414 
superficial waters are warmer and lives in shal- 
lower water when these waters are colder, ap- 
parently seeking out temperatures in the 4°C 
isotherm region. 
Gnathophausia gracilis 
This species, by contrast, is confined to a 
small latitudinal range between 35°N and 20°S 
(Fig. 10). Previously only four captures had 
been made outside the tropical zone (i.e., 23°N 
to 23°S), these being taken from the Atlantic 
Ocean. None had been taken north of the 
Tropic of Cancer in the Pacific. However, of 
the 128 individuals of G. gracilis in the Scripps 
collections, a total of 99 specimens were found 
from stations north of the Tropic of Cancer. A 
great majority of the larger individuals (greater 
than 80 mm body length) came from north of 
the Tropic of Cancer, and all of the largest in- 
PACIFIC SCIENCE, Vol XIX, October 1965 
dividuals of greater than 100 mm body length 
came from north of 23°N, the maximum lati- 
tude of occurrence being 33 °N. However, com- 
pared with the other species of Gnathophausia , 
G. gracilis was the most conspicuous species in 
the Scripps hauls from the tropical regions of 
the eastern Pacific, with no G. gigas and only a 
few G. ingens occurring in collections taken 
south of the Tropic of Cancer. 
Fage (1941) reports that the G. gracilis 
found in the Pacific (especially in the eastern 
Pacific where, in the Gulf of Panama, the 
adults captured by the Dana did not exceed 65 
mm length ) are of smaller size than those of 
the Atlantic. His largest specimens (2 males 
and 1 female, each 100 mm in length) came 
from the Atlantic in the vicinity of the Carib- 
bean Sea, and he believes that sexual maturity 
is more precocious in the specimens from the 
Pacific, particularly in the eastern Pacific, where 
Fig. 9- Geographical Distribution of Gnathophausia gigas. Solid circle, captures of the Dana Expedition; 
plus sign, other previous captures; solid triangle, captures from the 1950-53 Scripps collections. 
