DanOlsen2018mayO297shark lo res.jpg

Offshore killer whales

 

Offshores are a genetically and acoustically distinct type of orca that specialize in predation on Shark.  Here in Alaska, Pacific Sleeper Sharks make up the majority of prey items that we find when Offshores are feeding.  Pictured above is a salmon shark in the mouth of an Offshore.

Currently we are working with Canada's Department of Fisheries and Oceans to publish a new science paper regarding Offshore diet.  Over 90% of observed diet has been shark, and the bulk of that has been Sleeper Shark.  Also on the list are Blue Shark, Dogfish, Salmon Shark, and far less commonly Halibut, Chinook Salmon, and other fishes. 

Offshores have more rounded dorsal fins at the top and have many small notches.  They also be identified by their calls, which allow us to detect them on autonomous year round hydrophones.

DSC_7621 notches copy 3.jpg

While the population size for Offshores is difficult to assess, DFO Canada investigates the relative rate at which documented and undocumented offshores are encountered.  Estimated total numbers of offshores in the North Pacific for 2014 range from 257-373 individuals.