Influence of environmental drivers on the interannual variability of somatic growth of the southern blue whiting (Micromesistius australis) in the Southeastern Pacific Ocean

Somatic growth in ectothermic vertebrates is an important indicator of population health. This study aimed to identify the influence of environmental drivers on the interannual variability of growth chronologies using linear mixed-effects models (LMM), for the Southern blue whiting (Micromesistius australis), a demersal fish of commercial importance in the Southeastern Pacific Ocean (SPO). Three separate growth chronologies were built based on a global (i.e., annuli), translucent and opaque band width of sagittal otoliths, over a 36-year period (1984–2019). A regime shift analysis (STARS) detected significant changes for the global growth chronology in 1993 and 1998, for the annual width of opaque zones in 1999 and for the annual width of translucent zones in 2013. LMMs showed that age was the main intrinsic factor affecting growth variability. However, extrinsic factors, such as the Pacific Decadal Oscillation (PDO), the El Niño-Southern Oscillation (ENSO) phenomenon, and sea surface temperature (SST), significantly influenced the seasonal growth of opaque bands. PDO had a negative effect on growth variability, while spring SST showed a positive correlation with opaque growth. ENSO negatively impacted seasonal growth, probably due to warming anomalies. A positive relationship was also found between chlorophyll-a concentration and growth. No relationship was observed between annual width of translucent zones and environmental drivers. The present study established the first standardized annual seasonal growth chronologies for M. australis in the SPO, identifying temperature as the main extrinsic driver triggering interannual somatic growth variation.