Assessment of Habitat Suitability for Amphioxus in the Changli Marine Reserve and Adjacent Coastal Waters, Hebei Province

Amphioxus, a key model organism in vertebrate evolution, is essential for understanding ecological balance and species diversity. This study examined the spatiotemporal distribution of <i>Branchiostoma japonicum</i> and assessed its habitat suitability in the Changli Golden Coast Nature Reserve and adjacent coastal waters from 2008 to 2023 (excluding 2020). The maximum abundance showed marked fluctuations, with a sharp decline between 2008 and 2015 followed by recovery after 2016, reaching a peak of 345 ind./m² in 2022. The average abundance also increased, peaking at 34 ind./m² in 2022. Spatially, the higher abundances occurred in central stations, while peripheral sites were much lower, sometimes absent. Spearman's correlation and Principal Component Analysis (PCA) identified sediment grain size (1~0.25 mm), water depth and sediment sulfide as key environmental factors. A habitat suitability index (HSI), constructed using the Analytic Hierarchy Process (AHP), showed higher values in central stations, indicating more favorable conditions. These findings highlight the importance of long-term monitoring, clarify the ecological requirements of amphioxus, and provide guidance for habitat conservation and management in regions affected by environmental change and human activities.