The impact of nigorobuna crucian carp [Carassius auratus] larvae/fry stocking and rice [Oryza sativa]-straw application on the community structure of aquatic organisms in Japanese rice fields
2010
Yamazaki, M., National Agricultural Research Center, Tsukuba, Ibaraki (Japan) | Ohtsuka, T. | Kusuoka, Y. | Maehata, M. | Obayashi, H. | Imai, K. | Shibahara, F. | Kimura, M.
We examined the effects of predation by Nigorobuna Carassius auratus grandoculis larvae and fry, a crucian carp endemic to Lake Biwa, Japan, on the community structure of aquatic organisms in rice fields. Six experimental plots with three different rice-straw treatments in the presence/absence of stocked larvae were prepared. In each plot, the number of aquatic organisms ranging in size from 30 microm to 5 mm in the water, as well as those from 63 microm to 5 mm in size in the surface sediments, was surveyed 6, 13, 20, 26, 34 and 41 days after the onset of irrigation. Three-day-old fish larvae were released on day 10. Undigested organisms in the gut contents of the larvae or fry were identified on days 20, 26, 34 and 41, respectively. Ten-day-old larvae mainly preyed on Cladocera, but the fry thereafter shifted to Diptera as their main prey. While Cladocera and Podocopida decreased in fish-stocked plots, Euglenales and Halteriida became more abundant there. Top-down or bottom-up effects of fish seemed to control these changes in community structure.
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