Deep-water observation of scalloped hammerhead Sphyrna lewini in the western Indian Ocean off Tanzania

Abstract

A scalloped hammerhead Sphyrna lewini was observed opportunistically from a remotely operated vehicle 1Â m off the seabed at 1042Â m depth, during hydrocarbon exploration activities in the Ruvuma Basin off Tanzania. The observation, which occurred during night hours, is the deepest accurately recorded for this species and the first deep-water record for the Indian Ocean. The record adds support for the occurrence in deep water during night hours being a widespread and possibly common behaviour in this species, and further expands a small but growing literature that meso-and bathypelagic environments may be of greater importance to elasmobranchs previously considered to be primarily epipelagic.