Validation of the AMM-based and GMM-based HSI models.

<p>The spatial distribution of the frequency of fishing effort for <i>Ommastrephes bartramii</i> in 2010 overlaid on the HSI maps generated from AMM-based model and GMM-based model during July to November.</p

The predicted HSI values for <i>Ommastrephes bartramii</i> by the AMM model.

<p>Based on the AMM-based model, the HSI value is averaged during July to November in 1998, 2008 and 2009, respectively, on the traditional fishing ground.</p

Comparing the performance of arithmetic mean model (AMM) and geometric mean model (GMM).

<p>The histogram donates the frequency of fishing effort in each HSI stratum estimated from AMM-based and GMM-based models. The solid line donates the catch per unit effort (CPUE) in each HSI stratum estimated from AMM-based and GMM-based models.</p

The frequency of fishing effort on each environmental variable and estimated SI curve for each environmental variable on the traditional fishing ground of <i>Ommastrephes bartramii</i> during July to November in the Northwest Pacific.

<p>The interaction between the SI curve and the dashed line donates the optimal range of each environmental variable (SI = 0.6).</p

Comparing the different habitat levels during 1998, 2008 and 2009.

<p>The percentage of (a) unfavorable habitat area; and (b) suitable habitat area accounting for the traditional fishing ground of <i>Ommastrephes bartramii</i> in the Northwest Pacific in 1998, 2008 and 2009, respectively.</p

Monthly average environmental variables on the fishing ground of <i>Ommastrephes bartramii</i>.

<p>Monthly average (a) SST; (b) Chl-a concentration; (c) SSHA; and (d) SSS during July to November in 1998, 2008 and 2009, respectively.</p

Comparison of the latitudinal gravity center of fishing effort, average latitude of suitable area and CPUE for each fishing month in 1998, 2008 and 2009.

<p>Comparison of the latitudinal gravity center of fishing effort, average latitude of suitable area and CPUE for each fishing month in 1998, 2008 and 2009.</p

The migration pattern of winter-spring cohort of <i>Ommastrephes bartramii</i>.

<p>The brown and yellow areas show the spawning and feeding grounds, respectively, in the North Pacific. The red area is the traditional fishing ground for the Chinese squid-jigging vessels in the Northwest Pacific Ocean.</p

Schematic diagram to show the procedure of developing habitat suitability index (HSI) model for <i>Ommastrephes bartramii</i> in the Northwest Pacific.

<p>The HSI model contains four environmental variables, including sea surface temperature (SST), sea surface height anomaly (SSHA), sea surface salinity (SSS) and chlorophyll-a (Chl-a) concentration, respectively.</p

Time series of sea surface temperature anomaly (SSTA) in the Niño 3.4 region.

<p>Results indicate that a La Niña event, average environmental condition and an El Niño event corresponded to the fishing season in the years of 1998, 2008 and 2009, respectively.</p