Received: 31-05-2021 / Accepted: 09-12-2021
Coastal fisheries play an important role for local residents. The Ba Lat estuary is a significant area for aquatic organism recruitment or serves as nurseries for many fish species. Beloniformes has 275 species of 6 families in the world and 30 species of 3 families in Vietnam. Many species occur in estuarine habitats, even inhabit freshwater, but little is known about their early stages. The present study aims to provide species composition of larvae and juveniles of this order, and examine their distribution in estuary and mangrove forests. From 431 collected specimens, primarily postflexion larvae and juveniles (5.0-174.6 mm body length)during surveys between 2018 and 2020 using a small seine net at 19 stations along the bank water of the Ba Lat estuary of the Red River, the study identified five species of this order (i.e.,Strongylura strongylura, Hyporhamphus limbatus, Hyporhamphus far, Zenarchopterus buffonisandZenarchopterus sp.). This is the first record of early stages of Beloniformes in the Ba Lat estuary, northern Vietnam. Larvae and juveniles of the Beloniformes appeared at all stations (many were distributed at stations with mudy-sand, sandy-mud bottoms and mangrove forests), mainly in the rainy season, at the mean temperature range of 23.1-31.6C and salinity 0.1-12.5‰. They showed different tendencies in distribution patterns indicating that bottom sediments, water temperature, salinity and mangrove forests were important factors related to the distribution of larvae and juveniles of the Beloniformes in the study site. Especially, occurrences of two abundant species, H. limbatus andZ. buffonis, would have been an evidence for the distribution pattern of early stages of the Beloniformes in the Ba Lat estuary.These findings are valuable for conservation, exploitation and culture of species of this order in Vietnam.