We examined the effects of fertilization using fermented chicken manure on zooplankton occurrence and seed production of big-scaled redfin
Tribolodon hakonensis in four ponds (including two control ponds) during 12 June-19 July, 2013. A total of 15 species of zooplankton occurred and a Cladocera,
Moina macrocopa, was the dominant species before the introduction of
T. hakonensis larvae. The densities of Ploimida and Cyclopoida were higher in control ponds than those in seed production ponds. More than 100 individuals/100
ml M. macrocopa was observed in the ponds during 8-16 days after fertilization (DAF), which started from 11 June 2013, and the highest density was 1,801 individuals/100
ml at 9 DAF. After the release of
T. hakonensis larvae at 14 DAF, the densities of
M. macrocopa decreased rapidly within several days, presumably due to predation by fish larvae, but those densities in control ponds were constant levels until 31 DAF. A higher survival rate (96% vs. 51%) of
T. hakonensis juveniles was observed in a pond with higher abundance of
M. macrocopa before the feeding of artificial diet. Our findings suggest that monitoring of zooplankton abundance before and after the release of larvae is important for
T. hakonensis seed production.
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