Sea Fish

     Deep sea fish is the term that is used to describe fish that live below the photic zone of the ocean.  The fish that we will discuss today include the lanternfish, flashlight fish, cookiecutter shark, bristlemouths, anglerfish, and viperfish. 

     The photic zone is a few hundred meters below the water.  This is a very hostile environment.  There is little known about these fish because when they are captured and put in captivity, they typically die.  They are among some of the most elusive and the strangest of all creatures on earth.  Many of these deep sea fish are bioluminescent, which means they have very large eyes that have been adapted to the dark.  Some of them have long feelers that assist them to locate prey or attract mates in the ocean which is pitch black at that level.  The deep sea angler fish has a long fishing rod like adaptation that goes out from its face.  On the end of it is a bioluminescent piece of skin that will wriggle in order to lure prey. 

     Most of these fish will rely on organic matter that sinks down to the bottom from higher levels.  The deep sea is less productive than shallower areas, and this means that deep see fish tend to be smaller and have bigger guts and bigger mouths.  Additionally, the farther down a fish lives in the ocean, the more jelly-like its flesh seems to be and it has less bone structure.  This makes the deep sea fish slower and not as agile as fish that live in shallower waters. 

Lanternfish

     The lanternfish is a tiny and deep sea fish from the family Myctophidae.  Lanternfish actually account for up to 65% of all deep sea fish biomass, and they are among the most widely distributed and diverse of all vertebrates. 

     Lanternfish normally have a very thin compressed body that has silvery and small scales, a big blunty rounded head, and large round lateral eyes.  Their mouth has jaws that are closely set with multiple rows of little teeth.  The fins of the lanternfish are normally small, and they have one high dorsal fin.  They also have a forked caudal fin and an adipose fin.  The anal fin has a cartilaginous plate at its base, an it is slightly behind the rear portion of the dorsal fin.  The pectoral fins, which are usually with eight rays are large and well developed or even small or absent in some of the species.  Most lanternfish will have a gas bladder.  The lanternfish is normally small from about two centimeters to thirty centimeters in length.  The shallower living species tend to be an iridescent blue to silver or green, but deeper living species are usually dark brown to black in color. 

Flashlight Fish

     The flashlight fish are from the Anomalopidae family of fish.  This fish lives in tropical water around the world.  Some species will shift to shallow waters or to coral during the nighttime, but otherwise will stay in the deep water.  They are usually about 14 centimeters in length as an adult, but there are some species that will grow to twice this size.  The flashlight fish will fed on small crustaceans in the ocean.  Flashlight fish have large bioluminescent organs that are found beneath their eyes and they have luminous red bacteria.  The different species of flashlight fish have different methods of shielding light to escape from their predators.  The light they have is used for communication as well as to attract their prey. 

Cookiecutter Shark

     The cookiecutter shark is rarely seen by humans.  They are small, only reaching about 50 cm. or 20 inches with a cigar shape to their body.  They have rather large eyes and green pupils.  Their teeth are prominent on their lower jaw, and these teeth are utilized for feeding.  The upper jaw has small teeth.  The cookiecutter shark also has very fleshy lips.  There are two small dorsal fins on the cookiecutter shark that are near the tail.  The bottom of the shark is bioluminescent, and it usually glows a pale blue green color that will camouflage the background light of the ocean's surface.  This fish has a tiny non-luminescent patch that seems black, which tricks the prey of this shark.  The smaller predatory fish believe that the shark is smaller than it is, and when the predatory fish tries to strike at the shark, the cookiecutter shark will strike back at the predator, and it is the one rewarded with the meal. 

     The cookie cutter shark got its name form how it removes a section of flesh and skin from large fish and cetaceans.  It is possible that the shark attaches to its larger prey with its fleshy suctorial lips and modified pharynx.  Then it will rotate its own body in order to get a round cut.  It is for this reason that the cookie cutter shark is considered to be a parasite, and one of its hosts is the Megamouth shark.  The cookie cutter shark can also be found in wide open waters and in the deep sea too.  The diet of the cookie cutter shark is mostly skin, flesh, and blubber.  The fish is thought to be low in calcium, so it will eat its own worn teeth at some point and digest them for calcium and then replace its teeth with new ones. 

Bristlemouths, Lightfishes, and Anglemouths

     Bristlemouths, lightfishes, and anglemouths are a small family of fish that has 32 species.  These fish are primarily found in the Indian Ocean, Pacific Ocean, and Atlantic Ocean.  They have rather elongated bodies that are from two centimeters to 30 centimeters in length.  There are a number of green or red light producing photophores that are on the undersides of their bodies or their heads.  The name "bristlemouth" comes from their bristle like teeth that are of equal sizes.  The fish is normally black in color so they can blend into the darkness of the deep ocean and escape their prey. 

Anglerfish

      Anglerfish are bony fish that have a bony growth that protrudes from their head and looks a little like a fishing pole.  Some anglerfish live in the open water, some live on the bottom of the ocean, some live in the deep sea, and others live on the continental shelf. 

     The fish are named because of their predation.  These fish have three long filaments that protrude from the middle of their heads.  These are actually the three first spines from their anterior dorsal fin.  The first spine sprouts from above the eyes of the fish and ends in a growth of flesh that is at the tip of the spine.  The spine moves in all directions and the esca can be wiggled in order to look like a prey animal.  It acts as bait in order to lure other predators to come close enough to the anglerfish in order to be able to eat them whole.  The jaws of the anglerfish are actually triggered in automatic reflex when they come in contact with this tentacle.

     Some of the deep sea anglerfish that live in the aphotic zone will emit light in order to attract prey to them.  The bioluminescence that occurs is a result of the symbiolis that occurs with the bacteria that enters the esca of the fish from the seawater through tiny vents.  In the esca they are able to multiply until their density is tight enough that the glow that is emitted is rather bright. 

     In most of these species, the mouth will extend all the way around the circumference of the head.  Both jaws have bands of long pointed teeth.  These pointy teeth are inclined in an inward direction, and they can be depressed so that an object can slide towards the stomach easily.  This fish has the ability to distend its jaw and stomach to an enormous size; in fact, it can swallow prey that is two times as large as its own body. 

     Some of the bottom dwelling anglerfish have pectoral fins that are arm-like and allow it to walk along the floor of the ocean.  The ventral and pectoral fins can perform the job of feet, which allow the fish to walk along the bottom of the sea.  This allows it to hide in the sand or seaweed.  Around its head and body is skin that has fringed appendages that look like short sections of seaweed.  Combine this with its ability to modify its coloring to its surroundings, and you have a great combination for both hiding and finding prey. 

     The reproduction of anglerfish is odd.  Finding a mate is difficult in the deep ocean.  The scientists who first began to capture certioid anglerfish saw that all the specimens were females.  All of these females were small and had what looked like parasites attached to their bodies.  The parasites were not parasites, but the remainder of male ceratioids.  When the males are born, they have developed olfactory organs that enable them to detect scents in the water.  The male's digestive system allows them to smell scents in the water.  When the male is mature, its digestive system degenerates, and he is unable to feed independently.  This means that he needs to find a female anglerfish in order to keep from dying.  When he finds his female, he will bite into her skin, and this releases an enzyme that will digest the skin of his mouth and also her body.  This will fuse the pair to a blood-vessel level.  The male atrophies to a pair of gonads, and this releases sperm as a response to the hormones in the bloodstream of the female, which will indicate the release of the egg.  Therefore when the female is ready to spawn, she will have a mate available.  The spawn of the fish is in the form of  a sheet of gelatinous material that is two or three feet wide and twenty-five to thirty feet long.  The eggs are in one layer and each is in its own cavity.  In the sea, the spawn is free.  The larvae swim free and have the pelvic fins elongated.  This form of reproduction and egg sheet is very rare. 

Viperfish

     A viperfish is a deepwater fish that has long teeth like needles and hinged lower jaws.  These fish grow to about 30 to 60 centimeters.  They tend to stay near lower depths in the ocean in the daytime and then shallower areas at night.  The viperfish usually stay in waters that are temperate or tropical.  It is considered to be a very fierce predator in the deep portions of the sea and is believed to attack its prey when it lures the victim with its organ that produces light.  This organ is on the end of its dorsal spine and is called a Photophore.  It will flash the light on and off while it is also moving its dorsal spine like a fishing rod and holding still in the water.  It uses its voluntary light producing organ to communicate to its rivals and its mates. 

    The color of the viperfish may be black, silver, or green.  It has fang-like teeth which will immobilize its prey.  It is able to curve its teeth behind its head.  It has an ability to absorb the shock from its attack by the first vertebra behind its head.  This fish has the ability go for a long time with no food or little food.  It is believed that viperfish can live for 15 to 30 years, but in captivity, they usually live only a minimum of just a few hours.  Some dolphins and sharks will prey on viperfish.