Age and Growth of Diaphus brachycephalus in the South China Sea Using Sagittal Otolith Microstructure

Abstract

To obtain the growth and age characteristics of Diaphus brachycephalus in the South China Sea (SCS), specimens of D. brachycephalus were collected by a mid-water trawl in January and June 2015. The relationship between standard length (L) and body weight (W) was W = 0.00002699L2.8789, with no significant differences between the two survey stations and the sexes. Microscopic observation of the sagittal otoliths revealed that the daily growth increments in each period were divided into the central zone, middle zone, and external zone. The age was determined by summing the daily growth increments of the three areas. The von Bertalanffy growth curve fitted to the relationship between age and L was shown as: L = 65.6[1 − exp{−0.0132(t − 6.94)}], r2 = 0.935. The growth rate decreased from juvenile to adult, with a maximum rate of 0.436 mm day−1. The back-calculated hatching dates of specimens were speculated to be from March to November, but predominantly occurred from April to May and from September to October.