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

Hatchery-reared Mekong giant catfish utilized deep areas in the Mae peum reservoir, northern Thailand

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandThe juvenile and young hatchery-reared Mekong giant catfish Pangasianodon gigas have been released into the 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 of the hatchery-reared giant catfish has been investigated in the Mae peum reservoir from 2003 to 2005. Our results suggest that the hatchery-reared fish primarily utilized deep areas in the reservoir. The deep areas which the fish primarily utilized may be suitable as protected areas in the reservoir

A review of the Mekong giant catfish tracking project (MCTP) from 2002 to 2004

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, ThailandFor the conservation and successful stock enhancement of the endangered species Mekong giant catfish Pangasianodon gigas, an understanding of its movement patterns and behavior is indispensable. The Mekong giant catfish tracking project (MCTP) has been begun to measure the movements of hatchery-reared Mekong giant catfish using acoustic telemetry and bio-logging technology in the Mae peum reservoir and Mekong River. Research in the Mae peum reservoir demonstrated that fish showed distinctive diel vertical movement and the swimming depth was limited by the thermocline or dissolved oxygen stratification. Fish also displayed diel horizontal movement between inshore at night and offshore areas during the day. Researchers in the Mekong River presented the first records of upstream and downstream movement of Mekong giant catfish for up to 97 days. Fish swam upstream at a speed of 16.2 km d-1 and downstream at a speed of 7.2 km d-1 during a day. These results will contribute to plans for the species conservation and the effective stock enhancement in reservoirs and fish ponds

Vertical Movements of a Mekong Giant Catfish (Pangasianodon gigas) in Mae Peum Reservoir, Northern Thailand, Monitored by a Multi-Sensor Micro Data Logger

The vertical movements of one Mekong giant catfish Pangasianodon gigas were monitored for 3 days in August 2004 using a depth-temperature micro data logger. The logger was recovered using an innovative time-scheduled release system and located by searching for VHF radio signals. The logger was found approximately 2.2 km away from the release point and provided (n=705,128) depth and temperature data collected over a period of 98 hours following the release. The fish spent more than 99% of its time at less than 3 m below the surface. The maximum swimming depth was 5.6 m. No sharp thermocline was present during the experiment. Temperature did not have any detectable effect on the pattern of vertical movement of the fish. The dissolved oxygen concentration (DO) was stratified, with a concentration of >60% saturation in the first 3 m below the surface falling to 10% saturation at depths lower than 4 m. This specific DO stratification was found to limit the vertical movement of the catfish

Feeding habits of hatchery-reared young Mekong giant catfish in a fish pond and in Mae peum reservoir

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, ThailandWe studied the feeding habits of the hatchery-reared young Mekong giant catfish released in a fish pond and Mae peum reservoir, northern Thailand. We examined the gut (stomach and intestine) contents of 5 catfish, Relative Length of Gut (RLG) of 4 catfish and plankton composition in the reservoir. The gut contents of the catfish in the fish pond consisted of a fluid like the pellets, zooplankton, phytoplankton and aquatic plants. The gut contents in the reservoir consisted of unspecified contents, zooplankton and phytoplankton. The majority of prey items were the Branchiopoda (75 % in zooplankton) and Chlorophyceae (98 % in phytoplankton) in the gut contents of the catfish in the reservoir, while the major plankton in the reservoir were copepoda including nauplius and copepodid (mean : 50 %) and eurotatorea (mean : 41 %) in zooplankton, and chrysophyceae (mean : 52 %) and chlorophyceae (mean : 38 %) in phytoplankton. It is reasonable to suppose that the catfish positively selected their major prey items if a particular prey item was found in the gut contents, contrary to the organism composition in the reservoir. However, the cuticle and the cell walls of these plankton are resistant to intestine enzymes of some fish. Furthermore, RLG of 4 catfish were greater than 1. In general, a fish is carnivorous when RLG is less than 1, while the fish is herbivorous or omnivorous when RLG is greater than 1. These results indicate that the hatchery-reared young catfish fed on the potential prey items in front of the catfish, and the catfish might not be piscivorous but planktivorous

Study on the behavior of F2 Mekong giant catfish using ultrasonic telemetry

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, ThailandThe Department of Fisheries, Ministry of Agriculture & Cooperatives of the Thai government first succeeded in producing a second generation (F2) of Mekong giant catfish Pangasianodon gigas through artificial insemination in 2001. In order to compare the behavior of F2 catfish with those of the first generation (F1), we monitored ten F2 catfish for 18 days using ultrasonic telemetry in an artificial reservoir (Mae Peum reservoir, Phayao province, Thailand). The F2 catfish stayed shallower at night and deeper during the day, and avoided hypoxia areas of the reservoir. Since this diel vertical movement was observed in the previous study on F1 catfish, F2 catfish should be as behaviorally healthy as F1 catfish