Short-term variations in the early life history traits of common sardine Strangomera bentincki and anchoveta Engraulis ringens off central Chile

A comparison of the early life history traits of two small pelagic fish species occurring in nearshore waters of central Chile was carried out based on the analysis of sagittal otolith microstructure. Plankton samples were collected in a shallow embayment at weekly scale, during six nights of austral spring 2015. Mixed schools of larval common sardine Strangomera benticki and anchoveta Engraulis ringens were studied, where the former was two to three-times more abundant than the latter. Anchoveta larvae grew faster (0.738 mm day⁻¹) than larval sardine (0.639 mm day⁻¹) but hatched at smaller size (2.62 vs. 4.85 mm, respectively); larval mortality rates was higher for sardines than anchovetas (Z_Sb = -0.164 day⁻¹; Z_Er = -0.136 day⁻¹). Back-calculated hatch dates indicate that both species were temporally coupled, excepting during early November 2015, when a large hatch event of anchoveta occurred. Both species showed similar growth trajectories during early ontogeny; however, the residuals of the micro-increment width in sagittal otoliths were negatively correlated between species. A regional warming event (SST > 15 °C) of coastal waters during late October 2015, negatively affected the recent growth rates of larval anchoveta, but not for sardines. Therefore, during spring, larvae of small epipelagic species display different responses to the same environmental forcing in the nearshore.