Spatiotemporal analysis of the daily growth traits of the prerecruits of a small pelagic fish in response to enviromental drivers

Abstract

[eng] A comparative analysis of daily growth patterns was carried out for prerecruits (PR) of Engraulis ringens, collected from spring to summer (2015-2016) in northern (18º25'S-24º40'S) and southern nursery areas (32º40'S-41º00'S) off the Chilean coast. Prerecruits ranged from 2.2 to 7.3 cm TL (4.27 ± 0.88) and from 27 to 102 days (54.68 ± 15.92) of age and were hatched mainly in spring 2015. Growth traits were addressed through otolith microstructure analysis to determine the increment width profiles (IW), back-calculated growth rates (BIGR), and overall absolute growth rates (AGR), whereas the Chl-a and sea-surface temperature (SST) variations were assessed by analyzing satellite and field-based data. The IWs (5.42 ± 1.94 µm versus 1.02 ± 0.37 µm), BIGRs (1.02 ± 0.37 versus 0.72 ± 0.26 mm·day−1), and AGRs (0.93 ± 0.15 versus 0.62 ± 0.08 mm·day−1) were significantly higher in the northern than in the southern stocks. The SST ranged from 17°C to 23°C (19.42 ± 1.45) and from 12°C to 18°C (14.81 ± 1.31) and varied significantly between stocks and months, whereas the higher concentration of Chl-α (~8 mg/m3), occurred close to the shallow coastal areas irrespective of stocks. A parabolic relationship between the recent otolith growth rates (ROGR) (as a proxy of recent daily somatic growth rates) and SST recorded at the date of capture estimated a maximum ROGR of 13.4 µm·day−1 at 18°C. These results demonstrated that water temperature seemed to be an important daily growth controller for early juveniles of E. ringens in the Humboldt Current System and that the field-based growth-temperature relationship obtained will contribute to future potential bioenergetics models for this important forage species.