| Abstrakt: |
The geographic and spatial distribution of ayu Plecoglossus altivelis (Temminck and Schlegel 1846) larvae were determined in the rivers of northern Vietnam. Collections were made with a larval net and a small seine net along the Tien Yen and Kalong Rivers from 2010 to 2015. Thirty individuals were collected in the Tien Yen and 160 from the Kalong. This is the first record of larval and juvenile ayu from the Tien Yen, which constitutes the southernmost range of this species. Collected fish were primarily at the preflexion stage (4.0-59.1 mm body length, BL). Mean temperature, salinity, turbidity and dissolved oxygen where larvae and juveniles were collected ranged from ca. 15.7-20.0 °C, ca. 5.6-20.7 psu, 2.7-14.6 NTU, and 7.7-10.0 mg.L-1, respectively. Larvae began to appear in November for the Kalong and in December for the Tien Yen, primarily occurring at stations far from the river mouth. Larvae <7.0 mm BL were more widely distributed across both estuaries, migrating to shoreline waters after reaching a size of ca. 15.0 mm BL in February. With relatively few larvae being observed in the southernmost region, the Tien Yen estuary may be a focus of conservation efforts of this annual amphidromous fish. [ABSTRACT FROM AUTHOR] |
