Intra-Seasonal Variability Of Sea Surface Temperature Influences Phenological Decoupling In Anchovy (Engraulis Ringens)

Changes in phenology are an ecological response to climate changes, in addition to other factors that may stress or dampen phenological responses. For this study, we investigated how climate variability can affect the phenology of the reproductive process of the anchovy Engraulis ringens. We used 29 years of sea surface temperature (SST) data and biological information from northern Chile stock, particularly, gonadosomatic index (GI), body condition (K), and mean weight (MTW) between 1988 and 2017. The Breaks for Additive Season and Trend (BFAST) method was applied to SST to estimate seasonal breaks and to correlate them with the seasonality of the GI. Seasonality and trend were extracted from the series to evaluate them as co-variables in GAM and GLM models in the explanation of the GI variability. The GAM model explained 56% of the variance, because it rescues the nonlinear relationships of the variables. The seasonality of the temperature explained 40%, followed by the body condition of the fish (10%). BFAST results indicate a seasonal change in SST, recording three periods: prior to 1993, 1994–1998 and after 2009. This seasonal change in the SST determines a delay in the start and the maximum in the GI. The K presented a negative relationship such as the MTW, associated with energy expenditure during the reproductive period. Faced with projections of climate change, the effects of the decoupling between larvae and the abundance during spring are not known; therefore, knowing the mechanisms that control phenology can improve our capacity to monitor and manage marine resources under climate change.