Abstract Six floating 4-m
3
cages stocked with 40 silver carp
per cage (three cages) and 40 bighead carp per cage (three
cages) were placed in each of the three subtropical Lakes
Phewa, Begnas, and Rupa. The fish were cultured, without
supplying artificial feed, from August 1994 to December
1995. Fish growth was positively correlated with water
temperature, and a slight loss in weight occurred in January
when water temperature fell below 16°C in all the lakes.
Fish growth was better in Lake Phewa than in Lakes Begnas
and Rupa, where food might not have been sufficient or of
a quality to sustain fish growth. The fish fed on mostly
indigestible phytoplankton, Microcystis aeruginosa in Lake
Begnas and on Tabellaria fenestrata and Microcystis
aeruginosa in Lake Rupa, which can lead to poor fish
growth. The maximum growth rate of silver carp (5.8 g
day
21
) and bighead carp (4.7 g day
21
) occurred in Lake
Phewa when Ceratium hirundinella and Peridinium spp.
were abundant from August through October. The food
particles found in the gut were mostly similar in silver and
bighead carp, though Cladocerans (Bosmina longirostris)
were observed sparsely in the gut contents of bighead carp
only.
Key words Silver carp and bighead carp · Fish growth ·
Plankton community · Subtropical lakes