Aphanius fasciatus as a geomorphological baseline indicator for salt marsh restoration in the Venice Lagoon

Restoration is widely recognised as a key strategy to reduce biodiversity loss, especially in transitional water ecosystems. Yet, the absence of clear ecological baselines often makes it difficult to identify suitable reference conditions for habitat reconstruction. In this study, we investigated the habitat preferences of the resident killifish Aphanius fasciatus , a species closely tied to the morphological features of Mediterranean salt marsh creeks. Monthly sampling was carried out over one year in salt marshes of the Venice Lagoon, allowing us to assess the relationship between habitat characteristics and species abundance. Results revealed that A. fasciatus favours creeks that retain water at low tide, are nutrient-rich, and exhibit high structural complexity. The species therefore represents a valuable ecological indicator, providing a practical tool to define site-specific baselines for salt marsh restoration. More broadly, our findings suggest that salt marshes with high geomorphological heterogeneity support not only A. fasciatus but also other species of ecological and commercial importance, raising the possibility that this species could act as an umbrella species for conservation and management.