Abstract
The ayu (Plecoglossus altivelis) is an annual, amphidromous,
plecoglossid fish, distributed in Vietnam, China, Taiwan, Korea, and Japan. To
date, ayu have been found only in two rivers in northern Vietnam, where little
is known about their life history. The Tien Yen River is believed to be the
most southwestern habitat for this species. To determine whether newly hatched
ayu larvae drift and to understand their downstream migration, intensive
surveys were conducted in the Tien Yen River from October to March of 2013–2016.
In total, 529 drifting ayu larvae were collected from four of six sampling
stations along the river. Thus, ayu reproduction has been confirmed in this
river for the first time, where only adult fish had been found previously.
However, we did not successfully collect larvae in the eastern branch of the
river, which has a hydroelectric dam, suggesting that ayu do not inhabit this
branch or else do not reproduce there. The presence of drifting larvae in the
western branch from mid-December to late January implies that they spawn from
late November to mid-January. Drifting larvae were captured primarily at night,
but peak occurrences varied depending upon the day and the sampling station.
With the range of body sizes and variable diel abundance patterns, ayu in the
Tien Yen River probably employ multiple spawning grounds. This study provides
fundamental life history data for the vulnerable ayu populations in northern
Vietnam.
Fulltext: https://doi.org/10.1007/s10641-017-0646-6
(Source: https://www.proquest.com/scholarly-journals/downstream-migration-newly-hatched-ayu/docview/1949494227/se-2?accountid=28030)