Bathymetric Distribution of Chaetognaths- — AlvARINO 
73 
TOTAL NUMBER OF INDIVIDUALS PER M 3 WATER FILTERED 
FIG. 5. Quantitative distribution in depth of chaetognaths in the Transpac Stations 44-54. Sta. 44, 53° 
40.8' N, 161° 55.5' E; Sta. 46, 51° 13.0' N, 164° 34.3' E; Sta. 47, 49° 50.1' N, 165° 49.2' E; Sta. 49, 47° 
35.7' N, 167° 44.8' E; Sta. 54, 40° 34.5' N, 170° 02.3' E. 
Figure 5 is a quantitative profile of the dis- 
tribution of the chaetognaths in the northwest 
Pacific, off the Kurile Trench. This diagram 
shows that the number of specimens, mainly of 
E. hamata (see also Fig. 4) is highest at about 
200-300 m. The pattern formed at stations 52 
and 54 (Fig. 6) is probably due to the turbulence 
and piling up of the central Pacific waters 
against the northern waters. At stations 52 and 
54 (Fig. 6) eight species of chaetognaths were 
observed in the upper 200 m, six were ob- 
served from 510 m to 200 m, and four species 
below 510 m; whereas at stations 44-50 S. 
elegans and E . hamata were the only chaetog- 
naths recorded in the upper 200 m and the 
latter in the strata below these levels. At stations 
52 and 54 in the upper 200 m converge S. 
elegans (arctic-subarctic); S. scrippsae (transi- 
tion ) ; S. minima , S. hexaptera, P. draco , K. sub- 
tilis ( central Pacific ) , and S. bedoti ( typical in 
those longitudes of Kuroshio waters). Between 
510 m and 300 m 5'. scrippsae, S. minima and 
K. subtilis are still found, with S. decipiens, 
S. zetesios and E. hamata. Below 510 m occur 
S. decipiens, S. zetesios, 5. macrocephala and 
E. hamata. In these stations (52 and 54) more 
species are found in the upper 200 m and mid- 
levels than in the deep layers. 
The southern boundary of S. elegans ’ distri- 
bution in the eastern Pacific and the northern 
boundary of S. scrippsae overlap (Fig. 7). S. 
scrippsae, an epiplanktonic and typical chaetog- 
nath of the Transition Area (between central Pa- 
cific and subarctic waters), the Alaska gyral, and 
the California Current ( Alvarino, 1962, in press 
a), modifies its distribution in depth with the 
geographical region and with the age of the 
individuals. S. scrippsae extends along the upper 
200 m in its main distributional region; but 
in the southernmost boundaries of the Cali- 
fornia Current, where these waters meet the 
warm inflow from the south and southwest, the 
population of S. scrippsae sinks with the cold 
waters (Fig. 8), reaching to a depth of 600 m 
in the outermost edges of the distributional 
region. This means that, although S. scrippsae 
