Dynamics of nutrients, plankton and benthic macroinvertebrates in rohu Labeo rohita ponds with various densities of common carp Cyprinus carpio
Common carp (Cyprinus carpio) is specialized to feed on benthic organisms and in doing so affects nutrient availability, which enhances photosynthesis. Therefore, it is commonly used in polyculture pond to increase natural food for planktivorous fish. However, high density of common carp increases s...
| Main Authors: | , , , , , , |
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| Format: | Conference or Workshop Item |
| Language: | English |
| Published: |
2008
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/38150/ http://irep.iium.edu.my/38150/1/Korea_2008b.pdf |
| Summary: | Common carp (Cyprinus carpio) is specialized to feed on benthic organisms and in doing so affects nutrient availability, which enhances photosynthesis. Therefore, it is commonly used in polyculture pond to increase natural food for planktivorous fish. However, high density of common carp increases soluble P precipitation and water turbidity, which reduce photosynthesis and the related natural food production. Considering both positive and negative effects, stocking density of common carp is important. In this study, we monitored the N, P, phytoplankton, zooplankton and benthic macroinvertebrates dynamics and fish yield in rohu (Labeo rohita) (density: 1.5 m-2) ponds with various densities of common carp (0, 0.5 and 1 m-2; further referred as 0C, 0.5C and 1C, respectively) under fed and unfed conditions. The ultimate objective was to optimize a fish combination and density for South Asian carp polyculture farmers.
All treatments were executed in triplicate and the observation period was 4.5 months. We observed that the greater water N and P concentrations in ponds with common carp than the ponds without common carp (P<0.05). P concentration in pond water was greater in lower than higher density of common carp (P<0.05), whereas common carp density had no effect on N concentration in pond water. Phytoplankton and zooplankton bio-volumes in ponds were greater in lower than higher density of common carp, followed by without common carp (Fig. 1-A, 1-B) (P<0.01). Total benthic macroinvertebrates bio-volume decreased with increasing common carp density (Fig. 1-C) (P<0.01). The combined gross fish yield per pond was greater in lower density of common carp (3,532 kg ha-1 137 days-1) than higher density of common carp (3,030), followed by without common carp (1,747) (P<0.01). The positive effects of stocking 0.5 common carp m-2 were lost partially when stocking 1 common carp m-2. P concentration, and phytoplankton and zooplankton bio-volumes were more or less increased with increasing time in ponds with 0.5 common carp m-2, whereas there was no significant trend of P concentration, and phytoplankton and zooplankton bio-volumes in ponds with 1 common carp m-2 and without common carp. In ponds with common carp, the biovolume of benthic macroinvertebrates did not increase with increasing time (Fig. 1-C). The results suggest that an additional planktivorous fish can be added with 0.5 common and 1.5 rohu m-2 to increase further fish yield by optimum utilizing of phytoplankton and zooplankton. |
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