Blue whale in Los Cabos

How to recognize it

Enormous, long and slender, mottled blue-gray (light blue underwater). The head is broad and U-shaped seen from above, and the dorsal fin is tiny (about 30 cm) and set three-quarters of the way back, so it appears only at the end of a long roll of the back. The blow is a single thick column 6 to 12 m high. It usually doesn’t lift its tail, except sometimes on the last dive of a sequence.

Biology

Eastern North Pacific blue whales feed off the U.S. West Coast in summer and fall, and most migrate south for winter and spring to productive waters off Baja California, in the Gulf of California and on the Costa Rica Dome. Mexico’s whale-watching standard (NOM-131) describes an important nursery area between Bahía de La Paz and Loreto. The last mark-recapture estimate for this population was 1,647 whales (2008–2011).

It feeds almost only on krill: it swims into a swarm with its mouth open, inflates its pleated throat, then pushes the water out through its baleen, and the biggest individuals can eat up to 6 tons a day. Pregnancy lasts 10 to 12 months; the calf is born about 7 m long and weighing 2.5 to 4 tons, is weaned at 6 to 7 months, and females calve every 2 to 3 years. North Pacific blue whales reach about 27 m; the Antarctic ones are larger, and the biggest on record measured 33 m.

Seeing them from the boat

Off Los Cabos, blue whales turn up only now and then, from about December to April: recent sighting records average roughly one encounter a year, and Gordo Banks fishing reports from 2010–2026 never mention one. Most are seen farther up the Gulf, in Loreto Bay National Park, where the season runs from about January–February to late March or early April. Off Cabo, a blue whale on an offshore trip is a lucky sighting, not something anyone can promise.

If we find one, we slow down, bring the lines in and watch from a distance: Mexican rules give blue and fin whales a bigger buffer than humpbacks or gray whales, and boats watching whales may not use sonar or a fishfinder to locate them or trail lines or hooks. A long roll of the back, then a tiny fin at the very end, is usually all you’ll see, and a thick blow that can rise over 6 m.

Rules & conservation

Don't confuse it with

The fin whale is almost as long but slimmer and darker gray, its dorsal fin is taller and appears soon after the blow, and its lower jaw is white on the right side only. Blue whales have all-black baleen and a broad, U-shaped head.

Questions

By Max VargasTop Anglers, Cabo San Lucas · international judge at big game fishing world championships · reviewed October 2026

Sources

• NOAA Fisheries: blue whale
• NOAA stock assessment: blue whale, eastern North Pacific (2019)
• Whittome et al. 2024, blue whales in the Gulf of California (Marine Mammal Science)
• Bailey et al. 2009, satellite tracks of blue whales (Endangered Species Research)
• IUCN Marine Mammal Protected Areas Task Force: Costa Rica Thermal Dome
• Rice et al. 2022, blue whale call frequency decline (PLOS ONE)
• Phys.org: first blue whale heart rate (Goldbogen et al. 2019, PNAS)
• International Whaling Commission: blue whale
• NOM-131-SEMARNAT-2010 (PROFEPA)

Top illustration: Top Anglers. Photos: iNaturalist contributors, credited on each photo.