Anglerfish (order Lophiiformes) are a diverse group of marine fishes known for their distinctive hunting strategy. Many species feature a bioluminescent lure, or esca, which is a modified dorsal fin ray used to attract prey in the dark depths of the ocean. Anglerfish size varies wildly depending on the specific species and habitat, ranging from tiny, thumb-sized organisms to large, bottom-dwelling giants.
Size Differences Across Anglerfish Species
Anglerfish size is linked to its environment, creating a distinction between shallow-water and deep-sea species. The largest members are benthic, or bottom-dwelling, species found in shallower waters. For example, the European Monkfish (Lophius piscatorius) can reach lengths of up to 6.6 feet (200 centimeters) and weigh over 127 pounds (57.7 kilograms). These large, flattened fish live partially buried in continental shelf sediment, relying on camouflage to ambush prey.
Deep-sea anglerfish (suborder Ceratioidei) inhabit the vast, open water column and are generally much smaller. Most species in this group are less than a foot long. The largest deep-sea females, such as Krøyer’s deep-sea anglerfish (Ceratias holboelli), can reach about 4 feet (120 centimeters). However, the majority of deep-sea forms fall into a smaller range of 1 to 7 inches (2 to 18 centimeters) in length.
Sexual Dimorphism and Body Size
Within the deep-sea anglerfish, body size is dictated not only by species but also by sex, a phenomenon known as extreme sexual dimorphism. In many deep-sea species, the female is the massive hunter, possessing the bioluminescent lure and a robust body. The male, conversely, is dramatically smaller, often only a fraction of the female’s size. This size disparity is a reproductive adaptation to the scarcity of mates in the deep ocean environment.
Once a diminutive male finds a female in the pitch-black depths, he uses specialized teeth to latch onto her body. In several families, this attachment becomes permanent, with the male’s mouth fusing to the female’s skin, and their circulatory systems merging. This parasitic attachment reduces the male to a mere sperm-producing organ, dependent on the female for all his nutritional needs. The size difference can be staggering, with the female being up to 60 times the length and half a million times the weight of her mate.
The smallest sexually mature male anglerfish, from the species Photocorynus spiniceps, measures a mere 0.24 inches (6.2 millimeters) long. This tiny male is permanently attached to a female who is about 1.8 inches (46 millimeters) in length. This parasitic strategy ensures the female has a constant supply of sperm available for spawning, making her the functional size reference for the species. The male’s existence is entirely devoted to reproduction, lacking a lure or the ability to hunt for himself.
Providing Scale
To visualize the immense range in anglerfish size, it is helpful to compare them to everyday objects. The smallest mature male anglerfish, measuring just over 6 millimeters, is comparable to a grain of rice or a small pea. A typical deep-sea female, measuring around a foot long, is roughly the size of a standard ruler.
The largest anglerfish, the European Monkfish, can reach 6.6 feet, making it longer than the average adult human is tall. These heavy, shallow-water species can weigh over 100 pounds, comparable to an adult human. This extreme contrast highlights the biological diversity within the order Lophiiformes, spanning a size range from creatures smaller than a thumbnail to those longer than a person.