Unlike albinism, leucism is caused by a reduction in all types of skin pigment, not just melanin.
"A further difference between albinism and leucism is in eye colour. Due to the lack of melanin production in both the retinal pigmented epithelium (RPE) and iris, albinos typically have red eyes due to the underlying blood vessels showing through. In contrast, most leucistic animals have normally coloured eyes."
Both organizations also agree that this is the first time such an awesomely rare creature has been caught on camera. The photos were taken by the crew of the Spanish Fly, a fishing boat chartered through Maverick Yachts and Sportfishing Charters.