Wallago leeri
Although Wallago leeri appears to be less common than the congeneric Wallago attu, it has almost the same distribution range, i.e., from about 50 km from the Mekong delta to the northernmost stations in Thailand.
Like its relative, Wallago leeri attains sizes larger than 90 cm. One fisherman in Chiang Khong, northern Thailand, said the species attains a maximum weight of 80 kg. The maximum size recorded by Rainboth (1996) was 145 cm.
The present survey produced limited data on the migrations of this species. The data on downstream migrations nevertheless follows a general pattern. In Cambodia, downstream migrations begin in May and end in July. Fishermen at one station in the Lao PDR and one station in Thailand concurrently reported that Wallago leeri migrates downstream during October-November. The data for the timing of upstream movements are too sparse to allow any interpretation. Fishermen in the Lao PDR and Thailand agreed that Wallago leeri migrated into smaller streams to spawn. One Lao fisherman reported that the fish migrated in groups. One Thai fisherman explained that the species could normally be found in small Mekong tributaries when the water level started rising, especially after heavy rain. Detailed information on the movements of this species in Cambodia and Viet Nam is not available.
Eggs were observed in the abdomen of the fish from April to October, with the majority of observations being reported between May and July.
One fisherman in Chiang Khong reported personally observing the spawning of Wallago leeri. He also reported that Wallago leeri spawns in flooded grassland in July, that it spawns at night, and that it breed in deeper water than Wallago attu. When breeding, the fish swim in pairs, and the eggs are spawned near the surface.