Otolith development and daily increment formation in laboratory-reared larval and juvenile black-spot tuskfish Choerodon schoenleinii

Abstract

Microstructures of lapilli were examined for reared larvae and juveniles of black-spot tuskfish Choerodon schoenleinii. Lapilli of larvae at 1 day after hatching have one diffuse and obscure ring with an otolith radius of 4.3 ± 0.50 lm (mean ± SD, N = 8). The slope and intercept of the regression between the number of days after hatching and increment counts did not differ significantly from one and zero, respectively, indicating that lapillus increments were formed on a daily basis after hatching. There was an ontogenetic shift in the relative values of somatic and otolith growth, which corresponded to the transition from pelagic larvae to settlement stage. Simultaneously, the daily increment width reached the maximum value. These findings suggest that age at maximum value of increment width can be used as an indicator of the planktonic larval duration while settlement mark is not found. Since ontogenetic shift in the relationship between otolith radius and body size was observed, backcalculation of somatic growth in black-spot tuskfish using the otolith radius during the early life stages should be analyzed with caution, and the method requires further validation.

Pelagic early life stages promote connectivity in the demersal labrid Choerodon rubescens

“…This prediction is based on the fact that pelagic larval durations (PLD) in congeneric labrids in similar geographic locations tend to be similar (Victor, 1986) and the PLD of the Blackspot Tuskfish Choerodon schoenleinii, which co-occurs with C. rubescens, is about 25-30 days (Yamada et al, 2009). Preliminary analyses of the number of growth rings between the nuclei and settlement marks in otoliths of C. rubescens support this prediction (K. Cure, pers.…”

“…rubescens is a broadcast spawner with buoyant eggs (Fairclough, 2005), which probably hatch in one to two days, like those of C. schoenleinii (see Yamada et al, 2009). The relatively protracted duration of the pelagic ELS provides considerable potential for dispersal and thus gene flow (see Shanks, 2009), possibly across the entire distribution of the species.…”

Growth, sex ratio, and maturation rate with age in the blackspot tuskfish Choerodon schoenleinii in waters off Okinawa Island, southwestern Japan

“…Because of the species's importance, stock enhancement is being tried [5]. Studies of home ranges and diel movement patterns [6], and otolith microstructure [7] using hatchery-reared individuals have also been carried out. According to these studies, the species exhibits protogynous hermaphroditism in accordance with changes in body color, like many other labrid species.…”

Effect of shelter acclimation on the post-release movement and putative predation mortality of hatchery-reared black-spot tuskfish Choerodon schoenleinii, determined by acoustic telemetry

“…This species shows a clear diurnal movement pattern; it feeds on benthic prey during the day and rests in shelters at night [13][14][15]. The fish settles around seagrass beds after the pelagic larval periods of about a month [16] and stayed there during the summer [17,18]. Thereafter, the fish gradually moves out of the seagrass beds to the sandy gravel areas as the fish grows [17,18].…”