Daily growth patterns and age-at-recruitment of the anchoveta Engraulis ringens as indicated by a multi-annual analysis of otolith microstructure across developmental stages

The anchoveta (Engraulis ringens) plays a key role in the ecology of the Humboldt Current System and is of major economic importance; however, many aspects of its early life history are still poorly understood. In this study, an analysis of daily age and length patterns was carried out using the sagittal otoliths from wild larvae (0–0.2 cm standard length, L_S), pre-recruits (3–6 cm total length, L_T), recruits (7–12 cm L_T) and young adults (12–15 cm L_T). Additionally, variability in growth and age at recruitment (A_R) were evaluated for recruits caught in northern Chile in 1973, 1982, 2009, 2010, 2012, 2013, 2014 and 2015. The age–length relationship showed four allometric patterns that were well described by Laird-Gompertz models. The absolute growth rates at the inflexion point (G_AR) were 0.56, 0.75, 1.22 and 1.16 mm d⁻¹ for larvae, pre-recruits, recruits and young adults, respectively. At the interannual scale, G_AR values were always >1 mm d⁻¹ (mean ± S.D. 1.37 ± 0.21 mm d⁻¹; range 1.12–1.64 mm d⁻¹), irrespective of the season of hatching (i.e. winter v. spring); additionally, in most cases, G_AR values were reached before the second month of life (mean ± S.D. 50.47 ± 9.73 days) at c. 4 cm L_T (mean ± S.D. 4.22 ± 0.29 cm). Mean A_R was < 150 days (112 ± 29 days; range 75–149 days); in contrast, estimates of A_R were higher and growth rates were lower in 1973, 1983 and 2000. These results demonstrate very fast growth and early A_R of anchoveta in northern Chile, suggesting most fish are removed by the fisheries at very early ages. An evaluation of the implications of these results on stock assessment and management of this species is highly recommended.