First measurements of euphausiid growth rates in the northern Humboldt Current (23ºS)

Abstract

One hundred and five juveniles and adults of Euphausia mucronata were incubated in order to estimate their daily growth rates (DGR) using the standard instantaneous growth rate method. From 77 krill that survived after 2 days of incubation under laboratory conditions, 70 individuals molted (35.1% males, 64.9% females). E. mucronata mean intermolt period was 5.2 days (range = 4-9 d) with mean DGR of 0.01 mm d-1 for males and -0.04 mm d-1 for females. Overall mean DGR was -0.02 mm d-1. DGRs were positive (31%), zero (12%) and negative (57%). DGR<0 evidenced body shrinking process suggesting that environmental conditions in austral autumn 2010 were unfavorable for the krill population. However, because females had DGR<0 values more frequently than males it is probable that females also used part of their energy on gonad development rather than body growth.