Top-down effect in rice-fish culture using juvenile crucian carp evaluated by biota in experimental paddy fields

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  • Tsuruta Tetsuya
    Department of Environmental Science and Technology, Faculty of Design Technology, Osaka Sangyo University
  • Iguchi Kei’ichiro
    Graduate School of Fishery Science and Environmental Studies, Nagasaki University

Bibliographic Information

Other Title
  • フナ類を用いた稲田養魚におけるトップダウン効果

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Abstract

Rice-fish culture using juvenile crucian carp, Carassius complex, has been practiced in the Asian monsoon region. We investigated the influences of juvenile crucian carp on the paddy field ecosystem in an experimental paddy field with rice-fish and rice only plots. The numbers of individuals of zooplankton and benthic invertebrates were considerably lower in the rice-fish plots than in the rice only plots, indicating that these organisms were preyed on by juvenile crucian carp. Chlorophyll a values were significantly higher in the rice-fish plots than in the rice only plots. It is most likely that the increase of the phytoplankton biomass in the rice-fish plots was caused by the decrease of abundance of zooplankton and there was a top-down effect by fish foraging. The rice-fish plots also showed significantly lower biomass of aquatic weeds than the rice only plots. Presumably both soil disturbance through fish activity and enhanced phytoplankton biomass increased the water turbidity, and thereby limited sunlight penetration in the floodwater inhibited growth of aquatic weeds in the rice-fish plots. The NO3-N concentration in the rice-fish plots was also higher than that in the rice only plots, suggesting that the positive effects on growth of rice plant through the species interactions exceeded the negative effects.

Journal

  • Aquaculture Science

    Aquaculture Science 66 (4), 297-307, 2018

    Japanese Society for Aquaculture Science

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