Megabenthos Underwater Video (MUV): a new device to evaluate species distribution in hard-to-reach marine areas

A device, called Megabenthos Underwater Video (MUV), was designed and built for the counting and the size estimate of benthic organisms in hard-to-reach areas. Since 2014 Cassiopea andromeda, an invasive alien jellyfish in the Mediterranean Sea with benthic behavior, colonized a recreational harbor (Cala) of Palermo with a stable population. Studying the species distribution in this area with classical methods (such as visual census, ROV, etc.) was not applicable due to the large presence of obstacles (ropes, anchor cables, boats) and to dive difficulties in these types of area. The MUV was tested from 2017 to 2018 for the study of the spatial-temporal distribution of C. andromeda in the Cala. The species was distributed in the internal and intermediate zones and at depths between 1.5 and 7.5 m, with the most representative sizes ranging from 5 to 15 cm in diameter of umbrella. The greater density of individuals was observed in February 2018. The device has proved effective to collect data on density and size of a megabenthic organism in hard-to-reach areas and its use is suggested in several other environments.