DAPHNIA AND COPEPODS IN CULTURE PONDS
From: Liu Fengqi fengqi@mail.zlnet.com.cn
To: <CRUST-L@VIMS.EDU>
Sent: 22 August 2000
QUESTION:
We plan to produce Daphnia to feed larvae of freshwater fishes. But sometimes in the outdoor ponds, there is a small population of Copepods coexisting with the Daphnia. How to eliminate the Copepods from the Daphnia culture ponds?
Liu Fengqi
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COMMENTS 1 :
Have you tried strong lights at night? Some Daphnia species are
negatively phototactic.
We have available about 225,000 kg of fresh frozen Daphnia pulicaria
that are naturally enriched with Aphanizomenon flos-aquae. The
Daphnia are available in 25 pound HDPE pails. We have tested the
Daphnia on freshwater fishes and more recently they have been used as a
complete substitute for Artemia in PL-2 stages onwards in shrimp culture.
Howard W. Newman
Desert Lake Technologies, LLC
www.rossha.com
www.desertlake.com
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COMMENTS 2:
I guess copepods maybe have lower production efficiency than cladocera,
and copepods maybe have negative effect on the growth of cladocera. In
rotifer cultures in brackish waters, copepods can prey on rotifers. When
copepods appear in outdoor earthern rotifer culture ponds, the rotifer
production will decrease.
Copepods and rotifers have different tolerance to high
eutrophication, we can easily eliminate the copepods from the rotifer
ponds by adding suitable amount of urea to the ponds. Today a professor
told me that cladocera also have higher tolerance to high eutrophication
than copepods. So we will try our old method to eliminate copepods. What
is your idea on this point?
I have another question as follows: We plan to produce cladocera in
early spring when the water temperature in outdoor ponds is about 5-10°C.
The professor told me that Daphnia and Moina can reach a high population
only at higher water temperature (15-18°C). I wonder whether there
are some species of cladocera that have the ability to reproduce and grow
rapidly at lower water temperature (5-10°C)?
Liu Fengqi
E-mail: fengqi@mail.zlnet.com.cn
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