Cyprinids were sampled, by electrofishing,
from 159 sites on small rivers in four
major watersheds across central Thailand. Total
abundance, estimated by the depletion method,
varied directly with water velocity and, inversely
with discharge while species richness varied inversely
with habitat width and, directly with
ambient oxygen and alkalinity. Numerical abundance
of cyprinids was well above that for any of
the other 27 families of fishes represented in the
catches. Incidence of occurrence was high only for
a few cyprinid species in each watershed with
most species present in £10% of the sites. Across
all sites, cyprinids represented approximately
35% of all species captured and were absent from
only two sites. Species richness was highest in the
Maeklong watershed. Canonical correspondence
analysis identified five significant habitat variables,
temperature, habitat width, discharge,
ambient oxygen and alkalinity, and the extent to
which each influenced the distribution of the 41
cyprinid species. The results are discussed in