Sagittal otolith microstructure,early growth and development of Coilia ectenes in the Yangtze Estuary,China

Larvae and juveniles of Coilia ectenes were collected in the Yangtze Estuary during June through September 2009 and in May 2011. Our objectives were to reveal the otolith microstructural pattern, and then to reveal the early growth and development process through otolith analysis for C. ectenes. A total of 368 individuals, ranging 4.4–81.2 mm body length (BL) and spanning a continuum from yolk-sac larvae to early juveniles, were analyzed. There is a single primordium in the core of the sagittal otolith, surrounded by a prominent dark band (PD-band) and a wide light area (WL-area). Regular bipartite increments deposit outside of the WL-area. Similar to other Engraulidae species, the PD-band forms corresponding to hatching, increments form daily, and the first increment forms on the 3rd day post hatching, corresponding to the first feeding. The relationship of otolith radius and BL was significantly fitted to a piecewise regression with the inflection point at 34.0 mm BL. Mid-age and mid-size of transition from yolk-sac to preflexion was calculated as 5 days and 6.1 mm BL, from preflexion to flexion was 18 days and 15.2 mm BL, and from flexion to postflexion 29 days and 21.5 mm BL. Mid-size from postflexion to juvenile was 26.6 mm BL. These results can provide an essential basis for future studies on early-life ecology of this species.