The jumbo flying squid Dosidicus gigas is a highly migratory species distributed throughout the Eastern Pacific Ocean. An integrated habitat suitability index (HSI) model was developed to evaluate the effects of climate variability (i.e. El Niño-Southern Oscillation) on the habitat suitability for D. gigas in the Southeast Pacific Ocean off Peru. The data used in the analysis included catch and fishing effort from the Chinese squid-jigging fishery over 2006–2013, as well as remotely sensed environmental data including sea surface temperature, chlorophyll a and sea surface height anomaly. Arithmetic mean HSI model was shown to have a better predictive performance and used to predict the HSI values and identify the suitable habitat for D. gigas over 2006–2012. Fishery and environmental data in 2013 was used to validate the model. The latitudinal location of suitable habitat was found to be important in determining the distribution of fishing efforts. Cross-correlation plot exhibited a significantly negative relationship between the average HSI values on the fishing ground and the Niño 3.4 indices with time-lags from −1 to 3 months, implying that the squid habitat responded quickly to the climate variability. Both suitable habitat areas and catches of D. gigas increased in La Niña periods and decreased in El Niño periods. The La Niña conditions tended to strengthen upwelling coupled with cool and nutrient-enhanced waters, which yielded favourable habitat conditions and high catches; whereas the El Niño conditions weakened upwelling coupled with warm and nutrient-depleted waters, which were unfavourable for squid habitat and reduced catches. Our findings indicated that large-scale climate variabilities could have great effects on squid habitat and such variabilities could be quantified by climate indices such as Oceanic Niño index.

We developed a habitat suitability index (HSI) model to evaluate the variability of suitable habitat for neon flying squid (Ommastrephes bartramii) under anomalous environments in the Northwest Pacific Ocean. Commercial fisheries data from the Chinese squid-jigging vessels on the traditional fishing ground bounded by 35°-45°N and 150°-175°E from July to November during 1998-2009 were used for analyses, as well as the environmental variables including sea surface temperature (SST), chlorophyll-a (Chl-a) concentration, sea surface height anomaly (SSHA) and sea surface salinity (SSS). Two empirical HSI models (arithmetic mean model, AMM; geometric mean model, GMM) were established according to the frequency distribution of fishing efforts. The AMM model was found to perform better than the GMM model. The AMM-based HSI model was further validated by the fishery and environmental data in 2010. The predicted HSI values in 1998 (high catch), 2008 (average catch) and 2009 (low catch) indicated that the squid habitat quality was strongly associated with the ENSO-induced variability in the oceanic conditions on the fishing ground. The La Niña events in 1998 tended to yield warm SST and favorable range of Chl-a concentration and SSHA, resulting in high-quality habitats for O. bartramii. While the fishing ground in the El Niño year of 2009 experienced anomalous cool waters and unfavorable range of Chl-a concentration and SSHA, leading to relatively low-quality squid habitats. Our findings suggest that the La Niña event in 1998 tended to result in more favorable habitats for O. bartramii in the Northwest Pacific with the gravity centers of fishing efforts falling within the defined suitable habitat and yielding high squid catch; whereas the El Niño event in 2009 yielded less favorable habitat areas with the fishing effort distribution mismatching the suitable habitat and a dramatic decline of the catch of O. bartramii. This study might provide some potentially valuable insights into exploring the relationship between the underlying squid habitat and the inter-annual environmental change.

The jumbo flying squid, Dosidicus gigas, support an important squid fishery off the Exclusive Economic Zone of Chilean waters. However, we only have limited information about their biology. In this study, age, growth and population structure of D. gigas were studied using statoliths from 533 specimens (386 females and 147 males) randomly sampled in the Chinese squid jigging surveys from 2007 to 2008 off the Exclusive Economic Zone of Chile. Mantle lengths (MLs) of the sample ranged from 206 to 702 mm, and their ages were estimated from 150 to 307 days for females and from 127 to 302 days for males. At least two spawning groups were identified, the main spawning peak tended to occur between August and November (austral spring group), and the secondary peak appeared during March to June (austral autumn group). The ML–age relationship was best modelled by a linear function for the austral spring group and a power function for the austral autumn group, and the body weight (BW)–age relationship was best described by an exponential function for both the groups. Instantaneous relative growth rates and absolute growth rates for ML and BW did not differ significantly between the two groups. The growth rate of D. gigas tended to be high at young stages, and then decreased after the sub-adult stage (>180 days old). This study suggests large spatial and temporal variability in key life history parameters of D. gigas, calling for the collection of more data with fine spatial and temporal scales to further improve our understanding of the fishery biology of D. gigas.