Daily Growth Increments in Otoliths of Japanese Anchovy Larvae Engraulis japonica

Abstract

It was verified that daily deposition of increments in otoliths was initiated with the start of feeding in reared Japanese anchovy larvae. The range and the coefficient of variation of counts within age group were 2-5 and 6-10%, respectively and did not vary with age. The deposition rate of increment was considered to be independent with growth rate. The width of each increment was 1-2 μm around the nuclear margin and increased gradually to 6-9 μm, corresponding to the appearance of subdaily rings. The otolith growth was allometric with respect to the standard length. The relatinship between otolith radius and standard length seemed to be linear in log-log plot. As daily increments observed in field-collected larvae were easier to count than those of laboratory-reared ones, the determination of field-collected sampls based on daily increments was expected to have a satisfactory accuracy.