The white marlin (Kajikia albida), also known as Atlantic white marlin, marlin, skilligalee, is a species of billfish that lives in the epipelagic zone of the tropical and subtropical Atlantic Ocean. They are found between the latitudes of 45° N and 45° S in waters deeper than . Even though white marlin are found in bodies of water that are deeper than 100 m they tend to stay near the surface. White marlin have been found near banks, shoals, and canyons, but they are not limited to those locations. They prefer warm surface temperatures greater than .
Identification
White marlin are commonly misidentified as roundscale spearfish (Tetrapturus georgii). This likely caused a miscount of the population size of white marlin and roundscale spearfish before they were determined genetically different in 2001.
Taxonomy and evolution
In 1860, Felipe Poey gave the white marlin the name Tetrapturus albidus. This classification places the species in the same genus as shortbill spearfish, Mediterranean spearfish, roundscale spearfish, and longbill spearfish. Researchers have identified fossils from the genus Tetrapturus dating back to the Langhian Age 15 million years ago (Mya). Extinct ancestors, such as species from the genus Palaeorhynchus date to as early as 56 Mya. Today, Kajikia albida and its close relative Kajikia audax (striped marlin) have been scientifically determined to be genetically distinct from the species in the genus Tetrapturus.
Appearance and anatomy
White marlin are mid-sized billfish with a bill that is round in cross section, and distinctly forked caudal fin. Though all white marlin have the same coloring pattern, they are sexually dimorphic, with the females usually larger.
Fishing and conservation
Prior to 2001, roundscale spearfish and white marlin were identified as the same species. Researchers from Nova Southeastern University's Guy Harvey Research Institute, Dania Beach, Florida, first discovered that these two species were significantly different in 2001 through genetic tests. Before this discovery. the two species made up a population that was of least concern to the IUCN. Placement into the endangered species list was not established until 2007, when the population numbers had already dropped below easily recoverable levels.
White marlin fishing is a multimillion-dollar organization in well-developed countries. Restrictions are in place to limit the size of fish that can be taken, but the angling process can be devastating to fish. The time spent on the hook, outside handling, dehooking, and releasing a white marlin exhaust enough energy that up to 32% of the time, the marlin cannot maintain buoyancy in the water. When fishing for any billfish, use of a circle hook, which can be dehooked more quickly than other hooks, is recommended. In the U.S. Atlantic, Gulf of Mexico, and Caribbean waters, the fish is required by federal regulations to be kept in the water, boatside, to maximize its chances of surviving after release. Research indicates that removing a billfish from the water may increase their risk of death after release by ~30 percent (research ongoing).
About 90% of the annual catch is caught accidentally in bycatch from fishing around the world.