The Avilés Canyons System (ACS) is located in the South of the Bay of Biscay (Northern Spain, Cantabrian Sea) and covers a total of 3,390 km2. It is composed of three canyons, reaching the abyssal plain at 4700 m depth. The mixing of diverse water masses generates gyres and upwellings that contribute to the enrichment in nutrient concentration at different depth and favour the settlement of benthic communities. The ACS has been declared Site of Community Importance (SCI: C ESZZ12003) within the Natura 2000 Network and recognized as a Vulnerable Marine Ecosystem where echinoderms play an important ecological role in benthic communities and habitats. The aim of the present study is to inventory and review the echinoid fauna collected during the INDEMARES project in the ACS, compare the new findings with previous studies Official Spanish Checklist (IEEM: “Inventario Español de Especies Marinas”, 2017, 2020) and update our knowledge of the diversity and distribution of echinoid species. During the surveys carried out within the project LIFE + INDEMARES-Avilés Canyons System (2010–2012), a total of 287 specimens of echinoids were sampled at 35 stations and depth ranging between 510 and 1476 m. Twelve species of echinoids were identified, the most frequent being Araeosoma fenestratum (Thomson, 1872) (48.57%), Cidaris cidaris (Linnaeus, 1758) (42.85%) and Phormosoma placenta Thomson, 1872 (28.57%). One species should be considered as a new record in Spanish waters, Gracilechinus affinis (Mortensen, 1903) and the species Echinocardium flavescens expands its known bathymetric range (from 325 to 552 m).

This research has been funded by the LIFE+INDEMARES ACS project coordinated by the Biodiversity Foundation of the Ministry of Agriculture, Food and Environment and the European Union's LIFE programme. It was also supported by the Spanish Ministry of Environment through a management agreement with the Spanish Institute of Oceanography (IEO) and University of Malaga. Also, we want to recognize the effort of Dr. Francisco Sánchez and Dr. Alberto Serrano, who provide the opportunity to fund this study through the Transferring Office of the Málaga University under contract nº:2013/0032460–80625/47.6006.