A review of elasmobranch breaching behavior: why do sharks and rays propel themselves out of the water into the air?

Abstract

The elasmobranch fishes, both the sharks and rays, which inhabit the underwater environment, display breaching behaviors consisting of their sudden propulsion out of the water and into the air. They then land on top of the sea surface, displacing water upon contact. At other times, they do not completely clear the water, but partly so, performing a lunge rather than a clear jump or breach. These behaviors have been reported in the scientific literature for the fast-swimming predatory sharks, but also for a slow-swimming planktivorous shark as well as many of the rays. We identify breaching behavior in species in the selachan families, Alopiidae, Carcharhinidae, Cetorhinidae and Lamnidae, and batoidan families, Mobulidae, Aetobatidae, Myliobatidae, Rhinopteridae, and Dasyatidae. We present and discuss evidence in support of the following functions: (1) parasite removal, (2) clearing of gill rakers, (3) expulsion of feces or internal parasites, (4) courtship, (5) attraction of conspecifics, (6) repelled by conspecifics and interpecifics, (7) evasion by conspecifics, (8) feeding, (9) concentrating or stunning of prey, and (10) birthing. Our recording of this behavior has evolved beyond simple observations and now incorporates information gathered through advanced technologies, such as animal-borne data loggers, digital photography, and observations from aerial or underwater drones. Within this context, we review the relevant literature, describing studies and research to provide additional insight into the causation of these behaviors.