The issue of the red king crab in Norwegian waters is a spiny one. It is an invasive species that disrupts lucrative cod fisheries. It has a poorly understood impact on local ecosystems. But it has also recently become a revenue-generating catch for the country – and one that locals would like to be able to better export live.
At the crux of both of these issues – the crab’s spread and its maintenance in captivity – is the question of optimal water temperature. Local scientists want to know more about how temperature impacts the crab’s health and growth.
That is why the Norwegian government is funding new research, conducted in part by Colorado State University Professor of Biology Don Mykles. Mykles, also director of the University Honors Program, runs the CSU Crab Lab in the biology department and is an internationally renowned expert on the genetic control of molting and growth in crabs. He has worked on temperature stress in land crabs and other crab species.
“We have identified molecular markers that are related to temperature stress” in our crab research at CSU, Mykles said. “So we can use those markers to study the effect of temperature on molting and growth” on other crabs. Including those living deep underwater in the Arctic Circle.
The red king crab (Paralithodes camtschaticus), also known as Alaskan king crab, lives up to its name. This burgundy-colored crustacean can grow to be nearly 6 feet in leg span. And it is prized for its meat, making it a sought-after export. These crabs, though native to the Bering Sea off the coasts of Alaska and eastern Russia, were introduced to the climactically similar Barents Sea thousands of miles away by Soviet scientists in the 1960s.
The cold water crabs thrived in their new ecosystem, and their populations boomed, spreading west, bringing them more recently into Norwegian waters. The locals have capitalized on this new species. Just in the past several years, “it has become a really important livelihood out there” in northern Norway, a place with few resources, Mykles said.
And despite this growing fishery, the crab population is still increasing. “We don’t know how this population will respond and expand in an area that is virtually wide open with no competition,” Mykles said. “It might be possible that they can adapt to even warmer temperatures and expand farther south.” Which would be good news for crabbing – but potentially bad for other interests.
The red king crab has thrived on the sandy bottoms of the Barents Sea, eating clams, worms and other bottom-dwelling creatures. But its effect on the native ecosystem remains poorly understood.
Its impact on area cod fisheries, however, has been well documented. And it’s not good – especially with cod reeling in more than $807 million for the country last year. As the crabs move west, they encroach more and more on these lucrative cod catches.
Of course, a bottom-dwelling decapod shouldn’t be much trouble for bringing in open-water fish. But the red king crab has a curious habit. In its juvenile phase, thousands of these crabs will assemble, mounding on top of one another in different locations each day. This behavior creates dense towers of crabs that can be several feet high. A hard, unexpected, 12-foot mound covered in spines and claws can wreak havoc on fishing nets. So it will be important to know just how far these crabs might expand – and into what cod-filled waters.
Ambient temperature is a key factor in the crab’s habitat size, growth – and its molting cycle. But researchers and fishery experts know little about the details of how this all comes together on a physiological level, which is where Mykles’ research comes in.
Warmer temperatures means faster growth. And when crabs outgrow their hard carapaces, they molt and grow a new one. To do this, they temporarily lose muscle tone, allowing them to wriggle out of their old shells. Once they are out – and before their new shell hardens – they furiously pump the new armor full of sea water, expanding it to provide room to grow into.
The best-quality crabs for the market are those between molts. “If you sell an animal that has just molted, you’re just selling a lot of seawater,” Mykles said. Sell them just pre-molt, and the meat quality suffers.
This temperature-paced molting is controlled by genes in the crabs’ eyestalks and molting glands. When the genes in the molting glands are expressed, molting begins – when those in the eyestalks are activated, molting is suppressed. So in addition to finding out how far this species might spread, the new research also aims to fine-tune the control of molting through these physiological and genetic channels. Being able to capture crabs and control their molting cycle before selling them would mean more year-round exports. After all, as Mykles noted, “the Arctic is not all that conducive to fishing in the winter.”
Earlier this month, during a trip to Tromsø, Norway, Mykles and a former CSU postdoc trained local scientific collaborators on dissection and tissue collection for the red king crab. The samples will be analyzed in Oslo, and then the raw data will make landfall in Fort Collins for Mykles and his team to analyze. They will use transcriptomics to sequence every gene being expressed – and look for patterns of expression at different temperatures to find clues about these crabs’ tolerance and growth.
Of course, the red king crab is a far different animal from the small land crabs Mykles has in his own lab in the Biology Building. Working with such a large crustacean, he said, “was quite an experience. They’re pretty amazing.”
He is also excited to work on such an unexpected application of his research. “My work over the last four decades has been pretty basic in understanding molting physiology, so it’s kind of cool this basic research is now having an impact – and in a place I never thought I would go.”
The project is a one-year pilot program run by Nofima, a government-supported institute that conducts research on fisheries, aquaculture and food, to gather preliminary data. The project is led by Øivind Andersen, a senior scientist at Nofima.