Frank McFarland found the blue crab in his pot when fishing on July 4 off Nome, KNOM reported.
The blue crab is being kept alive at the Norton Sound Seafood Centre until Mr McFarland can have it mounted.
The rare crab has become a rock star of sorts, with people showing up at the centre to have their photos taken with it.
Scott Kent, of the Alaska Department of Fish and Game in Nome, said he has no idea why the red king crab is blue, but suspects it is just a mutation.
Mr Kent said a blue crab "turns up once in a blue moon".
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