From citizen science to spatial modelling: conservation implications for Hippocampus hippocampus and Hippocampus guttulatus along the Italian coasts.

Understanding the global distribution and habitat preferences of endangered animals is key to ecology and wildlife conservation. Seahorses’ conservation is of global concern as they face multiple threats such as habitat degradation/loss, climate change, bycatch and direct exploitation. Here, we aim to merge an extensive citizen science survey along the Italian coasts with spatial modelling to inform the current and future distribution of Hippocampus hippocampus and H. guttulatus. Additionally, we investigated to what extent the distribution of the two species are covered by the Italian network of protected areas through gap analyses. Our study collected 52 and 67 presence records by citizens for H. hippocampus and H. guttulatus, respectively. All these records were validated by both a photographic and a GIS approach, leading to the current most complete dataset of seahorses occurrences compared to iNaturalist, GBIF, OBIS and ACQUAMAPS. Both seahorses exhibited a preference for habitats including Posidonia oceanica, corals and algae. Spatial modelling showed that the Italian coasts are currently environmentally fit for both species but such a suitability will decline in future. The gap analyses highlighted that H. hippocampus and H. guttulatus requires more extensive protection efforts than is currently granted along the Italian coasts. Our study indicates that both seahorses urgently need improved conservation actions and shows how spatial approaches can facilitate assessments of the conservation status of endangered organisms.