Swordfish

About the Swordfish

In the cut-throat arena of the ocean twilight zone, the broadbill swordfish is the undisputed champion. Rushing its victims at great speed, the swordfish slashes larger prey with its distinctive, swordlike bill, then gobbles them up. Smaller prey are likely swallowed whole.

Like some tuna and shark species, swordfish maintain relatively high body temperatures even in the deep, cold water of the ocean twilight zone. Special heat-producing organs warm their large eyes and brain as much as 15 ℃ (59 degrees ℉) above ambient temperatures—a trait that lets their nervous system work faster in cold water. As a result, swordfish are quickly able to spot the movement of their prey, even in the dim light and near-freezing temperature of the twilight zone. When competing with cold-blooded fish for squid, their favorite snack, this gives them a serious advantage. The internal heater also protects the swordfish’s brain from rapid temperature and pressure changes as they zoom around the ocean. Though swordfish are comfortable at ocean depths of 800 meters (2,600 feet), they’re sometimes seen basking or breaching at the surface. They spawn in the upper ocean in water temperatures above 23 ℃ /73 ℉. Aside from this brief period when they get close enough for external fertilization to happen, the swordfish swims alone.

Reaching sizes of 4.5 meters (almost 15ft), the enormous size and crowd-pleasing flavor of swordfish make them popular with both recreational and commercial fishers. Conservation efforts in the late 1990s helped the North Atlantic population bounce back from over-fishing while also reducing the numbers of undersized swordfish, sea turtles, and bluefin tuna that are accidentally caught in commercial long-lines.