Observations of Mammalian Predation on Pacific Sleeper Sharks in Southeast Alaska

ABSTRACT

The predator–prey relationship between marine mammals and sharks may not be as well defined as originally believed. Both groups can be either predator or prey. In the case of the Pacific sleeper shark, previous studies have documented the sharks predating upon juvenile Steller sea lions and scavenging whale falls, while other studies have reported offshore killer whales predating upon Pacific sleeper shark. Here, we report two observations of likely marine mammal predation upon Pacific sleeper sharks in Southeast Alaska; one of Steller sea lions actively predating upon an approximately 2 m shark; and the other a stranded carcass of a 3 m shark likely predated by killer whales. The observations reported herein are unique in that Steller sea lions have not been documented to predate upon Pacific sleeper sharks, and previous reports of killer whale predation upon Pacific sleeper sharks have been near open ocean passages.