@article{oai:soar-ir.repo.nii.ac.jp:00002224,
 author = {北野,  聡 and 山形,  哲也 and 市川,  寛 and 小林,  尚},
 journal = {信州大学教育学部附属志賀自然教育研究施設研究業績},
 month = {Mar},
 note = {Density of Japanese medaka Oryzias latipes was surveyed in an irrigation-ditch around paddy fields in the northern Nagano prefecture after one-year abandonment of cultivation. A total of 270 individuals of eight species (seven native and one exotic species) were captured in the study area. Japanese medaka was predominant fish in the irrigation-ditch. The density and population size of medaka were estimated at 4.9 individuals per ㎡ and ca. 9,000～12,000 individuals, respectively. Comparisons of the population data between successive years suggested that the medaka population around paddy fields had drastically decreased after abandonment of cultivation., Article, 信州大学教育学部附属志賀自然教育研究施設研究業績 (40): 29-32(2003)},
 pages = {29--32},
 title = {長野県北部の水田用水路に生息する淡水魚類：耕作放棄1年後の状況},
 volume = {40},
 year = {2003}
}