Movements of Acoustic-Tagged Wild Adult Catfishes in the Mekong River, Thailand and Lao PDR

Acoustic telemetry was used to monitor the movements of wild Silurid and Pangasiid catfishes in the Mekong River in northern Thailand and Laos in 2006 and 2007.  Twenty fish from five species were tagged and released in the main stem Mekong River in May 2006 and monitored with 17 acoustic receivers along a 100 rkm reach between the Golden Triangle region, Thailand and the Thai-Laos border.  Overall, 18 (90%) of the tagged fish were detected by the fixed-site receivers.  Detection dates were highly variable, ranging from about one day for Hemibagrus wyckiodies, Pangasius conchophilus and Pangasius boucourti to more than 350 days for Bagarius yarelli.  The longest movement was by a H. wyckiodes which traveled 71.2  km from the tagging site, while the longest upstream movement was  53.2 km by a B. yarelli.   Movement rates were also highly variable ranging from 0.1 to more than 32 km/d.  The need for information about the migratory behavior of this catfish and other migratory fishes in the Mekong River is especially acute, because proposed dam developments, overfishing and habitat degradation now threaten fish populations that are a key source of protein to millions of people.