Chondrichthyan observations with ROV in the Western Mediterranean and Southern Bay of Biscay

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November 11, 2009

In 2006, 2007 and 2008, Oceana employed an ROV to complete bionomic seabed surveys in the Mediterranean Sea and Bay of Biscay, between 50 and 350 meters depth. Information on positions, depths and times of observations was recorded, providing new data on the geographic distribution and bathymetric range of chondrichthyans. Fourteen species were found: five sharks, eight batoids and one chimaera. A total of 304 individuals were observed: 158 in the Mediterranean and 146 in the Bay of Biscay. The most widespread chondrichthyan observed was Scyliorhinus canicula, accounting for 69% of all observations. The densest presence of chondrichthyans in general (56.786 sightings/ hr) occurred in the Aceste seamount, Italy, due to the high number of Galeus blainvillei. The other species observed were Hexanchus griseus, Galeus melastomus, Galeus atlanticus, Dasyatis pastinaca, Torpedo marmorata, Raja clavata, Raja montagui, Raja miraletus, Raja naevus, Raja radula, Raja brachyura and Chimaera monstrosa. Galeus atlanticus was recorded for the first time in the Bay of Biscay, out of its recorded distribution range of the Alboran Sea, Strait of Gibraltar and surrounding European and African Atlantic waters. The use of an ROV in underwater investigations helps us better understand the chondrichthyan populations which live at deeper depths.

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