Seasonal patterns of larval settlement and daily otolith increments in the temperature wrasse Halichoeres tenuispinis.

Abstract

Seasonal patterns of larval settlement were studied in the temperate wrasse Halichoeres tenuispinis at Tsuyazaki, Fukuoka Prefecture, Japan, during the period from July through November, 1987. The “settlers” (juveniles smaller than 15mm TL) started to appear on the rocky reef in late July and increased in number suddenly in early August, attaining more than 600 individuals within the transect (100m2). The number decreased in late August and the “juveniles” (15-40mm TL) increased their number in turn. Otolith (sagitta) marking with a fluorescent substance in “juveniles” revealed that the increments are formed daily. Hatched larvae had a clear hatching check in the otoliths. By counting increments exterior to the hatch check in 101 specimens collected during the period from July 27 to September 7, 1987, an equation In Y=0.023X+1.782, where Y=total length and X=number of increments, was obtained. It was estimated that the shortest duration of planktonic life in the present species is 26 days after spawning. Back calculated dates of birth of these specimens fell within a relatively short period from June 7 to July 25.