Surface-based group feeding of Indo-Pacific sailfish (Istiophorus platypterus), a highly popular species in recreational fishing worldwide, is commonly observed, yet sailfish are believed to be largely solitary roaming predators. In new research, marine biologists from the Guy Harvey Research Institute at Nova Southeastern University and Florida International University used biologging data and video to examine daily activity levels and foraging behavior, estimate metabolic costs, and document a solitary predation event for a 40-kg sailfish.
Sailfish are known for their distinctive large dorsal fins and elongated front-end bill, which gives them a built-in sword-like weapon for hunting.
These open ocean wanderers can travel both by themselves, or in groups.
Sailfish have been observed to hunt in groups on schooling fishes, using their bill in a slash, stun, and eat the baitfish sequence of actions.
This type of hunting by sailfish has been observed several times by wildlife photographers because it often occurs at the surface of the ocean, where it is easily accessible to human eyes.
However, when sailfish are not engaged in these cooperative group hunting events, they are thought to live a mostly solitary lifestyle.
Sailfish have some other pretty unique features that separates them from many other groups of fish. For example, they can keep their eyes and brain warmer than the surrounding water, which gives them an advantage over their prey when hunting in colder or dimly lit water.
But because of this, it’s assumed that they burn a lot of calories throughout the day, so one could assume that they must also need to eat in between those group hunting events, although this had never been documented.
“Most of the day sailfish dive back and forth between the surface and the thermocline layer, where the water gets cold,” said lead author Ryan Logan, a doctoral candidate in the Guy Harvey Research Institute at Nova Southeastern University.
“The…
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