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In this study, the four most important species in the Humboldt Current System (HCS), Engraulis ringens, Sardinops sagax, Trachurus murphyi, and Dosidicus gigas were linked to four climate indices, sea surface temperature (SST) and wind speed (WS) based on multivariate statistical analyses, aiming to explore their nonstationary responses to climate variability. Significant decadal variations in the catches were identified, with regime shifts in the mid-1970s, early 1990s, and late 1990s. These shifts corresponded well to climatic and environment regime shifts during these periods. However, the response patterns to climate and environmental variations varied among species. Compared with other physical drivers, seawater temperature, wind speed, the Pacific Decadal Oscillation (PDO), and the North Pacific Gyre Oscillation (NPGO) had greater ecological importance in driving changes in the four pelagic species. The variations in the important climate events influenced seawater temperature and wind speed fluctuations within the HCS, impacting on these commercially important pelagic species. Furthermore, non-stationarity was identified in the relationships between climate/environment and species catches, with different species showing different threshold years. The non-stationarity may be attributed to the transitions between warm and cold periods within the HCS, as well as shifts between strong and weak phases of pressure system. This study helps further understand changes in the HCS caused by fluctuations in climate and environment. [ABSTRACT FROM AUTHOR]

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 21 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. [ABSTRACT FROM AUTHOR]