Current Population, Habitat Status and Species of Amphioxus in Dongshan Bay, Fujian Province

Dongshan Bay, along with Xiamen Bay, serves as a significant distribution area for amphioxus in Fujian Province. In this survey, we observed that the sedimentary environment of Dongshan Bay has been seriously silted due to rapid economic development and the thriving aquaculture industry. Consequently, there has been a significant reduction in suitable habitats for amphioxus and a sharp decline in its resource abundance. Totally 9 amphioxuses were collected from its eastern region in 2022 with a population density of 18.75 ind m⁻² and a body length from 34.15 to 48.02 mm. The amphioxuses acquired in this investigation were classified as Branchiostoma japonicum based on morphological traits, such as a cuspate rostral fin, measurements of angles between the dorsal and super-caudal fins, angles between the pre-anal and sub-caudal fins, along with an accurate count of pre-anal fin chambers which matched those observed in B. japonicum. Moreover, a molecular barcoding analysis was conducted using a fragment of the mitochondrial COI gene. The results indicated that Branchiostoma sp. from Dongshan Bay in this study belongs to B. japonicum, providing additional support for the morphological identification results. Considering amphioxuses are still surviving in Dongshan Bay despite the destruction of their habitat, it is recommended to implement measures to safeguard their resources and habitats. The measures may include designating protection areas, strengthening law enforcement management to prohibit sand mining, regulating the scale of cage aquaculture, and augmenting wild resources through artificial breeding and release.