Seeking the Sun in Deep, Dark Places: Mesopelagic Sightings of Ocean Sunfishes (Molidae)

Technological advances for the study of mesopelagic species have increased dramatically in recent years; from baited remote underwater videos through to remotely operated vehicles (ROVs). Although sightings of fish below surface waters decrease exponentially with depth, fleeting or unexpected encounters can sometimes provide insights into performance maxima and predator-prey associations.

Here, we present serendipitous mid-water sightings of three sunfish species, sourced from industrial and research submersibles, made available through the SERPENT project and other online resources. The remit of the SERPENT project is to connect the advanced technologies used by the oil and gas industries with marine scientists by providing anecdotal footage of marine species encountered during routine surveys.  A total of 13 sightings of Molidae, distributed from Scotland to Australia, were obtained at depths of up to 500m with a new depth record obtained for Mola ramsayi, providing further evidence of the deep ranging capabilities of this family. More broadly, these records taken together with previous ROV sightings of large oceanic predators such as hammerhead sharks, add weight to the idea that mesopelagic environments may be of greater importance than previously thought for taxa often considered as epipelagic.