Notopterus notopterus
Notopterus notopterus is distributed throughout the area of
the present survey, from the Mekong delta to Chiang Saen in
Chiang Rai province, Thailand. Fishermen throughout its distribution
range reported that the species only undertakes localised lateral
migrations from the Mekong River to floodplains during the flood
season, and back to the main river
or other permanent water bodies during the dry season. Many
fishermen, especially in Cambodia, stated that the species was
more common in permanent lakes than in the main river channel.
Further upstream, in the Lao PDR and Thailand, the species is common in the Mekong mainstream as well as its tributaries, living in pools with submerged wood and shrubs. At several places, it was reported to move into tributaries during the flood season, where it apparently spawns.
Reports on eggs showed a strong peak in May (14 reports) and June (11 reports). Two fishermen in Viet Nam also reported observing eggs from September to November. Furthermore, two fishermen (one from Khemmaratch in Thailand, and one from Sambor in Cambodia), reported separately that the species spawns twice per year.
Three fishermen reported spawning behaviour. Two fishermen in Viet Nam observed spawning in flood-plain habitats (flood-plain grassland and flood-irrigated ricefields, respectively). One fisherman in Khemmaratch observed spawning in mainstream pool habitats, with the eggs attached to submerged vegetation.