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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]

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Abstract Habitat modeling approach is a useful tool to detect potential habitat of pelagic fish species for better fishery exploitation and management. In this study, an integrated habitat modeling approach was applied to examine seasonal habitat patterns of an ecologically and economically important squid species Dosidicus gigas in the Southeast Pacific Ocean off Peruvian waters. Fisheries data of D. gigas and three crucial remotely-sensed environmental variables including sea surface temperature (SST), net primary production (NPP) and sea surface height anomaly (SSHA) during 2006–2015 were used to develop and validate the habitat model. Results revealed that the model output robust predictions of seasonal habitat suitability for D. gigas stock. Potential habitat exhibited strong seasonal variability, characterized by an expansion of suitable habitat during spring-autumn period and an extreme reduction in winter. These seasonal habitat patterns of D. gigas were largely driven by spatial distribution of favorable environmental conditions. Spatial correlation analysis indicated that the habitat quality of D. gigas was negatively correlated with SST in the areas between 8°–15°S and 87°–79°W and with SSHA on the whole fishing ground. However, a negative relationship was found between HSI values and NPP in the east of 84°W, but with a significantly positive correlation in the west of 84°W. In addition, seasonal variations of CPUEs and latitude distribution of fishing efforts were highly coincided with the variability trends in the area of suitable habitats and their latitudinal distributions. Interannual variability was shown in the averaged HSI of D. gigas. Furthermore, comparing to the strong El Niño year in 2015, the La Niña event in 2011 yielded more enlarged favorable regions of each environmental factor in each season, leading to form extremely high-quality habitats. Highlights • A habitat model was built to examine seasonal habitats of jumbo squid off Peru. • Potential habitats of jumbo squid showed significant seasonal spatial patterns. • Environmental conditions strongly affected seasonal habitats of jumbo squid. [ABSTRACT FROM AUTHOR]

The pelagic cephalopod species jumbo flying squid Dosidicus gigas is ecologically and economically important in the Humboldt ecosystem off Peru. This squid species is sensitive to oceanic environmental changes, and regional oceanographical variability is one of the important factors driving its redistribution. Off Peruvian waters, mesoscale eddies are ubiquitous and dominate the biogeochemical processes in this region. This study first explored the role of mesoscale eddies in regulating the environments and their effects on the abundance and habitat distribution of D. gigas off Peru by analyzing squid distribution in eddy-centric coordinates and building a habitat suitability index (HSI) model. Results indicated that the abundance and habitat distribution of D. gigas in mesoscale eddies varied across months, with significant differences observed between anticyclonic eddies (AE) and cyclonic eddies (CE). In AE, a higher abundance and proportion of suitable habitat occurred. While in CE, the abundance was relatively low and the suitable habitat was relatively less, concentrating at the periphery of CE. Based on the HSI model results, sea surface temperature (SST) and 50 m water temperature (T50m) in AE were more favorable for D. gigas , which was 0.3–0.5 °C lower than that in CE, yielding high-quality habitats and higher abundance of D. gigas. Our findings emphasized that mesoscale eddies have a significant impact on water temperature conditions and nutrient concentrations off Peruvian waters. • The eddy-induced changes in Dosidicus gigas distribution were first explored. • Mesoscale eddies have impacts on water temperature and nutrient condition. • A higher abundance of D. gigas and enlarged suitable habitat occurred in anticyclonic eddies. [ABSTRACT FROM AUTHOR]