#billfish

Fish video about one cool group of speedy apex predators!! :]

Today's animal of the day is the Striped Marlin (Kajikia audax)!

Photo credit: Kellon Spencer

This species of marlin can be found in tropical and temperate oceans around the world. On average, these giant fish grow to around 9.5 ft in length, but some exceptionally large individuals have been measured to be around 13.8 ft long! Females, on average, tend to be a bit larger than males. As their name suggests, these large predatory fish have a series of stripes that run down their bodies. They actually possess special cells that can contract and expand in order to change the stripes from a bluish color to a purplish one when they are excited.

Photo credit: Xavier Rufray

Striped marlins are epipelagic, meaning that they live a good distance away from the shore in the open ocean, but stick close to the surface of the water. Like the Atlantic blue marlin, which I covered on day 164#, these fish are apex predators and use their long, sharp bills to slice and stun prey. Their favorite prey seems to be sardines, though they've also been observed hunting mackerel, small tunas, and various species of squid. The streamlined bodies and powerful tails of these marlins allow them to reach speeds of over 50 mph! Meanwhile, their fins and sails help them to steer and make incredibly sharp turns while chasing after prey.

Photo credit: laurreid on iNaturalist

Hemingwaya sarissa here was one of the earliest known billfish, related to modern sailfish and marlin. Living during the late Paleocene, about 58 million years ago, it inhabited the area around what is now Turkmenistan, in the warm shallow waters of the western Tethys Sea that covered much of central Asia at the time.

It was rather small compared to its modern relatives, just 30-40cm in length (~1'-1'4"), with a long streamlined body armored with six rows of scutes. Its slender snout was lined with tiny teeth, and both its first dorsal fin and first anal fin were tall and elongated. 

It probably wasn't a very active swimmer, instead hovering near the surface and catching smaller prey with quick bursts of speed.

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Marlin, Frank Stick. Wildlife in North Carolina. September 1981.