Whale Alert – West Coast

Whale Alert – West Coast

Minke whale

Balaenoptera acutorostrata 

The minke whale is the smallest baleen whale in the California Current, less than half the size of the fin and sei whales.  They are designed for speed and can be very acrobatic, sometimes observed leaping completely out of the water.

Conservation status

Appearance

As the smallest baleen whale in the California Current, the minke whale only reaches a maximum length of 10 m (33 feet) and a weight of up to 10,000 kg (4 to 5 tons).  It has a slender profile with a narrow, pointed head and short, trim flippers.  A single distinct ridge runs from the blowhole guard toward the snout and its mouth gape is limited with only 50 to 70 short throat pleats.  The dorsal fin is pronounced, semi-circular in shape, and extends about two-thirds down its back, making it easy to spot when it surfaces or dives.  Its coloration is black to dark gray on its back while the undersides are white.  They often have lighter, chevron patches across the back behind the head.  However, the most distinctive color pattern is a white or light gray band across the fore-flippers which can easily be seen above and below the surface of the water.

Distribution and migration

Minke whales are found throughout most of the oceans of the world, and three subspecies can be found in the Northern Hemisphere.  The northern Pacific subspecies can further be separated into five separate stocks, one of which is associated with the California Current.  This California Current stock is likely separated into small, isolated, non-migratory populations.  However, another stock (Alaskan) is also found in the California Current during migration as it travels south nearly to the equator from the Chukchi Sea in the north.  Year-round presence has been noted the San Juan Islands, in Washington to British Columbia, and in Drakes and Monterey Bays in California.  Migration is not as long as that of the gray whale, and no distinct calving grounds have been identified.  Howerver, calving may occur in temperate waters along the coast, as newborn calves have been found washed ashore in places along the coast, including Drakes Bay in central California.

Habitat

Throughout its range, the minke whale is associated with areas of consistent upwelling, high primary productivity, and where the seabed sediments are gravelly sand or mud.  They are also found along and on the continental shelf and around islands, reefs, and seamounts.  Inshore, they are present in bays and estuaries as well as large river mouths along the periphery of kelp beds.  They most often occur within 160 km (100 miles) from shore and usually within just 20 km (12 miles).  Although they are relatively close to shore, the best way to see them is by boat.  They can be curious and will often approach vessels, providing easy viewing.

Feeding style and diet

The diet of the minke whale is diverse, as they feed on what is seasonally and locally abundant.  Prey includes a variety of fish like small, schooling, bait-type fish such as herring, sardines, anchovies, sand lance, saury, sand eel, salmon, hake, mackerel, and smelt.  They also eat invertebrates including squid, krill, copepods, pteropods, and mysid shrimp.  With its small and sleek body, the minke whale is effective in chasing down schools of fish and will lunge while pursing fish, then gulp their catch.  However, they are also efficient at catching prey on the surface of the water as well as the ocean floor.

Other common species found on the west coast

Blue whale     Fin whale     Humpback whale     Gray whale     Killer whale

Learn more

Want to learn more about whales along the west coast? 
Check out the Field Guide to MARINE MAMMALS of the Pacific Coast, a California Natural History Guide by Sarah G. Allen, Joe Mortenson, and Sophie Webb.