We are in a hangar-like building near the coast, between Oxelösund and Trosa. The lighting is dimmed and from two huge water tanks a loud, rhythmic noise can be heard. Much like when waves hit a rocky shore.
The building was inaugurated last spring and has been given the English name Baltic Waters Fish Laboratory.
- Here we have a completely unique chance to get an answer to one of biology's great riddles, says Leif Andersson and points to the water tanks where something glistens under the surface.
He is a professor at Uppsala University and has specialized in studying how the Atlantic herring has adapted genetically to cope with life in the demanding brackish water environment of the Baltic Sea. When it is caught north of the Kalmar Sound, it is often called strömming, but Leif Andersson prefers to say Baltic herring to include the entire brackish water area.
But the investigation on the agenda today is about a more widespread characteristic that is absolutely crucial for almost every species on earth: How do you know when it's time to mate?
After all, there is no point in wasting energy and effort on something so demanding if there are no others around to help, so to speak - or if the young are born when there is not enough to eat.
Here the herring can provide clues, as different stocks spawn at different times of the year. The researchers want to find out how it is that the fishermen, based on exactly the same information about, for example, the length of the days, water temperature and nutrient availability, can coordinate spawning at completely different times.
- We have shown that spring spawners and autumn spawners are genetically different and we have identified the genes that are involved. But so far we do not understand the mechanism and what happens in the fishers' brains, says Leif Andersson.
In the large water tanks behind him swim a couple of hundred Baltic herring that were carefully caught in the archipelago outside Trosa at the beginning of the summer, in connection with the spring spawning. The environment in the laboratory must now imitate life in the sea. The water temperature is carefully controlled and the dim lighting corresponds to the strength down in the depths and follows the course of the sun outside.
Once a month, the researchers rake up a number of fish to study how they change before the next spring spawn. The fish are weighed, measured and dissected. Tissue samples from the brain should provide answers to which genes are expressed in the parts that register various environmental factors and regulate the secretion of important hormones that control play.
- We hope to see results next year. These are fundamental mechanisms that play a role in how species can adapt to climate change as the relationship between temperature, light and food availability shifts. The Baltic herring will probably be forced to change spawning times as the water gets warmer, says Leif Andersson.
How it will succeed remains to be seen. The research group's other studies show that the Baltic herring has overcome many challenges in the past. But then, such rapid changes have not been required.
Recently, for example, the researchers identified a set of genes that give the eggs stronger shells, so that they do not swell and break when the water is not as salty as out in the Atlantic. And in order for the larvae to be able to get out of the eggs, there are extra genes for an enzyme that breaks up the strong bonds in the shell.
- We now know that there is significantly greater variation in the Baltic herring than was previously thought. It is a unique fish with very specific adaptations that are important to preserve because it is a key species in the Baltic Sea ecosystem, says Leif Andersson.
- In addition, we see that the fish live in smaller, local stocks that can differ genetically from each other. It is incredibly important knowledge to be able to manage the fish in a sustainable way, he adds.
Because there is a challenge that the Baltic herring has not had time to adapt to during the course of evolution. The large-scale industrial fishing. On the contrary, it carries with it a behavior that most likely makes it extra vulnerable to the kind of threat, where more than ten million fish can be swept up in a single move – the instinct to gather each year in huge communal shoals further out to sea before the stocks enter their respective home bays to mate.
It is during this time that the large-scale trawling takes place.
- Then you have no idea which local stocks you are trawling for, it will be completely random. So there is a risk that some will be taxed so heavily that they will find it difficult to rejuvenate when they return to their hometown to play, says Leif Andersson.
This is one of several examples of important factors that so far are not taken into account when fishing quotas are determined within the EU, despite the fact that they must be set on the basis of scientific advice produced by the international marine research council ICES.
This is because the mission of ICES is not about taking into account local stocks or how different parts of the ecosystem affect each other. The researchers must only calculate the total stock based on a theoretical model and answer the maximum amount that can be fished year by year.
This has led to overfishing for a long time, which has pushed the stocks of herring and sturgeon down to critically low levels. The fishing quotas have varied greatly. Every small increase in the number of fish has resulted in higher quotas the following year.
- Stocks have yo-yoed up and down since industrial fishing began, and have been around critical levels since the 1980s, says Henrik Svedäng, researcher at the Baltic Sea Center at Stockholm University.
Recently, the stocks seem to have grown a bit again in the central Baltic Sea. Ahead of the autumn's quota negotiations, ICES has therefore written in its advisory that fishing quotas can more than double next year. In its recommendation to the Council of Ministers, which will approve the quotas at the end of October, the European Commission has proposed an increase of 49 percent.
- My personal opinion, as a researcher, is that much lower quotas should have been introduced several years ago, to give the stock a real chance to recover. But it is the case that we at ICES are tasked by the EU to design the advice in this way, says Mikaela Bergenius Nord, who is a researcher at the Marine Fisheries Laboratory at SLU and for several years has been responsible at ICES for estimating sturgeon stocks in the central Baltic Sea and the Gulf of Bothnia.
Isabella Lövin (MP), who is a member of the EU Parliament's fisheries committee, believes that the EU's fisheries management must be fundamentally overhauled. Within the committee, she has drawn up a proposal for a new and more cautious model, which was voted through in parliament earlier this year. The report has then been handed over to the EU Commission, where proposals for new legislation can be drawn up. So far, there have been no reactions.
She is worried about the autumn quota negotiations.
- It would be incredibly irresponsible to fish away this opportunity for a more viable stock. We cannot continue in the same way that has led to the disappearance of cod and the collapse of the western stream stock. It's like Einstein says, continuing with the same method and expecting different results is the definition of insanity.
The Baltic herring that swim in the water tanks behind Leif Andersson are not affected by the quota negotiations. Perhaps they will contribute valuable knowledge that can be of use to their fellow species out at sea.
- It seems that spring and autumn spawners are different in success depending on climate and environmental conditions, and this is likely a crucial piece of the puzzle for their long-term development and important to take into account in management, says Leif Andersson.
He looks down into the tank. The individual fish quickly form a school when they spot his shadow.
- If the Baltic herring were to be lost, then unique adaptations and a valuable part of the biological diversity found within the herring species would disappear, he adds.
