OCEAN CHRONICLES
Dall's porpoise swimming in the emerald green waters of Southeast Alaska © Josh McInnes
SPECIES IN THE SPOTLIGHT
DALL'S PORPOISE Phocoenoides dalli JOS H M C IN N E S
The sun glinted off the emerald green water
1927) during an expedition aboard the USS Nightingale
as we slowly traveled north in Frederick Sound, Alaska.
in British Columbia, Alaska, and the Russian Far East
We were on our final day of a weeklong marine mam-
in 1865-1867. His distinct notes on the species mor-
mal survey aboard the motor vessel David B, in the
phology, and the collection of a specimen, allowed his
heart of Southeast Alaska. Up ahead a group of seven
colleague Frederick W. True to classify it as a distinct
Dall’s porpoise charged head on towards our vessel, a
species, which was subsequently named after him. The
v-shaped spray of water called a rooster tail emanated
Dall’s porpoise is one of six species of porpoise belong-
ahead of their torpedo shaped bodies. The porpoises
ing to the family Phocoenidae. They are endemic, but
began riding the bow wave created by the David B, us-
widely distributed in offshore and coastal waters of the
ing the wave’s momentum to push their bodies steadily
cool temperate Pacific Ocean. Two sub-species known
forward. Each porpoise crisscrossed in a competitive
as Phocenoides dalli dalli and Phocenoides dalli truei
dance as they vied for each wave the vessel created.
have been distinguished based on differences in mor-
This extraordinary behaviour lasted for over an hour
phological and genetic characteristics. Phocenoides
before the Dall’s porpoises departed. An encounter
dalli dalli is primarily encountered in the Northeastern
with a group of Dall’s porpoise is truly a breathtaking
Pacific, and is distributed from the Bering Sea south to
experience, and mariners traversing the coastal waters
Southern California. It has been estimated that the total
of the Inside Passage commonly encounter these small
abundance of Dall’s porpoises in the North Pacific rang-
but playful cetaceans.
es 1 to 1.2 million. This subspecies is easily recognizable by their robust body, short-beaked head, and black
The Dall’s porpoise was first described by the American
and white coloration A similar pattern found in killer
naturalist and paleontologist William Healey Dall (1845-
whales (Orcinus orca). Their dorsal fins are rectangular
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