Initial Discoveries of Fish Faunas on Seamounts and Offshore 
Banks in the Eastern Pacific^ 
Carl L. Hubbs^ 
The recent discovery in the Pacific Ocean 
of numerous submerged mountains (Hess, 
1946; Menard and Dietz, 1951; Menard, 
1955 , and in press), including ”banks” (rising 
to a depth of less than 100 fathoms) as well 
as the flat-topped "guyots” and other '’sea- 
mounts” (with minimum depths greater than 
100 fathoms), has posed intriguing questions 
regarding their faunas. Some of these ques- 
tions are: 
What species inhabit the individual banks 
and seamounts, and in what regularity and 
abundance.^ 
How did these species become dispersed to 
and established on these structures? 
What bearing may the determined consti- 
tution of these isolated faunas have on our 
ideas concerning past and present oceanic 
circulation and temperatures? 
Do the banks and seamounts (as well as the 
islands) provide stepping stones for the 
transgression of narrow to broad oceanic 
areas, even the supposedly vast eastern Pa- 
cific barrier that separates the Indo-Pacific and 
American faunas (Ekman, 1953: 21, 72, 292)? 
May some elements in the faunas of the 
deeper seamounts be relicts that have become 
adapted to increasing depths as the seamounts 
have subsided (or become flooded)? If so, 
the faunistic evidence may have some bearing 
on the historical interpretation of the sea- 
mounts. 
To what degree has isolation on the banks 
and seamounts led to speciation? 
Are either demersal or pelagic fishes (or 
other animals) sufficiently abundant and 
^ Contributions from the Scripps Institution of 
Oceanography. Manuscript received April 10, 1958. 
2 University of California, La Jolla. 
available on or over these isolated rises to 
yield profitable fisheries? 
What factors, physico-chemical or biotic, 
are responsible for the abundance of life on 
and over these rises? The first thought that 
comes to mind is that the elevations in the 
bottom contour induce disturbances in the 
deep currents, which no doubt have greater 
velocities than they were long thought to 
have, and that such disturbances induce up- 
welling and the enrichment of the upper 
waters. 
Systematic explorations of the faunas on 
the isolated banks and seamounts (and oce- 
anic islands) should yield rich returns, both 
scientifically and commercially. As yet only 
fragmentary information has been accumu- 
lated. Some such fragments of data, recently 
acquired, concerning the fish faunas on sea- 
mounts and banks from the Gulf of Alaska 
to far-off Chile, are presented here. 
Embassichthys bathybius (Gilbert) on 
Pratt Seamount 
On August 22, 1951 , an adult "deepsea 
sole” 242 mm. in standard length surprisingly 
was caught in a rock dredge being hauled at 
a depth of 510 fathoms on the side slope of 
Pratt Seamount in the Gulf of Alaska, at Eat. 
56° 20' N., Long. 142° 30' W., about 210 
nautical miles offshore. It was obtained by 
Henry W. Menard and John D. Isaacs on the 
research ship "Horizon,” on the Northern 
Holiday Expedition of the Scripps Institution 
of Oceanography (Dredge No. 5; Collection 
SIO 53-187). 
This record constitutes a notable north- 
ward as well as seaward extension of the range 
of this deep-water pleuronectid. Long known 
311 
