Grampus griseus
Risso's are the most heavily scarred marine mammal on the planet — adults accumulate thousands of crisscross marks from the beaks and suckers of the Humboldt squid they hunt at depths beyond 1,000 feet, fading the skin from charcoal grey to near-white with age. Look for groups of 10–50 logging quietly at the surface off the Channel Islands, especially on calm October and November mornings.
Risso's were seldom seen around Santa Catalina Island before the 1980s. After the 1982–83 El Niño the resident short-finned pilot whales virtually disappeared, and Risso's increased there from 1987 onward — one species vacating a niche and another moving in.
HOW RARITY IS JUDGED →Newport & Long Beach operators share daily trip counts — you can see what was spotted before you book. Other operators don't publish daily reports.