Mackerel icefish generally become less active and more benthic as they age. Larvae and juveniles are pelagic, active predators of krill. There is some evidence they become more sedentary as they age.

There is no evidence of nesting or guarding a nest in C. gunnari. They reproduce by spawning during 2-3 months of the fall, directly before which they move inshore. (Kock 2005a)