Spying on the devil’s lair: Seasonal aggregation of the sickle fin devil ray species Mobula tarapacana at an offshore seamount in The Azores, Portugal (Mid-North Atlantic), using a novel methodology.

Jorge Manuel Moreno Mendoza

Seamounts are biodiversity hotspots for pelagic and oceanic species like the sickle fin devil ray, Mobula tarapacana. As such, this endangered (IUCN) species aggregates every summer at Princess Alice Seamount and Ambrosio Seamount in the Azores archipelago . The aim of our research was to investigate the aggregation at Princess Alice using a non-invasive cost-effective methodology. A stationary camera system was used to gain insight into the daily pattern of abundance and overall season abundance of the species. Furthermore, generalized linear models were tested to assess the anthropogenic and environmental effects. The results showed that the time of departure of the species from the seamount was Mid-September. Additionally, the daily pattern of abundance showed an increase in the evening periods in contrast with the mornings. The diving industry  impact was found not significant, while the environmental model showed interesting preliminary results. Despite some limitations, our research has validated this non-invasive methodology to study the aggregation of Mobula tarapacana at Princess Alice seamount, providing valuable information regarding the overall abundance during the season and the daily pattern of abundance. Furthermore, this methodology showed great monitoring potential to gain valuable ecological knowledge from a wide range of species in different contexts and locations.