Growth of the Humboldt Current krill in the upwelling zone off central Chile

Temporal variability in the daily growth rate (DGR) of the Humboldt Current krill, Euphausia mucronata, was studied in eighteen incubation experiments off the coast of Dichato, central Chile (36.5 degrees S), carried out in 2011-2014. Intermolt period (IMP) was derived from the molting rate method in order to estimate the DGRs. Mean IMP was 9.2 +/- 4.8 days (range: 2.9-18.7 d). Overall mean DGR was 0.03 +/- 0.13 mm d(-1). DGR showed a dome-shaped pattern, with a higher mean DGR when upwelling was moderate (0.06 +/- 0.04 mm d(-1)) than intense (0.01 +/- 0.00 mm d(-1)) or weak (0.01 +/- 0.01 mm d(-1)). This dome-shaped trend was observed in chlorophyll-a concentrations (Chla) at similar upwelling regimens. E. mucronata DGR variability was best explained by a generalized linear model which included the contribution of the Equatorial Subsurface Water, temperature, dissolved oxygen and Chla as predictor variables. Results suggest that E. mucronata is better adapted to grow under upwelling conditions when it can take advantage of high biological productivity, although the species growth is not limited when weak upwelling or even downwelling occurs. Analysis of the duration of the upwelling events suggest that E. mucronata growth is limited (shrinking) when upwellings last >10 days. (C) 2016 Elsevier B.V. All rights reserved.