2 
Fishery Bulletin 108(1) 
60°N 
Sea of 
m, -i Okhotsk 
50°N 
40° N - 
30°N- 
2q°n _| winter-spring 
1 I 1 1 1 1 1 1 1 1 T 
140°E 150°E 160°E 170°E 180° 170°W 160°W 150°W 140°W 130°W 120°W 
Figure 1 
Migration pattern of the winter-spring cohort of neon flying squid ( Ommastreplies 
bartramii) in the North Pacific Ocean (Ichii et al., 2006). 
migration in October and November (Fig. 1; Ichii et al., 
2006). For a short-lived, single year-class population 
and opportunist species, the biophysical environment 
plays an important role in controlling the distribution 
and abundance of O. bartramii (Chen, 2004; Wang and 
Chen, 2005). 
Many studies have shown that environmental vari- 
ables such as sea surface temperature (SST), sea sur- 
face salinity (SSS), sea surface height anomaly (SSHA), 
chlorophyll-a (chl-a) concentrations, and current can 
strongly influence the distribution and availability of 
neon flying squid to fisheries (Chen, 1997; Chen and 
Chiu, 1999; Wang et al., 2003; Chen and Tian, 2005; 
Tian, 2006; Chen et al., 2007). Chen (1997) reported 
that monthly preferred SSTs for this squid species 
varied with seasons and areas, and the monthly pre- 
ferred SST tended to decrease gradually from west 
to east. In the waters between 150°-165°E longitude, 
the monthly favorable SSTs were 12-14°C, 14-17°C, 
15-19°C, 14-18°C, 10-13°C, and 12-15°C, respective- 
ly, for the months of June to November (Chen, 1997; 
Chen and Tian, 2005; Tian, 2006). While in the waters 
of 165-180°E longitude, the favorable SST in June 
and July ranged from 11-15°C (Chen and Tian, 2005; 
Tian, 2006). Yatsu and Watanabe (1996) reported that 
catch per unit of effort (CPUE) for the driftnet fishery 
near the Subarctic boundary in July was highest dur- 
ing years with a strong gradient between the 11 and 
15°C SST isotherms. Chen and Chiu (1999) found that 
the distribution and abundance of O. bartramii in the 
central North Pacific Ocean were strongly influenced 
by water temperature and salinity, with temperature 
having a higher predictive power for estimating stock 
abundance. Tian (2006) reported that the monthly 
favorable SSSs for squid were 33.8-34.3, 33.3-34.4, 
33.0-34.2, 33.0-33.7, 33.0-33.8 and 33.3-33.8 from 
June to November, respectively, in the north Pacific. 
Chen et al. (2007) discussed the influence of large-scale 
oceanic phenomena such as the Kuroshio Extension 
and El Nino Southern Oscillation (ENSO) events on 
squid distribution and recruitment. They concluded 
that these phenomena influence squid by affecting the 
SST and SSS of the spawning and feeding grounds. 
From July to November, O. bartramii migrate north 
to feed. The presence of plankton also is a basic neces- 
sity for the presence of this squid (Chen, 2004). Wang 
et al. (2003) reported that a skewed distribution func- 
tion could be used to describe the relationship between 
chlorophyll-a concentration and O. bartramii catch 
in the waters of 150-165°E longitude and 41-45°N 
latitude from August to October, and that the area 
with chlorophyll-a content ranging from 0.15 to 3 mg/ 
m 3 produced 95% of the total catch. Xu et al. (2004) 
found that in the waters of 152°E-171°W longitude and 
39°-42°N latitude during June and July, O. bartra- 
mii tended to aggregate near areas with the highest 
abundance (50-100 ind/m 3 ) of crustaceans (mainly 
Copepoda and Thaliacea). 
Sea surface height anomaly (SSHA) is an important 
marine environmental variable that is closely related 
to the distributions of some fish species (Zhang et al., 
2001) and is also considered an important environ- 
mental indicator for finding fishing grounds (Chen, 
2004). Tian (2006) reported that O. bartramii is mainly 
distributed in the areas where the value of SSHA is 
below or near zero from August to November. Lu and 
Chen (2008) found that the squid Illex argentinus pre- 
ferred habitats with zero or negative values of SSHA 
in the southwest Atlantic Ocean. This phenomenon 
also existed in the study of habitat suitability for chub 
