Identifying spawning events in the Japanese flounder Paralichthys olivaceus from depth time-series data

Vertical swimming events (VSEs) of the Japanese flounder, Paralichthys olivaceus, recorded by high-frequency depth data loggers, were analysed to identify spawning events. In total 25,907 VSEs from 10 adult fish were classified into 4 clusters using a k-means method. VSEs in a specific cluster (cluster-S) characterised by accelerated vertical swimming were identified as possible spawning events. Both the descent (0.43 ± 0.22 body length s− 1) and ascent rates (0.43 ± 0.24 body length s− 1) of VSEs in cluster-S were more than 4 times faster than in any other VSE. Our analyses indicated that 4 individuals exhibited the spawning events during the recording periods. The estimated spawning frequency ranged from 0.74 to 0.90 events day− 1. These values were comparable to those obtained in other field and laboratory studies. The spawning condition of fish at the time of recapture was confirmed by separate histological and anatomical observations, which supported the cluster analysis results. These results suggest that a clustering technique can be successfully applied to identify spawning behaviour from time-depth data of free-swimming flatfishes that exhibit vertical swimming movements

Depth utilization and swimming speed of female green turtles at Huyong Island, Thailand

March 5-6, 2009, Bangkok, ThailandThe resident depth and swimming speed of female green turtles Chelonia mydas nested at the Huyong Island, Thailand were examined. Four types of data loggers were used to record depth and swimming speed of turtles during the inter-nesting period with an interval of 1 second. Field experiments were conducted from 2003 to 2007 and the data was obtained from a total of 10 turtles. The turtles used the depth between 0 and 92.72 m and the mean resident depth ranged from 6.27 ± 6.29 to 20.66 ± 9.47 m (n = 10 turtles). Mean swimming speed of the turtles ranged from 0.04 ± 0.09 to 0.27 ± 0.25 m s-1 (n = 5 turtles). The nesting rookery and female green turtles at the Huyong Island are protected by the National Acts in Thailand. However, tour boats can go on a cruise around the island, suggesting an impact accident between boats and turtles. Therefore, the data on shallow depth utilization and the slow swimming speed of the turtles obtained through this study provide important information for the proper implementation of conservation of the green turtles

カイヨウ ドウブツ ホゴ クイキ ノ ヒョウカ ノ タメ ノ セイタイ ジョウホウ ノ シュトク ト カイセキ : アンダマンカイ アオウミガメ オ モデル ケース ト シテ

京都大学0048新制・課程博士博士(情報学)甲第13203号情博第247号新制||情||51(附属図書館)UT51-2007-H476京都大学大学院情報学研究科社会情報学専攻(主査)教授 守屋 和幸, 教授 田中 克己, 助教授 荒井 修亮学位規則第4条第1項該当Doctor of InformaticsKyoto UniversityDA

INTERNATIONAL CONSERVATION AND MANAGEMENT OF STRADDLING STOCKS INCLUDlNG SEA TURTLES

Southeast Asia Sea Turtle Associative ResearchBangkok, Thailand, 16-19 December 2002Wildlife including sea turtles in the ASEAN countries has faced the extinction due to rapid economic development of human being. We have started to study to clarify the ecology of green turtles in Gulf of Thailand and Andaman Sea to prevent their extinction. Satellite tracking of the sea turtles indicates that the turtles migrate from Thai waters to other countries' waters including Brunei, Cambodia, India, Indonesia, Myanmar, Malaysia, and Vietnam. It is very important to install Turtle Excluder Devices (TEDs) and to analyze the relationship between turtle's habitats and human activities to avoid the incidental catch by fishing gears. In addition, it is also important to share the information on sea turtle ecology among the countries using computers

Fine-Scale Tracking of Marine Turtles Using GPS-Argos PTTs

High-accuracy location data of wildlife telemetry using conventional satellite location systems are difficult to obtain. However, such data are necessary to clarify the nature of movements and home range sizes of animals. In order to measure the high-accuracy location data, we developed new GPS-Argos Platform Terminal Transmitters (PTTs) which transmit both the conventional location and GPS location simultaneously. Two experiments, one in an artificial rearing pond and the other in the open sea, were performed. First, two hawksbill turtles were tracked with the PTTs in a 5 ha breeding pond in Thailand. Their home ranges using both data were calculated and found to be 2.96 ha and 0.93 ha by the GPS data, and 156,740 ha and 184,478 ha by a conventional data. Secondly, a female green turtle attached with the GPS-Argos was released from the coast of Pangnga Province, Thailand. There was a relationship between depth and speed of travel based on the GPS data. The data from the PTT showed that the turtle moved south along the coastline at the depth of less than 20 m for 5 days, and then stayed at a depth of less than 10 m for 4 days. However, we could not find any clear relationship using conventional data. Only a meandering movement at a variety of depths was observed. The results of the two experiments indicated the PTTs have an enormous potential for enhancing our understanding of fine-scale movement patterns and home ranges of marine turtles

A female green turtle at Huyong Island rests at the drop off

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, ThailandThis paper gives preliminary results of diving behavior for one female green turtle during an inter-nesting period at Huyong Island in Thailand. A depth/temperature logger was used to examine the habitat utilization of the female green turtle during an inter-nesting period at Huyong Island in Thailand. In general, it has been believed that female turtles during this period rest at shallow water (typically less than 20 m) because they save energy for the nesting activities. However, time-series of depth for the female turtles at Huyong Island indicated that she sometime dived into the deep area (more than 20 m) although she tried to save energy by performing U-shape diving. A relationship between dive depth and dive duration suggests the deep dives were not resting dives. Previous satellite tracking study indicated that they stayed near the Huyong Island during this period. According to these results, female turtle used a reef edge or a drop-off, as their habitat during inter-nesting period

Seasonal nesting of green turtles at Huyong Island, Thailand

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, ThailandIn this paper, we report the current results of the studies on the reproductive biology of green turtles nested at Huyong Island, Thailand. The Huyong Island is a year-round nesting rookery of green turtles. Although information on year-round nesting population of sea turtles is very important to understand the ecology of sea turtles, there were few comprehensive data sets on year-round nesting populations. Therefore, three methods were used to investigate reproductive features of year-round nesting population of green turtles. Firstly, tagging studies were conducted to examine nesting seasonality of female green turtles. Next, satellite tracking studies were conducted to examine horizontal distributions of the female green turtles during post-nesting periods. In addition, bio-logging studies using data loggers were used to examine diving behavior of the female green turtles during inter-nesting periods. Our results showed that: 1) nesting in the Huyong green turtles occurred more or less at the same time on an individual basis, 2) nesting throughout the season might be attributed to proximity to feeding grounds, 3) there is seasonal difference in reproductive output among individuals, and 4) diving behavior of females during inter-nesting periods may be a key determinant of the seasonal difference in reproductive output

Difference in Flipper Beating Frequency of Green Turtles in Water and on Land

March 18-19, 2013Sea turtles spend most of their lives in marine habitats, but they require a terrestrial environment for oviposition. In both conditions, they use limbs for thrust production. We attached animal-borne data loggers on green turtle and calculated the stroke frequency during swimming in water and crawling on land from surging acceleration. Stroke frequency was compared during swimming and crawling. The results showed that stroke frequency during terrestrial crawling is significantly higher than during swimming. This contrasts with previous studies of animals performing drag-based swimming. Because green turtles are considered to be lift-based swimmers that produce thrust mainly by dorsoventral excursion, one hypothesis is that anteroposterior excursion may be restricted despite its importance in terrestrial crawling and drag-based swimming. Small anteroposterior excursion resulting in short stride length may be complemented by higher stroke frequency during crawling

Vertical distribution of water temperature around female green turtles during the internesting period

December 13-14, 2006, Siam City Hotel, Bangkok, ThailandTime-depth-temperature data loggers were used to examine the vertical distribution of water temperature and diving behavior of female green turtles, Chelonia mydas, during the internesting period at Huyong Island in the Andaman Sea. The Andaman Sea of western Thailand experiences two main seasons: the relatively calm dry season from November to April and the stormy rainy season from May to October. The dry season is characterized by a north-easterly dry wind off the Asian continent. In contrast, heavy rain and strong winds characterize the rainy season. The vertical profile of ambient water temperatures showed that a thermocline did not develop in the dry season. In the rainy season, water temperature was stable to about 30 m, suggesting that an ocean surface mixed layer had developed. All turtles dived continuously during the internesting period. Dive depth ranged from 12.25 ± 6.24 m (n = 193) to 20.30 ± 10.95 m (n = 137) in the dry season and was 23.13 ± 16.32 m (n = 777) in the rainy season

The Relationship between the Number of Breaths and Diving Profile of a Nesting Green Turtle, Chelonia mydas

March 18-19, 2013In this study, the relationship between dive duration, activity level during the dive and the number of breaths during post-dive surface duration of one free-ranging nesting green turtle, Chelonia mydas, was examined using two acceleration data loggers. Breathing was extracted from the static acceleration and depth data of the head-mounted data logger. The overall dynamic body acceleration (ODBA), which has been used as an index of activity levels per unit time of a dive, was calculated from tri-axis dynamic acceleration data of the carapace-attached data logger. The number of breaths during post-dive surface duration divided by ODBA significantly increased with longer dive duration. The number of breaths during post-dive surface duration divided by dive duration significantly increased with larger ODBA during a dive. The results suggest that the number of breaths was regulated by dive duration and activity level during a dive