F

riday's announcement from ICES about next year's recommended catch quotas in the Baltic Sea is likely to cause concern among local coastal fishermen along the Swedish east coast. Not least in Gävlebukten.

Coastal fishermen there have long warned that there is an acute shortage of herring. According to many, the shortage is largely due to the large-scale trawling, which catches large quantities of herring near the coast every year.

ICES recommends that the total allowable catch (TAC) for 2021 be increased to between 91,494 tonnes and 117,875 tonnes. Following the upper limit of the Fmsy-range would result in an increase of just over 80 percent compared with last year's advice. For 2022, ICES recommends that the TAC be subsequently reduced by five percent (86,729 – 111,345 tonnes).

– The increase is due to the fact that we have used a new model for stock analysis that provides a better and safer picture of the stock, and allowes us to provide advice based on Fmsy, and not, as before, on the precautionary principle, says Mikaela Bergenius Nord, researcher at the Swedish University of Agricultural Sciences, Department of aquatic resources (SLU Aqua), and chairman of the ICES working group WGBFAS, which works with advice for the Baltic Sea.

Lack of larger herring

Previously, there has been a lack of sufficient data and knowledge to make a good stock assessment of the Gulf of Bothnia herring. But now a working group within ICES has used a new model, the Stock Synthesis Assessment Reference Model (SS3), and according to the SS3 analysis, the stock is significantly larger than previously thought.

Coastal fishermen in the Gulf of Bothnia have difficulty finding any herring. ICES says that there is plenty, and that the stock can withstand increased fishing. How does that work?

– This is mainly due to the fact that the size of herring in the stock has decreased. There are fish, but not the bigger fish that part of the fishing wants, says Mikaela Bergenius Nord.

Fish stocks that have a natural distribution of both smaller and larger individuals are in much better shape than those who don’t. If the large individuals are removed, the population weakens.

The case of the herring in the Gulf of Bothnia exposes the shortcomings that exist in today's fisheries management and advice, says Mikaela Bergenius Nord.

– Commercial fishing is generally aimed at the larger and older individuals in a stock. As you start fishing more and more, the size structure of the stock shifts towards smaller and younger individuals. But despite that, the stock can still be considered sustainably managed according to MSY, she says.

Focus is on the MSY target

MSY is a cornerstone of the EU fisheries management, and aims to maximize catches from an individual stock, with the smallest possible margin. Today's MSY management and advisory services do not take into account the size distribution of the stocks, according to Mikaela Bergenius Nord.

– In both the MSFD and the EU's common fisheries policy, there are management targets for size structure, but when ICES is commissioned by the European Commission to advise on commercial fishing, there are no questions relating to these targets. The focus is only on the MSY target, she says.

But if a fishery risks removing all large individuals and thereby weakening the stock - can it then be called sustainable?

– That is the key question; what is defined as sustainable? says Mikaela Bergenius Nord.

She would like to see the management goals and advice changed so that they take greater account of the size distribution of the stocks, among other thing. But the work of implementing such changes place at EU level, she says.

– As researchers, we can point to the problem, but then Sweden must take the issue further to the EU Commission.

The fishing pressure is underestimated

Fisheries researcher Henrik Svedäng at the Baltic Sea Centre is very critical of ICES’ latest TAC recommendation for the Gulf of Bothnia herring, and calls it "a major risk-taking".

– The proposed increase in fishing poses a threat to the entire marine environment in the Gulf of Bothnia, he says.

He does not believe that the lack of larger herring in the Gulf of Bothnia can be blamed on fishing conducted according to MSY, but rather on the fact that the estimated level of sustainable fishing mortality (Fmsy) is too high.

– If a fish stock is actually fished on a correctly assumed Fmsy, the stock will still have large individuals, he says.

As the Gulf of Bothnia herring stock has normal growth and is growing as it should, the probable explanation behind the lack of larger herring is rather that the fishing pressure is underestimated, according to Henrik Svedäng.

– This means not only that the degree of exploitation has been underestimated but also that the size of the stock has been overestimated. An increased TAC during this year could lead to real overfishing, well above MSY, he says.

Subpopulations might be depleted

Henrik Svedäng points out that the latest stock estimate with the SS3 model does not take into account the latest scientific findings on the genetics of the Baltic herring and the existence of local subpopulations and stock components.

– Recent studies show that the stock is divided into several subpopulations – also between the Bothnian Sea and the Gulf of Bothnia, the areas that a few years ago were merged into one "stock". An increased fishing pressure risks knocking out subpopulations one after the other. Especially since most of the catches are taken by some really big trawlers, he says.

– It can also be an important reason why coastal fishermen have difficulty finding herring.

Mikaela Bergenius Nord agrees that there is a certain risk that local subpopulations will be fished down. But according to her, more knowledge is needed – and she hopes that new research efforts will be able to provide just that.

– We know that there are local spawning stocks. But we do not know enough about how many there are and how they mix with other local spawning stocks. We also do not know exactly where to draw the line for when a genetic variation should have an impact on how to fish and how we choose to divide the stock. Where do you draw the line? she says.

The central Baltic herring continues downwards

The trend remains negative for the central Baltic herring stock. ICES recommends a TAC reduction of 36 percent for 2022. The stock is considered overfished, with a fishing pressure that for many years has been well above the limit for sustainable fishing (Fmsy). The spawning stock biomass has decreased by about 80 percent since 1974 and is now close to the critical limit where reproduction risks being damaged (Bpa).

– As the herring in this huge sea area is divided into a probably large number of subpopulations, great care must now be taken when setting TAC for the commercial fisheries, says Henrik Svedäng.

According to him, the is great risk of local spawning stocks being wiped out by large-scale fisheries also in the central Baltic Sea.

– Most of the catch is taken by relatively few but large trawlers. By putting their fishing pressure on individual stocks, they can cause a depletion situation where subpopulations disappear or become so decimated. If this happens it will many years for them to recover, Svedäng says, and continues:

– The recommended 36 percent reduction in TAC for next year is not in line with the precautionary principle. Decades of environmental work can now be wasted and we run the risk of getting a completely changed ecosystem, where herring will be lacking in large parts of the Baltic Sea.

No new strong year class

Last year, ICES signaled that there was hope for a new strong year class from 2019 - similar to the one that came in 2014/2015.

– Unfortunately, in this year's estimates we can’t see it anymore, says Mikaela Bergenius Nord.

According to her, there is also a lot of uncertainty in the estimates, which among other things may have to do with incorrect reporting.

– The misreporting of catches of herring and sprat is a problem. We are now working on developing a sampling program to be able to get a better idea of ​​this. But it is not an easy thing to estimate, she says.

A more ecosystem-based management is needed

ICES 'latest TAC advice confirms the overall situation from last year, namely: it looks bleak for most commercial fish stocks in the Baltic Sea.

It is becoming increasingly clear that more a ecosystem-based management and advice is needed, according to Maciej Tomczak, researcher at the Baltic Sea Center.

– In general, much more consideration must be given to how the ecosystem actually works in the open sea and in the coastal environments, he says.

Among other things, he calls for a multi-species management, which can handle the fact that different fish species do not live in isolation in the Baltic Sea but interact and influence each other.

– More needs to be done to prevent overexploitation and prevent ecosystem damage. A more spatially detailed management plan is required, which also includes the coastal areas, says Maciej Tomczak.

Text: Henrik Hamrén