Migration patterns of Japanese dace Pseudaspius hakonensis in and around Lake Biwa, Japan are unknown, although fluvial–lacustrine life history has been known in most tributaries, the many mature individuals migrating upstream into tributaries in early spring. Field surveys and stable isotope analyses were used to clarify the migratory history of Japanese dace in the Ishida River, inflowing to Lake Biwa. In the field surveys, the number of young of the year (YOY) individuals caught per unit effort (CPUE) by hand net and casting net in the tributary and lake-shore area was calculated. The CPUE peaked from May to July, after the spawning season, thereafter decreasing rapidly, suggesting that YOY Japanese dace migrated downstream to Lake Biwa immediately after emerging, possibly due to the abundant food resources there. From September to November, the CPUE of YOY individuals increased in the lower reaches of the stream, although their stable nitrogen isotope values were variable, in some cases being similar to those recorded in the upper reaches and the lake-shore area. This suggests that some YOY individuals migrate upstream from the lake in autumn. In the present study, the juvenile migration pattern of fluvial–lacustrine Japanese dace in Lake Biwa was described using a CPUE survey and δ¹⁵N and δ¹³C analyses.

日本daPseudaspius hakonensis的迁移方式尽管在大多数支流中都知道河流-湖泊的生活史，但在日本琵琶湖及其周围地区仍是未知的，许多成熟的个体在早春向上游迁移到支流中。野外调查和稳定的同位素分析被用来阐明流入琵琶湖的石田河中日本da的迁徙历史。在实地调查中，计算了在支流和湖岸地区通过手工网和铸造网捕获的年年轻人（YOY）人数（每单位工作量（CPUE））。在产卵季节结束后，CPUE在5月至7月达到顶峰，此后迅速下降，这表明YOY日本猿猴刚出现后便向下游迁移到了琵琶湖，这可能是因为那里的粮食资源丰富。从九月到十一月 YOY个体的CPUE在河流下游增加，尽管其稳定的氮同位素值是可变的，在某些情况下与上游和湖岸地区记录的相似。这表明某些YOY个人在秋天从湖中向上游迁移。在本研究中，使用CPUE调查和δ描述了琵琶湖河流-湖相日本da幼鱼的迁徙模式¹⁵ N和δ ¹³ Ç分析。