly uncertain.

And that is only looking at the fish stock biomass in numbers, not at the population structure or the age and size structures of the Bothnian herring.

Population structure

In its advice sheet, ICES notes that the Gulf of Bothnia herring stock consists of several different spawning components. These have been shown to be genetically distinct and can have separate spawning and migration patterns. ICES concludes that the Bothnian herring is vulnerable to loss in genetic diversity. This diversity can be crucial for the ability of the herring to adapt to changing environmental conditions due, for example, to global heating.

A workshop report notes also that changes in the size of the Baltic herring could be related to changes in the composition of the spawning components. That is, sub-populations of larger herring may have been reduced more than others. Distinct spawning components can be exposed to divergent environmental conditions and respond differently. Changes in the proportions of the spawning components could be one cause of observed changes in the age and size structure of the stock.

Information on changes in the population structure is important for understanding growth and development of the stock, but is lacking.

Decimation or loss of sub-populations would in all probability reduce the future productivity of the Bothnian herring. 
In its proposal, the Commission notes the issue of the population structure and that the stock is likely to be vulnerable to a loss of genetic diversity. This is given as one of the reasons why the Commission proposal is not for an even greater increase. 

Age and size structure

The age and size structure of a fish stock is sometimes said to be an important indicator for how healthy the stock is. A high proportion of older and larger fish can be important  to maintain important ecosystem functions. A smaller proportion of older fish in a stock also means that the size of the stock is more dependent on a few year-classes and is likely to fluctuate more, depending on how successful recruitment is for a particular year-class or two.

Under the MSFD, one of the criteria for a fish stock with good environmental status is that it has an age and size structure that is indicative of a healthy stock.

The number of older fish in the Bothnian herring stock has declined during the past nine years. At their meeting in October, 2022, the fisheries ministers of a number of countries, including Sweden and Finland, as well as the Commission, expressed their concern about the size and age structure of the Bothnian and central Baltic herring. 

In response to this the Commission made a special request that ICES prepare a roadmap for possible conservation measures for Baltic herring, including looking at measures such as a closed pre-spawning spring season from 1 January to 30 June or other suitable time periods, and reducing fishing pressure including the option to not fish at all. In its reply, ICES responded in somewhat general terms to the Commission request to discuss measures such as regulations on where, when and how fishing be conducted, as well as better understanding of the population structure, causes of changes in size and others. Simulations as to how much fishing pressure would need to decline in order to allow a greater proportion of older fish to survive could be done rather quickly; many other measures would take more time and money.

In its advice sheet, ICES notes that the abundance of fish five years or older had declined over the past 8 years and was significantly lower than the average over the period 1980-2022. Also, the proportion of older individuals would remain lower even with the new target fishing mortality. In its proposal, the Commission names this as one of the reasons why it is not proposing an even greater increase.

But where the Commission writes in its proposal that “ICES notes that the number and size of older individuals in the population is unlikely to increase if the fishing opportunities were set at the FMSY point value”, in the background document to the advice sheet, ICES goes a step further: “even at the reduced Ftarget proposed here, the proportion of older fish in the stock will decrease even further”. Calculations presented in the workshop report suggest that with the new values, the proportion of older fish is likely to decline in the next few years, and remain under the average for the past 9 years, even at a much lower level of fishing than the Commission is now proposing.

Photo: Leif Ingvarsson/Mostphotos

Uncertainty, risk and objectives

Then again, given all the uncertainties, it is also questionable how robust all the numbers are. The general trend is that the stock has been more or less steadily declining for the past three decades. This, even though the fishing pressure has, for the most part, been in the zone where an increase in biomass could be expected, at least for the past 10-odd years or so. The decline in the proportion of older fish over the past 9 years is another sign that something is seriously wrong. Coupled with the vulnerability of various sub-populations and the fact that TACs are not what is limiting fishing pressure, this gives ample argument for a substantially lower TAC than the Commission is proposing.

Add to that the potential importance of the Bothnian herring as a food reserve for Finland and Sweden in a crisis, it seems the prudent proposal would be for a reduction in the TAC compared with 2024, and for a continued reduction until the stock demonstrates a sustained recovery over a number of years. It might even make sense to introduce a closure on large-scale fishing in the pre-spawning season of the first half of the year, as the Commission implied in its special request to ICES.
And this, only from the perspective of the future viability of the stock. That is, not taking into account the impact of depressed stocks and intensive herring extraction on the marine environment. 

As only Finland and Sweden have national quotas on the Bothnian herring, it is likely in practice the two of them who decide the TAC for the Bothnian herring. Last year, the Council approved much a higher TAC than the Commission had proposed. This year, there is good reason to decide on a much lower TAC than the Commission is proposing. So there is at least a theoretical potential for the two governments to take seriously the concern they expressed in 2022 and agree on a more precautionary management, in line with both the situation of the Bothnian herring, the scientific uncertainties and the objectives of the EU’s Common Fisheries Policy and the Marine Strategy Framework Directive.

Text: Charles Berkow