Anglerfish are found deep off of the U.S. coastline as well as throughout the oceans of the world. Anglerfishes live in deep oceans with no sunlight, extremely high pressure, and frigid temperatures. Anglerfish are found near a light source and deep seas, where sunlight does not reach.
Anglerfish live between 20-30 years. Female anglerfish have a longer life expectancy than males, with the numbers being about 25 years and 21 years, respectively. Anglerfish live longer in captivity than in the wild, but the difference is small because anglerfish have few predators.
Some of these fish live away from the seafloor, making them pelagic, while some live close to the seafloor, making them benthic.
There are over 200 species of fish, most of which live in the muddy depths of the Atlantic and Antarctic Oceans, as much as one mile beneath the surface. However, a few are found in the shallower, tropical environments. The 300+ highly diverse species of anglerfish live anywhere from the shallows to super-deep waters and are so named because they are fish that use louvers, which are heavily modified spines of the dorsal fins that have been moved into their snouts.
While their stunning (and, admittedly, somewhat disturbing) looks have brought widespread attention to these fish, we do not yet know much about anglerfish biology since they live in waters often too deep for scientists to access. While found worldwide, anglerfish are somewhat elusive, reclusive creatures – par for the course for a fish that lives between 1,000 feet and 16,400 feet (300 meters to 5,000 meters) beneath the surface.
How Anglerfish Feed Themselves
Anglerfish also have a knack for drawing smaller fish towards them, making them an easy target once lured closer. Not only do female anglerfish frequently eat their mates, but they will also swallow prey as large as two times their size.
Most certified female anglerfish have a rod-like structure called an illicium that they use to attract prey and lure in males for mating. Anglerfish use their other senses to move, locate prey, and entice mates. Anglerfish are also known sometimes to swim upside down, their anglers hanging down, a technique used to lure their prey.
While an anglerfish may eat living prey, a portion of an anglerfish’s diet is also made up of eating dead fish and other wildlife. Crustaceans and fish (prawns, specifically) make up most of the anglerfish’s diet.
Younger anglerfish typically eat invertebrates, while older ones switch between invertebrates and fish. Some anglerfish are remarkable for their extreme sexual dimorphism, with a slight male with a much larger female, seen in the Ceratiidae suborder, deep-sea anglerfish. The anglerfish has some of the most significant sex differences in the animal kingdom. Anglerfish females mate once per season, though whether males copulate with more than one female is unknown.
Gender Differences Between Anglerfish
A male Anglerfish lives on nutrients from a female while continuing to hunt and feed. Once the male anglerfish has reached a certain age, its digestive system is not working anymore, so it has to find a female.
The male anglerfish will nip at the female’s back and bond, with both fish merging into a single organism and creating one bloodstream. Male anglerfish, much smaller than their female counterparts, bite into a female’s body, bonding throughout their lives. Eventually, the male’s body will melt away from the female, merging into its skin and bloodstream. Although the couple forms a tight, physical union together, the female will drop eggs into the water while the male releases his sperm to fertilize them.
In some species, the male becomes a permanent parasite of the female, with his tiny body left only to trail along the water next to hers. Some male angling fish depend entirely on the female for their sustenance; their circulatory systems fuse, so they share the same blood, and in effect, the male becomes a living testicle couple. When the male anglers reach adulthood, their digestive systems are weakened, so they merge with the female by connecting their skin, bloodstream, and organs.
In other angler fish, the male is closer to the female’s body size, only meeting her for mating. In many species of deep-sea anglerfish, says McKenzie Gerringer, males are typically ten times smaller than females, with no function beyond reproduction. Male ceratoid fish are considerably smaller than females, making it difficult to find food in the deep sea.
Anglerfish Behaviors in the Wild
Born in the murky world of the deep sea, the males of some species of anglerfish only exist to snort their mates. Female anglerfish and juvenile males are creatures of opportunity, typically adapting to eating animals found within their habitat. Habitat Anglerfish inhabit the oceans from depths of 0-1,000 meters, rarely dropping below the continental slope.
The organs are presumed to serve the apparent purpose of drawing prey into the murky, deep-sea environment. Still, they also draw the attention of males towards most adult keratoid anglerfish to aid in mating. The sensitive olfactory organ helps a male to detect the pheromones signaling a female anglerfish closeness.
When its favored female partner is ready to reproduce, the male anglerfish is conveniently already there to fertilize its eggs, which will deposit into a nesting raft that will rise in the sunlit waters of the open ocean.
As of right now, we cannot tell why the male anglerfish has adopted such a bizarre immunity system, but it seems probable that it is tied to their abnormal breeding habits somehow.