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The effect of food competition on diet shifts and growth of silver and bighead carps
In situ study on effect of food competition on diet shifts and growth of silver and
bighead carps in large biomanipulation fish pens in Meiliang Bay, Lake Taihu
By Z. Ke, P. Xie and L. Guo
Donghu Experimental Station of Lake Ecosystems, State Key Laboratory for Freshwater Ecology and Biotechnology of China,
Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan, China
Summary
Silver and bighead carps were cultured in large fish pens to
reduce the risks of cyanobacterial bloom outbreaks in Meili-
ang Bay, Lake Tauhu in 2004 and 2005. Diet compositions and
growth rates of the carps were studied from April to
November each year. Both carp species fed mainly on
zooplankton (50% in diet) in 2004 when competition was
low, but selected more phytoplankton in 2005 when compe-
tition was high. Silver carp had a broader diet breadth than did
bighead carp. Higher densities and fewer food resources
increased diet breadths but decreased the diet overlap in both
types of carps. It can be predicted that silver and bighead carps
would be released from diet competition and shift to feed
mainly on zooplankton at low densities, decreasing the
efficiency of controlling cyanobacterial blooms. Conclusively,
when silver and bighead carps are used to control cyanobac-
terial blooms, a sufficiently high stocking density is very
important for a successful practice.
Introduction
Silver carp (Hypophthalmichthys molitrix) and bighead carp
(Aristichthys nobilis) are two large-bodied planktivorous cyp-
rinids that are intensively cultured in Asia. They comprise
much of the carp aquaculture production in China (Liang
et al., 1981). Food habits of silver and bighead carps and their
effects on the plankton communities have been widely reported
(Spataru, 1977; Cremer and Smitherman, 1980; Starling and
Rocha, 1990). In general, bighead carp is considered an
opportunist, feeding more on zooplankton, whereas silver carp
feeds mainly on phytoplankton (Cremer and Smitherman,
1980; Chen, 1990). B
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