Nippon Suisan Gakkaishi 75 (2), 191-197 (2009)

Effectiveness of Paddy Fields as an Initial Growth Environment for Larval and Juvenile Nigorobuna Carassius auratus grandoculis

SHIGEFUMI KANAO,1,2* TAISUKE OHTSUKA,3 MASAYOSHI MAEHATA,3
NORIYASU SUZUKI4 AND HIROICHI SAWADA5

1Taga Town Museum, Inukami, Shiga 522-0314, 2Graduate School of Environmental Science, The University of Shiga Prefecture, Hikone Shiga 522-8311, 3Lake Biwa Museum, Kusatsu, Shiga 525-0001, 4Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507, 5School of Enviromental Science, The University of Shiga Prefecture, Hikone, Shiga 522-8311, Japan

Carassius auratus grandoculis larvae and juveniles were released in paddy fields near Lake Biwa. Later, they were periodically collected and subject to growth analysis of total length (TL) and body weight (BW). As a result, daily growth rates in both TL and BW reared in paddy fields were high in comparison to those of fish reared in fishery ponds and raised naturally in reed zones of Lake Biwa. The survival rate of C. a. grandoculis in paddy fields increased with lower population density. Meanwhile, daily growth increments shifted from an increase to a decrease at 11-24 days of age in TL, and at 15-44 days of age in BW. Therefore, paddy fields are considered to be highly effective as an initial growth (until about 40 days of age) environment for C. a. grandoculis.


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