Seasonal changes in growth and condition of anchovy late larvae explained with a hydrodynamic-biogeochemical model simulation

We studied seasonal changes in otolith and somatic growth and condition of anchovy Engraulis encrasicolus late larvae (8-55 mm) from the North Aegean Sea (eastern Mediterranean), hatched during the peak (summer) and end (autumn) of, and also after (winter), the regular anchovy spawning period in the area. Mean growth rate and somatic condition were compared with abiotic and biotic parameters collected in situ (current environment). Additionally, we used the output of a coupled 3D hydrodynamic-biogeochemical model implemented over the broader sampling area to reconstruct the potential conditions that the larvae experienced during their development (environmental history). Growth in length was similar for larvae in summer and autumn (0.80 mm d(-1)) but significantly lower in winter (0.63 mm d(-1)). Larval and otolith size at hatching were larger in winter. Otolith microstructure was faint in winter with very narrow increments. Otolith and somatic growth were coupled in autumn and winter, but in summer, when temperature was high, otoliths were significantly larger for the same fish length, age and weight. The biogeochemical model simulation implied that mean plankton productivity was significantly higher during the development of larvae in summer, explaining their higher growth in weight and somatic condition compared to autumn and winter. In situ measured environmental parameters represented a snapshot of ambient conditions at the site and time of sampling and did not adequately explain the seasonal differences in growth and condition.