The squid is advancing

The North Sea is one of the areas in Europe hit hardest by climate change. Higher temperatures are causing some species to disappear from the southern part of the North Sea, such as cod. "At the same time, we are finding that southern species are increasingly populating our part of the North Sea," says Lennert van de Pol, researcher at Wageningen Marine Research: “Like squid, for example.”

While the common squid (Loligo vulgaris) was once restricted to the English Channel, it is now also turning up in large numbers in the southern North Sea. According to Van de Pol, Dutch fishermen have been fishing intensively for this species in the North Sea for the past five years: "The auction price is good because it’s a delicacy in southern Europe. For fishermen, it’s a welcome source of income."

For Wageningen Marine Research, squid is a new area of research. "Our legal research task mainly focuses on classic species like cod, plaice, mackerel and sole. These have been subject to catch quotas and advice for years. But they don’t apply to squid.”

Counts show considerable differences, he says: “Catches can be much better one year than another, but we haven’t yet been able to properly identify why. It may be that stocks were low when a lot of squid were caught the previous year. However, it is also possible that a change in temperature or the food supply suddenly leads to a change in the population due to their short life cycle."

Meanwhile, economic relevance is growing, he observes: "For part of the Dutch fleet, squid is now the main target species. Because there are no guidelines for how much is 'too much', fishermen are basically allowed to catch as much as they want. That’s fine for a while, but the situation may suddenly arise when there are too few squid left to sustain the population."

The current 'free for all' status is risky, especially since very little is known about the squid. To learn more about the biology of the species, Wageningen Marine Research conducted an exploratory study for the Ministry of LVVN. This provided some interesting knowledge, according to Van de Pol: "We know they have a rather unusual life cycle compared to fish traditionally found in our part of the North Sea. Squid grow extremely fast, reproduce and then die. They will then be a maximum of one and a half years old. For other fish, the catch advice is usually based on the size of a year class. If it is larger than the previous year, then the catch advice for next year can probably be increased slightly. In the case of squid, that’s not possible because their lives are so short." 

Researchers therefore need new measurement methods. Existing models that map fleet catches during the season may be able to provide more clarity: "If a fleet fishes the same amount but catches fewer squid, then there are probably fewer squid present in the North Sea. Hopefully, we can use this kind of measurement data to capture population trends. There are currently lots of ifs and buts involved, which I want to eliminate in the coming years. We won’t suddenly know everything next year."

Wageningen Marine Research's squid research does not stop at squid: "Other species in our part of the North Sea, such as the cuttlefish or the curled octopus, should also be better monitored. That is important so that we can better understand nature. The European Marine Strategy Framework Directive also requires countries to survey the state of the sea and marine life."

The fishing technique for squid is also being investigated: "For example, we are looking at modifying fishing nets so that by-catch of small whiting can escape. That is still being developed, but it’s important if you want to manage this kind of fishery sustainably."

As a research associate, he is interested because of the unfamiliarity of squid: "They are unusual creatures, with a special life cycle. Everything we don't yet know offers potential for new research. And we are in a unique position to do that."

Once more data is available, Wageningen Marine Research will be able to provide reliable policy advice. Van de Pol: "The North Sea is expected to remain suitable, probably even more suitable for this species. So far, the squid seems to be doing well. For me, the challenge is clear: scientists, policy makers and fishermen must now work together to sustainably manage this asset in the North Sea.”

• Ministry of Agriculture, Fisheries, Food Security and Nature
• International Council for Exploration of the Sea (ICES)