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

## TL;DR

This study assesses the habitat suitability for amphioxus in coastal waters of Hebei Province, identifying key environmental factors and showing population trends over a decade.

## Contribution

The study provides long-term insights into amphioxus population dynamics and habitat requirements, using a habitat suitability index for conservation guidance.

## Key findings

- Amphioxus abundance fluctuated significantly, with a sharp decline from 2008 to 2015 followed by recovery after 2016.
- Sediment grain size, water depth, and sediment sulfide were identified as key environmental factors influencing amphioxus distribution.
- Higher habitat suitability was found in central stations, suggesting these areas are more favorable for amphioxus.

## Abstract

Amphioxus is a rare marine species that provides important clues about the origin of vertebrates and serves as a sensitive indicator of coastal ecosystem health. However, current research on amphioxus has been limited, often focusing only on abundance data from single years or specific sites, without linking population changes to environmental conditions. Studies have also rarely addressed long-term patterns or considered the combined effects of natural and human disturbances. These gaps make it difficult to understand the survival challenges of amphioxus and to design effective conservation strategies. In this study, we analyzed over a decade of observations from the coastal waters of Changli, Northern China. By linking population trends with environmental factors, our research offers new insights into habitat conditions and risks facing amphioxus. The findings highlight the value of long-term monitoring and provide scientific support for protecting marine biodiversity and ensuring the sustainable management of sensitive coastal habitats.

Amphioxus, a key model organism in vertebrate evolution, is essential for understanding ecological balance and species diversity. This study examined the spatiotemporal distribution of Branchiostoma japonicum 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.