The post‐release process of establishing stable home ranges and diel movement patterns of hatchery‐reared black‐spot tuskfish Choerodon schoenleinii

Abstract

Post-release change of home ranges and diel movement patterns of hatchery-reared black-spot tuskfish Choerodon schoenleinii were examined using ultrasonic telemetry. Nine hatchery-reared C. schoenleinii were released in Urasoko Bay, Ishigaki Island, Okinawa, Japan and monitored using ultrasonic telemetry. The fish gradually increased home ranges for c. 3 months before establishing stable home ranges. This pattern of home-range change might have been associated with the learning process of natural environments and intraspecific and interspecific competition. The fish also showed strong diurnal movement patterns: moving horizontally and vertically during the day and staying in the same place at night. The behaviour observed in this study is highly valuable to determine when, where and how to release the fish as well as how to increase the fitness of the fish before releasing.

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

“…3; Table 3). Type A: the signals of two of the three AC (AC1 and 4; 66.7%), one of the six NAC (NAC1; 16.7 %) and five of the five LNAC fish (LNAC4-7 and 9; 100%) showed diurnal movements in the restricted ranges (1-4 receivers) which are typical to the black-spot tuskfish [14,15], before the cease of the detection (Fig. 3a).…”

“…One-year-old tuskfish were larger than the tuskfish considered to be used in an actual stocking (10-100 mm TL) because the smallest fish size that could be successfully implanted with the smallest acoustic transmitters was around 120 mm TL when the study was conducted (See Vemco Ltd. home page: One transmitter was surgically implanted into the abdominal cavity of each fish under anesthesia using 0.1% 2-phenoxyethanol, in accordance with the Japan Ethological Society guidelines for the experimental use of animals (see Kawabata et al [14] for details). After surgery, fish were placed in a black circular 1000-l polyethylene tank for 3-8 days and monitored for postsurgical effects.…”

“…To achieve the objective, we acclimated the fish to shelters in a cage before release, and monitored 5 their movements with non-acclimated fish, using acoustic telemetry. Since it was not possible to compare the behavioral pattern between the acclimated and non-acclimated fish due to the short monitoring periods of non-acclimated fish, we also compared their movements with those of large non-acclimated tuskfish that were less likely to be preyed upon, monitored in 2006 and 2007 [14].…”

“…The ecological knowledge of the tuskfish in Okinawa Prefecture has been accumulated. 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].…”

“…With the advent of acoustic telemetry using automated monitoring receivers and coded acoustic transmitters, the movements of target species can be continuously monitored without active tracking [14,15,[22][23][24][25]. After the target species implanted with a transmitter is preyed upon, the transmitter is retained in the predator's gut for a certain period [22].…”