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New Studies Raise Questions About Crabs Adaptability

Tanner and blue king crab stocks in Alaska waters uncertain


Juvenile blue king crab.

Photo courtesy NOAA Fisheries

Sixty percent of U.S. seafood comes from Alaska. A profitable portion of this comes from the famed crab fisheries. New studies on the effects of ocean acidification due to rising atmospheric carbon dioxide levels support a growing body of evidence that the future for Tanner and blue king crab stocks in Alaska waters is, at best, uncertain.




In a separate study on blue king crabs, scientists also saw slower growth rates and higher mortality in juveniles exposed to more acidic conditions. Blue king crabs have supported an important fishery in the Bering Sea.  However, their populations around the Pribilof Islands and St. Matthew Island regions have fluctuated dramatically. This suggests that environmental conditions play a big role in the number of young crabs that actually grow to maturity and can be caught by the commercial fishery.  Changes in ocean acidification may make it even more difficult for these populations to recover from recent low levels.



(ABOVE) Blue king crab eyed embryos; the large black patch is the eye; yellow region is yolk; red splotches are chromatophores (color cells).

(BELOW) Blue king crab larva right after hatching.

Photos by Bradley Stevens, NOAA Fisheries




University of Washington scientist André Punt used these projections to evaluate effects on the lucrative commercial fisheries that rely on these crab species for their livelihoods. 

“Our projections suggest that unless crab adapt to changing pH, we will be seeing lower catches in 40-50 years and the need for more effort to catch the crab that are out there,” said Punt.

So the big unanswered question is then if the change in pH over decades is gradual, can crabs adapt?


An adult Tanner crab. Photo credit: NOAA Fisheries


March 1, 2016


“If there are any bright spots in all of this, it is that we saw evidence that both Tanner and blue king crab species have the capacity to adapt,” said Foy.

For Tanner crabs, even at the lowest pH tested, pH 7.5, some larvae, embryos and juveniles survived and grew, indicating variability in individual tolerances for low pH and the potential for natural selection to allow adaptation to acidified conditions. 

“For blue king crabs, we saw  over the course of our year-long study that juveniles became more tolerant of more acidic conditions the longer they were exposed. The longer they were in acidified conditions, the less likely they were to die,” said Long.  “This suggests that they are able to alter their body chemistry to adapt to acidified conditions. Their ability to adapt will really depend on how fast pH conditions change.”



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