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

In this study, the effect of shelter acclimation on the post-release movement and putative predation mortality of hatchery-reared black-spot tuskfish Choerodon schoenleinii was examined using acoustic telemetry. We acclimated four 1-year-old fish to shelters in cages before release and compared their movements with six nonacclimated fish. Since it was not possible to compare the behavioral pattern between the former and the latter fish due to the short periods the latter fish were available to be monitored, we also compared their movements with those of large nonacclimated fish that were less likely to be preyed upon. Sixty-seven percent of the nonacclimated fish showed atypical movements before the signals ceased to be detected, a pattern that suggested a predation event had occurred, whereas none of the acclimated and large nonacclimated fish showed the atypical movements. In addition, the probability of detection cessation was about 13 times lower in the acclimated than nonacclimated fish. The signal detection patterns suggest that the acclimated fish utilized night-time shelters from the first night after release, while the large nonacclimated fish started to utilize shelters several days after release. Therefore, it is likely that the shelter acclimation enhanced the shelter utilization by tuskfish, possibly decreasing post-release predation mortality

Mating and nesting behavior of hawksbill turtle (Eretmochelys imbricata) in captivity

December 13-14, 2006, Siam City Hotel, Bangkok, ThailandWe previously reported that two long-term reared mature females laid a total number of 894 eggs during a total of 7 nesting times. However, we did not elaborate the relationship between mating and nesting behavior. In the present study, we investigated the relationship between mating and nesting behavior in captivity. Details of the mating and nesting behavior were monitored since December 2005 by using four highly sensitive cameras continuously throughout day and night. Two cameras were fixed on the edge of the tank observation window and two cameras on the upper side tank wall connected to an artificial sand nesting bed. Rearing methods and the feeding protocol were same as the previous report (Shimizu et al., 2006). One mature male and three mature females were used for the present study. These turtles were the same turtles used for the previous study (Shimizu et al., 2006). After the nesting periods in 2004, the females did not mate with the male and did not lay eggs in 2005. One time mating was first observed after the start of camera observations in December 2005 in the two females during April to May. Shelled eggs were first observed between 13 and 18 days after mating. Thereafter the first laying was observed between 24 and 33 days after mating

A new technique for monitoring grazing behavior of Hawksbill turtles (Eretmochelys imbricata) using acceleration data loggers

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-15, 2004, Imperial Tara Hotel, Bangkok, ThailandGrazing behavior of sea turtles is important to understand their behavioral ecology. However, there is a shortage of effective techniques available for monitoring the grazing behavior accurately over a long period. In this study, the grazing behavior of hawksbill turtles (Eretmochelys imbricata) was monitored with acceleration data loggers which recorded depth, temperature, and accelerations in two axes. A Juvenile hawksbill turtle was attached with two acceleration data loggers on both head and carapace. During the experiment, we recorded the behavior of turtles on the underwater digital video camera. Their behaviors were distinguished into four patterns through the acceleration profiles and the underwater observation as follows; resting, swimming, grazing and breathing. The new technique can clarify when and where turtles graze quantitatively as well as time allocation of their behavior patterns

Dispersal processes of head-started hawksbill turtles (Eretmochelys imbricate) in the Yaeyama Islands waters, Okinawa, Japan

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-14, 2005, Siam City Hotel, Bangkok, ThailandBehaviors of five head-started hawksbill turtles (Eretmochelys imbricata) attached with ultrasonic transmitters were monitored using 12 ultrasonic receivers set up along the reef edge. The head-started turtles were reared for two years in the Yaeyama Station, National Center for Stock Enhancement. Four of five head-started turtles moved out of the monitoring area, but their movements are not linearly. The duration the four head-started ones stayed in the monitoring area ranged from 4 to 14 days. All of the head-started turtles had a circadian rhythm to their behaviors. The other head-started turtle stayed around the release point for 88 days until it was recaptured by a fisherman. There was not much difference in diving depth between the head-started and the wild turtles reported by other sites. These results indicate that the head-started turtles tend to wander aimlessly in the natural environment, although they have natures of a circadian rhythm and diving technique

Genetic diversity of the green turtle nesting populations in Yaeyama Archipelago, Japan

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandPatterns of mitochondrial DNA (mtDNA) variation were used to analyze the genetic diversity and population genetic structure of green turtle (Chelonia mydas) populations in Yaeyama Archipelago, southwestern Japan. Six mtDNA haplotypes were observed among 42 nesting green turtles. Nucleotide diversities at Yaeyama populations are higher than other sea turtle populations, reflecting all rookeries are comprised of a mixture of divergent haplotypes. Because genetic diversity is believed to represent the ability of populations to adapt or respond to environmental changes, it is important to protect Yaeyama nesting colonies for conserving this endangered species

Diel behavioral pattern of hatchery-reared black-spot tuskfish determined by acoustic telemetry in the natural environment and video observation in a fish tank

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandDiel behavioral pattern of hatchery-reared black-spot tuskfish was examined by acoustic telemetry in the natural environment and video observation in a fish tank. Nine tuskfish were monitored using acoustic telemetry for 150 days; five fish were observed in a fish tank for 2 days. In the acoustic telemetry tracking, tuskfish moved horizontally and vertically during the day; they stayed still at night. The tuskfish tended to utilize depths near the bottom both during the day and night. In the video observation, the tuskfish tended to move actively and sweep sand at bottom during the day; they tended to stay still in the crater they made during the night. These results indicated that tuskfish might make their night-time resting house by sweeping sand near structures and forage benthic preys during the day, and rest in the resting house at night

Successful spontaneous nesting of the hawksbill turtle (Eretmochelys imbricate) at Yaeyama Station, National Center for Stock Enhancement, Japan

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-14, 2005, Siam City Hotel, Bangkok, ThailandWith a view to the conservation of the natural stock of the hawksbill turtle (Eretmochelys imbricata), we carried out studies on the propagation techniques of this species. This paper deals with the spontaneous nesting of this species under rearing conditions. Adult turtles that were captured off Ishigaki Island between 1999 and 2002 were brought to the center by licensed fishermen. One adult male and three mature females were selected from 29 turtles and they were stocked in a 250kL tank that was connected to a sandy beach for nesting. The females were examined by ultrasonography throughout experimental period. The mean diameter of the follicles ranged from 1.4 - 1.7 cm from January to April; and gradually increased to 3.0 cm from which shelled eggs were laid. The shelled eggs were first observed on 2nd June 2004, but were not observed after September. In contrast, non nesting individuals had not possessed shelled eggs during the experimental period. These results indicate that the formation of shelled eggs is an indicator of nesting. The first nesting was observed on 7th June, with a total of 7 nestlings observed until September. A total of 894 eggs were obtained from two females

Dispersal movements of green turtle (Chelonia mydas) reared for one month after emergence

December 13-14, 2006, Siam City Hotel, Bangkok, ThailandThe objective of this study was to determine whether turtles reared for a period after hatching have the willingness to migrate offshore. In order to do this, the swimming behavior of green turtles (Chelonia mydas) reared for 28 to 56 days was monitored after their release from the beach. Eggs of green turtles laid on the beaches were collected and buried into an artificial beach. After their emergence, the turtles were reared for 28 to 56 days in containers. Six active and healthy looking turtles were selected and we tracked them after release from the beach. After release, the experimental turtles moved to the north, but their movements were meandering. Moreover, one turtle temporarily drifted onto the beach due to ocean current. The mean speed of movement was 0.75 ± 0.11 km/h. The distance from the beach during the experiment period was 1467 ± 460 m. Their movement speeds were significantly slower than those of frenzy turtle reported in previous studies. In conclusion, the results of the study indicated that the turtles reared for longer periods may not be able to migrate offshore as effectively as if they were released naturally from the beach

Preliminary result of ontogenetic change of wave orientation of green turtles in the initial growth stages

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandHead-starting is the practice of growing hatchlings in captivity to protect them from the high rates of natural predation that would occur in their early stage. It is concern whether the head-started turtles disperse to the open sea after the release like wild turtles. During offshore migration, hatchlings use refracted wave as an orientation cue to go straight to the open sea. This conditioned response to the wave results in movement away from land towards the open sea, because waves and swells entering shallow coastal areas are refracted until they approach a beach directly. Therefore, it is considered that the ability of orientation to the wave is an important key for their efficient migration. In order to investigate the growth stages, in which hatchlings keep their willingness to orientate toward the direction of surface wave approach, we conducted a preliminarily wave tank experiment using green turtle (Chelonia mydas) in their initial growth stages. The results of the preliminary experiment indicated that the green turtle keep the response to the wave until 2 weeks of age. We need to continue the experiment hereafter