Syah et al.: Predicting potential fishing zones for Cololabis saira 
339 
At the beginning of the fishing season, fishing loca- 
tions derived from OLS images showed that most of 
the vessels that fished for Pacific saury appeared east 
of Hokkaido and south of the Kuril Islands (Fig. 3, A 
and B). In the middle of the fishing season (October 
to November) (Fig. 3, C and D), vessels that fish for 
Pacific saury moved slightly to the south and appeared 
mostly around the eastern coasts of Hokkaido and 
Sanriku — a finding that potentially resulted from the 
southward extension of Oyashio fronts (Watanabe et 
al., 2006; Tseng et al., 2011). At the end of the fishing 
season, vessels that fish for Pacific saury were concen- 
trated along the Sanriku coast (Fig. 3E). 
Images from the OLS also showed that some of the 
fishing vessels appeared outside the FEZ, possibly be- 
cause Pacific saury is an oceanic spawner, unlike oth- 
er small pelagic fishes, such as the Japanese sardine 
iSardinops melanostictus) and the Japanese anchovy 
[Engraulis japonicus), that generally spawn in the 
coastal and near shore waters of Japan (Zenitani et 
al., 1995). The low capture of fish west of 150°E from 
June through July before the fishing season indicates 
that Pacific saury caught by Japanese fishing vessels 
were located far from the northeastern coasts of Japan 
(Tohoku National Fisheries Research Institute^). 
The predicted distribution of Pacific saury in the 
western North Pacific revealed areas of high probabil- 
ity of occurrence off Hokkaido and the Kuril Islands 
(Fig. 6, A-F), areas that gradually moved south toward 
the Sanriku and Joban coasts by the end of the fish- 
ing season (Fig. 6, M-0). These patterns coincided with 
the north-south migration of Pacific saury that marks 
the start and end of the fishing season. Results from 
a maximum entropy approach further indicate that 
the highest probability of presence occurred along the 
Kuroshio-Oyashio transition zone in November (Fig. 6, 
J-L). 
The occurrence of large-size Pacific saury (>29.0 cm 
in knob length) off the southern Kuril Islands dur- 
ing their spawning migration indicates that a high 
proportion of large-size Pacific saury moved from the 
high seas to coastal waters at the beginning of their 
migration toward the southwest — movement that was 
then followed by a similar migration of medium-size 
Pacific saury (24.0-29.0 cm in knob length). Therefore, 
abundance of Pacific saury off the coastal waters in our 
study is higher than the abundance observed in regions 
in the high seas (Huang, 2010). In addition, the high 
density of Pacific saury off Hokkaido and the Kuril Is- 
lands was probably related to the southward movement 
of the Oyashio Current (Tseng et al., 2011). The high 
presence of Pacific saury at the coasts also could be 
a result of a westward current intensification, which 
can result in the formation of oceanic fronts (Huang, 
2010). These frontal features have been known as the 
^ Tohoku National Fisheries Research Institute. 2010. The 
58*** Annual Report of the Research Meeting on Saury Re- 
sources, 250 p. Tohoku Natl. Fisheries Res. Inst., Hachi- 
nohe, Japan. [In Japanese.] 
preferred migratory routes of Pacific saury and other 
marine species (Saitoh et al., 1986; Zainuddin et al., 
2008). 
Although oceanographic conditions are likely to af- 
fect species distribution, other factors, such as prey 
density, are equally important. In the Kuroshio-Oyas- 
hio transition zone, Oyashio intrusions transport or- 
ganic matter, thereby supporting the production of 
copepods, which are the primary prey of Pacific saury 
(Odate, 1994; Shimizu et al., 2009). This salient physi- 
cal process could potentially explain the existence of 
habitat areas of Pacific saury in the transition zone, ar- 
eas that were identified with maximum entropy models 
and that consequently highlight the importance of this 
region as migratory and feeding corridors for Pacific 
saury. 
The variability of the performance of the maximum 
entropy model was very low across the monthly base 
models, where AUCs higher than 0.9 indicate that 
models had excellent agreement with the test data 
(Table 4). As pointed out earlier, productivity and fish 
distribution are influenced by changes in the environ- 
ment evident from the variations in temperature, cur- 
rents, salinity, and wind fields (Southward et al., 1988; 
Alheit and Hagen, 1997). In our study, SST (among the 
set of oceanographic variables examined) showed the 
highest contribution to all monthly base models (Table 
5), indicating the sensitivity of Pacific saury to tem- 
perature changes. For instance, increasing SST will 
directly reduce juvenile growth and prevent, or delay, 
the southern migration of Pacific saury in winter (Ito 
et al., 2013). Moreover, changes in winter SSTs in the 
Kuroshio-Oyashio transition zone and in the Kuroshio 
and Oyashio regions also affected the abundance of the 
large-size (winter cohort) and medium-size (spring co- 
hort) groups of Pacific saury (Tian et al., 2003). 
To our knowledge, this study was the first attempt to 
use both EKE and SSHA to describe potential fishing 
habitat of Pacific saury in relation to mesoscale ocean- 
ography variability. Our results indicate that fishing 
activities occurred in areas with low to moderate EKE 
(Fig. 5), reflecting the likely association of this species 
with eddies. Meandering eddies likely trap prey of Pa- 
cific saury, creating good feeding opportunities through 
local enhancement of chl-a and zooplankton abundance 
and through the aggregation of prey organisms (Owen, 
1981; Zhang et al., 2001). The importance of forage 
availability for Pacific saury is further reflected in the 
higher contribution of chl-a concentration to the base 
model in September (Table 5). Together with SST, chl-a 
has been found to influence Pacific saury growth, re- 
cruitment, distribution, and migratory patterns (Ito et 
al., 2004; Oozeki et al., 2004; Yasuda and Watanabe, 
2007). However, from November through December, 
the distribution of Pacific saury likely is not limited 
by food availability because of a general increase in 
ocean mixing and a decrease in water column stratifi- 
cation during this period. These oceanographic condi- 
tions consequently enhance the chl-a concentration in 
the mixed-water region (Mugo et al., 2014). 
