Leucism is rare in fish, though scientists don’t know exactly how rare it is in wild populations. Renfro’s recent catch isn’t the first time a leucistic sailfish has been caught off the sailfish-rich waters off of Guatemala. In 2018, a German fly fisherman caught a leucistic sailfish there. That specimen had a mostly black sail, while Renfro’s fish, which wasn’t fully removed from the water, had a pale one.
The sailfish has leucism, a rare genetic disorder that results in reduced pigmentation in various species of animals. The disorder is similar to but distinct from albinism, which results from the total lack of pigmentation.
Leucistic Sailfish Caught in Guatemala
News to me that billfish could be leucistic.
Also related. Marlin use rapid color changes to coordinate attacks