Synchronous spatio-temporal changes in potential habitats of Trachurus murphyi and Dosidicus gigas off Chile in relation to regime shift of Pacific decadal oscillation

Understanding concurrent responses of habitat pattern of pelagic fish species to climate variability is favorable for sustainable exploitation and fisheries management. In this study, the key environmental factors affecting Dosidicus gigas (sea surface salinity (SSS), sea surface height anomaly (SSHA) and water temperature at 400 m (Temp_400m), and Trachurus murphyi (sea surface temperature (SST), mixed layer depth (MLD) and Temp_400m), were used in combination with the Pacific Decadal Oscillation (PDO) index to examine synchronous habitat variations off Chile based on habitat suitability index model (HSI). All environmental factors were significantly related to the PDO. A significantly negative relationship was found between the HSI of D.gigas and the PDO index, while a significantly positive correlation was observed in the HSI of T.murphyi. In the warm PDO regime, MLD was shallower, SST increased, and SSHA decreased from the northeast to the southwest off Chile. SSS and Temp_400m in northern waters off Chile were higher than those in southern waters. The suitable habitats of D.gigas contracted and shifted southwestward. While the area and distribution of T.murphyi changed little, but its habitat quality enhanced. In the cold PDO regime, SST and SSHA decreased, and MLD deepened. Variations in SSS and Temp_400m were consistent with those in the warm PDO regime. The suitable habitats of D.gigas enlarged and moved northeastward. Whereas the suitable habitats of T.murphyi slightly reduced with small change occurred with its spatial location. Our findings suggested that the PDO played important roles in the long-term concurrent habitat variations of Chilean T.murphyi and D.gigas.