A GEERG expedition recently used a sonar-equipped VideoRay ROV to locate sharks in the murky waters of the St. Lawrence. A VideoRay ROV located several specimens in an effort to reduce search time on scuba in poor visibility. The VideoRay was also used to locate and report the position of sharks in total darkness during a night dive. Our belief that the Greenland shark is a stealth predator was confirmed when VideoRay pilot Brian Luzzi recorded a shark swimming beside the divers while they were unaware of its presence. Not seeing sharks does not mean they aren't there.

Chris Harvey-Clark holding a VideoRay GTO with BlueView 900khz Imaging Sonar. Images courtesy Brian Luzzi / VideoRay

Natural sonar

A GEERG team diving in the St. Lawrence may have documented for the first time a sperm whale hunting for Greenland sharks. An adult sperm whale* was observed diving at a site where large numbers of Greenland sharks are believed to congregate. When the dive team entered the water, the same whale was recorded (audio) using echolocation to pinpoint prey on the bottom. The distinctive clicks produced by the unseen whale were audible to the ear when the dive team observed a four-metre female S. microcephalus swimming unusually fast (more than 0.5 m/sec.). Although the sperm whale mainly feeds on cephalopods, it is also known to hunt benthic sharks on occasion and this may be what was taking place just out of sight of the GEERG divers.

* The sperm whale observed by GEERG is believed to be an individual locally known as Tryphon, who was also observed by a GEERG team at the same location in 2005.