In their study of Mekong fish migrations, Poulsen (2000) and Bao et al. (2001) found that
in the case of all species, a change in water level was the most important factor associated
with both longitudinal and lateral migration. Fishers from Khone Falls also say that at the
beginning of the rainy season the change in water level is the single most important factor
determining the catch of migrating fish (Viravong et al., 1994). However, it is also noted that
the dry season migration seems to be less under the influence of changing water levels and
climatic conditions than the May-June migration that proceeds the flood.