Shark Ecology 97
Some species occur throughout an ocean basin; this is the case with the Pa-
cific Spookfish (Rhinochimaera pacifica) in the Pacific Ocean and the Broad-
nose Chimaera (R. atlantica) in the Atlantic. The Narrownose Chimaera
(Harriotta raleighana) occurs in both the Pacific and the Atlantic. Australia
and New Zealand may have the highest diversity of chimaeras, with at least
nine species recorded from that region.
Which sharks are most or least abundant?
Probably the most abundant shark in the world is the Spiny Dogfish
(also known as the Spur Dog or Piked Dogfish), Squalus acanthias, and its
close relative, Squalus suckleyi. S. acanthias occurs off the Atlantic coasts
of the United States, Canada, and Europe, and also off southern South
America, Africa, Australia, and New Zealand. The closely related S. suck-
leyi, until recently considered the same species, inhabits the North Pacific.
Commercial landings of the latter off the west coasts of the United States
and Canada exceeded 50,000 metric tons (100 million pounds) per year
in the mid-1940s. At about 3 pounds average per fish, that is over 33 mil-
lion sharks! Some recent estimates of the abundance of the Atlantic species
off the coast of Canada run as high as 535 million sharks, and the number
off the combined Pacific coasts of Canada and the United States is put at
almost 2 billion individuals. As abundant as those numbers appear, these
(To p) A Spiny Dogfish, probably the
world’s most abundant shark, off
the coast of New England. The typi-
cal color is bronze-gray with white
spots. (Bottom) Geographic ranges,
shown in black, of the Spiny Dog-
fishes Squalus acanthias and S. suck-
leyi. The latter occupies the North
Pacific. To p, photo by Doug Costa, National
Oceanic and Atmospheric Agency, https://
marinelife.noaa.gov/media_lib/preview
.aspx?ID= 7299 &p=img; bottom, map from
http://en.wikipedia.org/wiki/File:Squalus
_acanthias_distmap.png