Validation of otolith increment formation and the growth rate of fat greenling larvae

fat greenling larvae

水産増殖

We validated the daily formation 0f otolith increments of reared fat greenling Hexagrammos otakii larvae and examined the growth patterns of wild lavae. The mean notochord Length and otolith radius of newly hatched larvae were 8.31 mm and 273μm, respectively. Newly hatched larvae had some increments on their lapilli and a check was formed at hatching (hatch check). The relattonship between age and the number of increments formed outside the hatch chcck (NI)was linear regression (Nl=0.99Age-0.30, n=49, r^2=0.98, P<0.001) and its sloped did not differ significantly from 1 (t-test: P=0.31). The indicates that these increments formed daily Wild fat greenling larvae were collected from the surface layer of Mutsu Bay from February to April in 2003. The relationship between the the otolith radius (OR in μm) and notochord length (NL in mm) was represented by an allometric equation The mean back-calculated NL with the biological intercept method was 9.79mm at 10 days old, 10.9mm at 20 days old. 11.6mm at 30 days old, and 133 mm at 40 days old The daily growth rate was relatively high immediately after hatching (range: 0.15-0.17mm/day) and gradually decreased. These finding suggest that fat greenling larvae do not have a slow growth period just after hatching.