Notes on morphology and spatio-temporal distribution of early-stage juveniles of Acanthopagrus pacificus (Sparidae) in the estuary of northern Vietnam

摘要

Acanthopagrus pacificus is a commercially important fish in the coasts of western Pacific. Its early stages show potential variation in morphology and seasonal occurrences by different oceanography, even though little work has been reported. This study aims to provide morphological characteristics and spatio-temporal distribution patterns of early-stage juveniles of this species in the estuary [Tien Yen (ca. 21° 20' N)] of northern Vietnam, which is located in the middle region of the distributional range. They were characterized by the presence of prominent supracleithral and posttemporal spines, relatively deeper body, large head and eyes, which useful to distinguish them from other Acanthopagrus early juveniles. The juveniles appeared in April, reflecting the seasonal occurrence around winter and spring in northern Vietnam. They occurred in the waters where salinity ranged from<0.05 to 16.6 PSU, respectively. This result indicates A. pacificus early juveniles that colonized the shallow banks of the estuary extended to freshwater habitat.