Southern Australia represents a global biodiversity hotspot for the Syngnathidae (seadragons, seahorses, and pipefishes), a family designated as globally threatened due to industrialisation, habitat degradation and commercial bycatch. Cockburn Sound in southwestern Australia represents an ecological contradiction: it supports an exceptional syngnathid assemblage while concurrently serving as a major industrial port and naval facility slated for significant infrastructure expansion.
To quantify species richness and distribution of these small and highly cryptic fishes within this heavily utilised embayment, we compiled data using a range of methods across more than 100 years. We aggregated and validated 4,839 occurrence records from diverse historical and contemporary sources, including museum voucher specimens, peer-reviewed literature, unpublished reports and historical notebooks, contemporary SCUBA surveys, scientific trawl surveys, community-sourced citizen science, and environmental DNA (eDNA) metabarcoding assays. We confirmed the presence of 21 syngnathid species within a spatial footprint of ~200 km². Common or easily recorded species contribute significantly to the dataset, while small and behaviourally cryptic species are data-poor.
This establishes Cockburn Sound as a globally significant refuge for syngnathid fishes within a marine biodiversity hotspot. Remarkably, this high diversity persists despite decades of extensive anthropogenic modifications to the marine environment. Our findings indicate the possibility of divergent species-specific responses to industrial presence. Specialist taxa likely exhibit heightened vulnerability to localised extirpation, while other generalist species may benefit from microhabitats provided by artificial maritime infrastructure. Consequently, future port development and ongoing operations necessitate targeted mitigation frameworks. Minimising ecological impacts requires addressing specific environmental concerns, including direct mechanical interactions, benthic habitat loss (e.g., seagrass meadows), increased turbidity, anthropogenic underwater noise, and the proliferation of marine pests. Despite this extensive dataset, many species remain poorly documented, so balancing strategic infrastructure operations with the conservation of these fishes remains a critical management priority.