Seasonal movement of one Mekong giant catfish, Pangasianodon gigas, in relation to the environmental conditions of Mae Peum Reservoir, northern Thailand

摘要

Greater knowledge of the relationship between movement patterns of the target species and the environmental conditions (e.g., temperature and dissolved oxygen) is needed for effective fisheries management and conservation (Brill 1994, Cartamil & Lowe 2004). The Mekong giant catfish Pangasianodon gigas is one of the largest freshwater fishes in the world, measuring up to 3 m in length and weighing in excess of 300 kg. The catfish is one of the most important fisheries species of the Mekong River Basin in the Southeast Asia; however, the catch number of wild catfish in the Mekong River has declined due to development of the river and over-fishing (Hogan 2004) and the catfish currently is listed in CITES Appendix I and on the IUCN Red List of threatened species as a Critically Endangered Species.rnHatchery-reared juvenile and young immature catfish were released into lakes and reservoirs as well as the Mekong River to enhance the stock (Meynell 2003). The behavior, movement patterns, and survival rate of these catfish after release into natural conditions remains largely unknown (Meynell 2003), although that information is quite useful for fishery management and conservation decision making (Lowe et al. 2003, Humston et al. 2005).rnWe started to investigate the movement patterns of the catfish using acoustic telemetry in 2001 (Arai et al. 2005). To assess the movement patterns of the catfish during the rainy season in 2003, 8 fish tagged with acoustic transmitters were released in Mae Peum reservoir, northern Thailand in 2003 (Mitamura et al. 2008). Although 7 of 8 tagged fish had expelled the transmitters during the study period (8-136 days), the remaining one fish was monitored for more than 14 mo during both the dry and rainy seasons, which provided the movement patterns in relation to the seasonal environmental condition. There are not so many studies that continuously monitored the same fish over a year due to the same difficulties, such as fish mobility, vastness of the study site, and transmitter detachment (Lucas 1989). The objective of this study was to report the seasonal movements of one catfish in relation to environmental conditions.