Local knowledge of the Mekong giant catfish at the Sirikit Dam Reservoir, Northern Thailand

December 13-14, 2006, Siam City Hotel, Bangkok, ThailandSome 103, 276 hatchery-reared Mekong giant catfish have been released into the Sirikid dam reservoir from 1984 to 2006. Local knowledge of the catfish was assessed from two fishermen at the reservoir in December 2006 and March 2007. Both fishermen used a gill net to capture the Mekong giant catfish. The experience of one fisherman suggests that the catfish might move around the old channel in the reservoir. The Mekong giant catfish captured in this reservoir by the other fisherman varied from 40 to more than 100 kg in weight. This suggests that the Mekong giant catfish might have grown greatly in the Sirikit dam reservoir and have been a fishery resource around the Sirikid dam reservoir basin

Hatchery-reared F2 Mekong giant catfish spent their time above hypoxic water in the Mae Peum reservoir, Thailand

March 5-6, 2009, Bangkok, ThailandJuvenile and young hatchery-reared Mekong giant catfish Pangasianodon gigas have been released into reservoirs throughout Thailand. For the sustainable reservoir fishery of the giant catfish, new science-based fishery management measures are expected in Thailand, such as the establishment of protected areas. Therefore, the habitat use and movement patterns of the hatchery-reared giant catfish have been investigated in the Mae Peum reservoir from 2003 to 2005. Our results suggest that the hatchery-reared fish spent their time in shallow depths above hypoxic water in the reservoir. The fish which have been reared in a fish pond may recognize and avoid hypoxic conditions

Water temperature and precipitation stimulate small-sized Japanese eels to climb a low-height vertical weir

Although river-crossing structures can have a detrimental effect on the movement and distribution of anguillid eels (genus Anguilla), they have inhabited locations upstream of river-crossing structures in many rivers. However, the growth stage in which the eels start to climb river-crossing structures remains unclear. In this study, we directly observed, using infrared video camera systems, that the Japanese eel (Anguilla japonica) climbs a low-height vertical weir as a migratory barrier, confirming the ability of eels to climb over a low-height weir within a river. All eels climbed the weir at night, between sunset and sunrise. We observed that the total length of Japanese eels that climbed the weir ranged from 60 to 140 mm, suggesting that eels inhabiting the upstream area of a weir climbed it when they were small and then lived and grew upstream. Moreover, the general additive model showed considerable effects of water temperature and precipitation on eel climbing, suggesting that water temperature and precipitation are important for its activation. The results of this study also show the effectiveness of infrared video cameras in monitoring eel climbing, which could be applied to monitor fish migratory behavior through fish passages. The findings of this study are useful for the comprehensive management and conservation of wild eel stocks

Study on behavioral characteristics of wild and hatchery-reared red tilefish

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, ThailandThe diel activity of red tilefish Branchiostegus japonicus was studied using two different methods : analysis of biotelemetry records and video observation. We have acquired the biotelemetry tracking records of the red tilefish which were released in Maizuru Bay and tracked from January 2003 to February 2004. The records ware compared to the time of sunrise and sunset, the duration of sunshine, and the lunar cycle, which may influence on light conditions. Whilst the fish showed diel activity, the fish changed their behaviors along with the time of sunrise and sunset; the fish probably moved out of their burrows in the daytime and retreated into the burrows at night. We could not find a clear relationship between the behavior and the other two factors. In the laboratory, the behavior of one hatchery-reared individual was recorded by video for five days in the experimental tank where the light condition changed periodically over 24 hours. The fish was more active in the light periods (550 lx) compared to in the dark periods (0 lx). Since the results from the two methods probably compliment one another, further experiments using the two methods will reveal the detailed behavior of red tilefish

A rare species of Uropterygius (Anguilliformes, Muraenidae) found in the stomach content of a yellow-lipped sea krait from Japan

A single muraenid specimen (genus Uropterygius), recovered from the stomach of a live Yellow-lipped Sea Krait, Laticauda colubrina (Schneider, 1799), captured at Iriomote Island, Japan, was found to possess intermediate traits between 2 rare species, Uropterygius xenodontus McCosker & Smith, 1997 and Uropterygius golanii McCosker & Smith, 1997. The specimen is provisionally identified as U. xenodontus and is described below with its morphs, as an important addition to material of rare specimens of the genus in the western North Pacific

THE ULTRASONIC TRACKING OF MEKONG GIANT CATFISH PANGASLANODON GIGAS IN MEKONG RIVER

Southeast Asia Sea Turtle Associative ResearchBangkok, Thailand, 16-19 December 2002The Mekong giant catfish Pangasianodon gigas is endemic to the Mekong River, measuring up to 3 m in length and weighing in excess of 300 kg. The number of the wild catfish in the Mekong River has decreased due to the development of the Mekong River these days. Therefore, ecological researches are urgently needed to conserve the catfish. However, there was no method to monitor the movement of the catfish continuously in the Mekong River. The objective of this study was to test a feasibility of coded ultrasonic tracking system to monitor the contineous movement of the catfish in such a large river, the Mekong River. We released ten cultured catfish in the Mekong River. The catfish tended to move downstream or stayed around the release point just after the release. Four of ten catfish moved upstream for 60 km in 2-3 days although one fish moved downstream for 40 km. This tracking system that we tested could be a feasible system to monitor the continuous movement of the catfish in such a large river, the Mekong River

Striped catfish (Pangasianodon hypophthalmus) exploit food sources across anaerobic decomposition- and primary photosynthetic production-based food chains

Dietary information from aquatic organisms is instrumental in predicting biological interactions and understanding ecosystem functionality. In freshwater habitats, generalist fish species can access a diverse array of food sources from multiple food chains. These may include primary photosynthetic production and detritus derived from both oxic and anoxic decomposition. However, the exploitation of anoxic decomposition products by fish remains insufficiently explored. This study examines feeding habits of striped catfish (Pangasianodon hypophthalmus) at both adult and juvenile stages within a tropical reservoir, using stable carbon, nitrogen, and sulfur isotope ratios (δ¹³C, δ¹⁵N, and δ³⁴S, respectively) and fatty acid (FA) analyses. The adult catfish exhibited higher δ¹⁵N values compared to primary consumers that feed on primary photosynthetic producers, which suggests ingestion of food sources originating from primary photosynthetic production-based food chains. On the other hand, juvenile catfish demonstrated lower δ¹⁵N values than primary consumers, correlating with low δ³⁴S value and large proportions of bacterial FA but contained small proportions of polyunsaturated FA. This implies that juveniles utilize food sources from both anoxic decomposition and primary photosynthetic production-based food chains. Our results indicate that food chains based on anoxic decomposition can indeed contribute to the dietary sources of tropical fish species

Global trends in aquatic animal tracking with acoustic telemetry

Acoustic telemetry (AT) is a rapidly evolving technique used to track the movements of aquatic animals. As the capacity of AT research expands it is important to optimize its relevance to management while still pursuing key ecological questions. A global review of AT literature revealed region-specific research priorities underscoring the breadth of how AT is applied, but collectively demonstrated a lack of management-driven objectives, particularly relating to fisheries, climate change, and protection of species. In addition to the need for more research with direct pertinence to management, AT research should prioritize ongoing efforts to create collaborative opportunities, establish long-term and ecosystem-based monitoring, and utilize technological advancements to bolster aquatic policy and ecological understanding worldwide

バイオテレメトリー ジョウホウ ニ ヨル メコンオオナマズ ノ コウドウ ニ カンスル ケンキュウ

京都大学0048新制・課程博士博士(情報学)甲第11810号情博第170号新制||情||37(附属図書館)23550UT51-2005-F840京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, 教授 片井 修学位規則第4条第1項該当Doctor of InformaticsKyoto UniversityDA