The Pacific viperfish, Chauliodus macouni, is a predatory fish that lives in the bathyal zone or bathypelgic, ranging from 1000m-4000m and having an average temperature of 4 degrees Celsius. However, the pacific viperfish has been found in the mesopelagic region, above the bathypelagic. In daytime it can be found from 200-5000 m below the ocean surface. At night it swims up into shallower depths of less than 200m where food is more plentiful. Pacific viperfish do not have a particular fish that they mainly feed on, but they will go after crustaceans, plankton, shrimp, small fish and occasionally will catch a larger fish. The pacific viperfish is one of the nine different species that belong to the genus Chauliodus or Viperfish. The pacific viperfish tend to be the largest of the species, typically reaching lengths of up to 1 foot and are considered an example of deep-sea gigantism. The pacific viperfish is classified as one of the most ferocious deep seas fish for its size. They are iridescent dark silver-blue color in life with pale fins. They can also be a light black color with blue fins. Looking at the mouth and curvature of teeth one can easily recognize the pacific viperfish. The fangs of the pacific viper are abnormally long that its jaw is extended out, so its teeth can fit outside of its mouth. The fangs rest near the viper’s eyes. These fangs are the viper’s way of killing fish, the viper will swim at high speeds at its prey and impale them in the process. High speed collisions and force in bites have cause the viperfish to adapt to high impact. The vertebrae that is located right behind its head is used a shock absorber, very similar to an air bag. They are excellent maneuvers in areas that receive significantly less sunlight than uppermost regions. This is accredited to a protein in the rods known as Rhodopsins, composed of the transmembrane protein opsin, and a chromophore.
Hunting and feeding
According to O'Day luminescent silhouetting may aid the fish in mating, spacing themselves out as they hunt, maintaining conspecific aggregations, warning potential predators of their own formidable size, or perhaps allowing them to escape from predators by temporarily blinding them. These functions, however, remain speculative. The photophore is found on the dorsal fin of the pacific viper. The photophore uses bioluminescence to produce light to entice a victim. The prey is attracted to the flickering light like a fishing lure. Along with the extended photophore on the dorsal fin, the viperfish also carries photophores on side and underneath its body. The lights underneath provide a camouflage to fish from below. The photophore also serves as a communication tool; it is used by the viperfish to signal a mate or ward off potential rivals in the area. The pacific viper utilizes the low visibility and darkness to its advantage for hunting tactics. The pacific viper lies motionless in the darkness and waves its blinking lure over its head waiting on its meal to arrive. Their stomach is quite large, and they have low basal metabolic rates which enables them to go days without food and store up on food.
Reproduction
Little is known on pacific viperfish reproductions due to the depths it lives at. Due to darkness and limited mates it is best suited that the pacific viper externally spawn or oviparous. Females will release eggs into the water which the male will fertilize. The number of eggs and larvae produced by the female is determined by the temperature of the water and concentration of salt. Spawning is believed to occur year-round but with spikes of young larvae during January and March. When an offspring is born it is about six millimeters long. Offspring’s are expected to defend themselves until they are mature.
Parasites
As most fish species, the Pacific viperfish has several parasites. In 2018, Susumu Ohtsuka, Dhugal J. Lindsay and Kunihiko Izawa described a new genus and species of pennellidcopepod, Protosarcotretes nishikawai, from a single ovigerous female infecting a Pacific viperfish collected from the deep-waters of Suruga Bay, Japan. According to the authors, the new genus had the most plesiomorphic states in the first to fourth legs of pennellid copepods.
Captivity
Viperfish are not an endangered species, but they are preyed on by some dolphin and shark species. They are also unable to live in captivity because of the extreme pressure differences within the environment. Pacific viperfish have been recorded living from 15–40 years in their natural habitat. A few species have been captured, but only lasted a couple hours before dying.
