Marine Vertebrates

CHORDATA - Animals with a stiffening notochord, a tubular dorsal nervous system with gill slits behind the oral cavity at some time in their development. There are three sub-phyla, two that lose their notochord as they develop into an adult and the other that develops an endoskeleton retaining its notochord (Vertebrata).

Vertebrata includes seven classes that have an endoskeleton and a spinal cord.

  1. Agnatha - Jawless fishes including the lamprey and hagfishes. Hagfish have an odorous slime over their bodies which helps protect them from predators. They rasp into their prey with their rough tongue. Lampreys burrow into their prey such as bony fish but they have also been found feeding on whales and porpoises.

    The hagfish is usually found in deep water. No researcher has ever found a fertilied hagfish egg. For that reason in the mid-19th Century, the Royal Danish Academy of Sciences and Letters offered a gold bar prize for anyone who could unravel the hagfish breeding behaviour. The prize has never been given.

    The hagfish frequently enters its prey through its mouth or digestive system. It literally eats its prey from the inside out. Fisherman sometimes haul a plump fish on the deck only to see a hagfish slither out of its prey's mouth.

    As a defense the hagfish exudes a viscous slime which helps it to slip away from its predators. For this reason its is sometimes called a "slimy eel" although it is not an eel.



  2. Chondrichthyes - Fishes with a cartilaginous skeleton including sharks, skates and rays. These organisms have no air bladder so they have negative buoyancy which means that they have to keep swimming or they will sink.

    Skates and rays are smooth skinned while sharks have rough skin. Some rays have a poisonous barb on a tail while others can produce an electric shock capable of stunning its prey or a human diver.

    Most sharks, 80%, are less than six feet and only a few of the remaining 20% are aggressive toward man. The one that is most dangerous is the Great White Shark (actually grayish brown or blue above and creamy on their bottom) with a length of 23 feet and weigh 3000 pounds. The mako is also a dangerous species reaching lengths of 13 feet.

    These and other aggressive species of shark are attracted by vibrations in the water sensed by lines along the sides of their bodies. Smell also helps sharks to locate prey.

    Shark teeth are slanted toward the back of the mouth allowing a shredding action on the prey. Shark teeth are a ranged in multiple rows and grow back if lost.

    Sharks are not especially intelligent and do not remember encounters with humans.



    Click here to see picture of and articles about sharks.

  3. Osteichthyes - Click here to see picture of bony fish. - Bony fish have about 27,000 plus species. 90% of all bony fish belong to the order Teleostei.

    These fish have swim bladders, independently controlled fins, the ability to communicate, the ability to camouflage, socialization abilities.

    These organisms are poikilotherms, cold blooded.

    They drink sea (salt) water and excrete salt by special glands in the gills and eliminates water by osmosis and very little in urine.

    Bony fishes sense vibrations through their lateral lines, small canals in the skin and bones around the eyes and over the head and down the sides of the fish. These canals have nerve endings.

    Fish smell and use this for a variety of activities including the return to breeding sites.

    These organisms range in size from large blue fin tuna to the smallest fish, the pygmy goby which is only 0.3 of an inch. One of the largest food-source fish, now the most sought after fish by the Japanese, is the bluefin tuna. They range in size from 300 to 1,500 pounds. Its fat-streaked belly, (toro), is a sushi delicacy and sells for $75 per portion in Japan. For that reason bluefin tuna are sold for $10 to $12 per pound. At the height of the market, which is now drastically reduced since Japan now fishes for them, a bluefin tuna was sold for $83,500, or $117 per pound.

    One of the most unique and spectacular fish in the ocean is the bluefin tuna. Bluefin tuna are unusual in that they are a warm blooded fish. For that reason they need larger amounts of oxygen and to get it they are constantly swimming to pass water rich in oxygen over their gills. They are among the fastest swimming fish in the ocean reaching speeds of 50 miles an hour. Their body structure enhances their speed. Their lateral fins actually fold into slots in their bodies giving them a sleeker body.

    Because of their their need to move constantly they also spend almost all of their time hunting for food which includes mackrel and herring among other smaller fishes. For this reason they roam the coast of North America in search of food. While they used to be found in the summer months in great abundance off Montauk Point, more recently they have not been found in that area. Instead, in 2000 they were found 50 miles south and east of Saquatucket near the BB buoy.

    There is an international organization, the International Commission for the Conservation of Tunas, which is made up of 30 nations. Based upon the Commission's quotas, the Nationa Marine Fisheries Service has set a limit on one bluefin tuna per day per fishing.

    Not only are fish populations being depleted by over-fishing in the open ocean but the over-fishing for caviar as well in spawning estuaries is a cause as well. Female Beluga sturgeon have been over-fished in their spawning grounds, the Volga River resulting in a depletion of the beluga sturgeon and five other lesser known sturgeons.

    Studies of fish populations in various parts of the ocean show a significant decline in the numbers of fish as a result of overfishing. The use of commercial fleets, improved netting techniques, and factory boats have so diminished some fish populations that they border on the extinct. The Canadian cod is an example. It has been reduced to 1% of its 1950 population. Although fishing for Canadian cod has been banned for 10 years there is little sign of its return to former population levels.

    Swordfish taken from Georges Banks had diminished to the point of almost extinction but a ban on swordfish fishing has increased the population. The return of fish populations was seen during World War II. Because of the threat of German U-boats, little or no fishing took place in the North Atlantic. The populations of fish soared.

    Studies show that in general fish that are now caught are much smaller than those caught in past because of intense fishing which does not give the population a chance to grow to maturity. Some estimate that the fishing populations have been reduced by 90% because of overfishing. When one species of fish is depleted, commerical fisherman and restuarants simply replace it with another species and the overfishing transfers to another species.

    By-kill is the death of fish that are caught in nets but are not as commercially valuable so they are discarded. This too has diminished some species of fish. Dolphins and seals are frequently caught as by-kill in gill nets and sea birds and fish other than those sought get caught on long lines as by-kill.

    Fully 90 percent of each of the world's large ocean species, including cod, halibut, tuna, swordfish and marlin, has disappeared from the world's oceans in recent decades, according to the Canadian analysis -- the first to use historical data dating to the beginning of large-scale fishing, in the 1950s.

    The new research found that fishing has become so efficient that it typically takes just 15 years to remove 80 percent or more of any species that becomes the focus of a fleet's attention. Some populations have disappeared within just a few years, belying the oceans' reputation as a refuge and resource of nearly infinite proportions.


    Click here to see the unique characteristics of marine fish.

  4. Anadromous Fish - Click here to see picture of Anadromous fish. - Anadromous fish are fish that spawn in fresh water but live most of their lives in the ocean. The more celebrated salmon is well known but, striped bass are also anadromous fish. Each spring, these fish ascend the river in which they were spawned guided, scientists believe, by chemical cues in the water they first picked up years before, when they were as big as guppies.

    Pacific salmon will only return and spawn once and die after spawing.

    North Atlantic salmon are different. They return twice to spawn. Stripped bass spawn each year in the rivers in which they were spawned. Many stripped bass in the North Atlantic spawn in the Hudson River. They swim just past the saltwater wedge that reaches up the river far north of New York City. They spawn almost exclusively in two sections of the Hudson: between Kingston and Catskill, and between Croton Point and the dam across the river at Troy.

    Striped bass are among the most fecund fish. Very few of the fry will survive. The striped bass produces more roe than even a large sturgeon. Striped bass have large mouths. They close their gill flaps and literally vacuum the smaller fish into their mouths. Striped bass will attack prey in schools and when it happens the sea looks like it is boiling with the prey trying to escape and the predators swimming close to the surface.

    Pollution in the Hudson River and over fishing has greatly reduced the striped bass population. The minimum size for a striped bass is 28 inches. Many that are caught are as long as 48 inches and can weigh 125 pounds. They can be caught by net or hook.

    Ten per cent (10%) of hooked strip bass that are returned to the ocean will die. The younger the fish, the less likely it will die. The cause of death is frequently the built-up of lactic acid in the muscles as the fish fights the hook. As lactic acid builds-up in the muscles it will begin to migrate to the blood stream where the pH of the blood will be altered and the fish will die as a result. The salinity of the water and the temperature can also play a role in the fish's death.

    Sport fishermen frequently surf cast from the beach or in the surf when the striped bass are "running", that is returning to spawn, or migrating north or south.

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    Click here to see pictures of moray eels.


    Deep Ocean Fishes



    The deep ocean is eternally dark, slightly hyper-saline 360/00, and highly pressurized. Organisms that inhabit these deep reaches of the ocean have a number and variety of adaptions that permit them to live in this inhospitable environment. They are slow moving. These organisms have a low metabolic rate which requires little food. Some of these organisms may eat only once a year. They have unique ways of capturing or obtaining food. Some have extensions of their fins and/or gills which are sensitive to the movement of prey several meters away. Some are sensitive to the smell of decaying organisms and will find the detritus and feed upon it for months. Some organisms have a large mouth with spines that point backward toward their cut. These organims simply lie on the bottom with their mouth open which small prey perceive to be a cave. Their prey will swim into the open mouth and the spines direct them to swim further into the gut of the fish.

    Deep ocean organisms are flabby, not muscular, and have no swim bladder. The exoskelton of deep ocean organisms is thin. Many of these organisms are fragile yet able to withstand the high pressures of their habitat because their internal pressure is equal to the external pressure.

    Below are pictures of deep ocean organisms that washed up on beaches after the December 2004 Indian Ocean tsunami.



    Lizard fish


    Prickly shark

    Umbrella mouth gulper


    Coffin fish


    Chimaera pup fish


    Fangtooth fish


    A deep ocean crab. Note the long spindly legs which is typical of deep ocean organisms.


    A chimaera fish.




  5. Amphibia - There are no true marine amphibians. These organisms would by osmosis lose water to the ocean and would dehydrate.

  6. Reptilia - Marine reptiles include sea turtles (green and leatherbacks), marine crocodiles, marine lizards, sea snakes (sea-krait).

    Sea snakes do not inject venom with their teeth. They capture their prey with their teeth and a neurotoxin in the saliva seeps into the wound and paralyzes the prey. These snakes have a flat tail to improve swimming. Kraits have a lung that extends the length of their body allowing them to stay under water for up to 5 hours. Sea snakes are abundant in the Indian Ocean and the Western Pacific. There are none found in the Atlantic.



    All sea turtles (and other marine organisms such as sea slugs, marine birds, fish, lobsters) use the earth's magnetic field to navigate. Although the earth's magnetic field is about 1/20,000th as strong as a magnet on your refrigerator door, it is enough for turtles to use in navigation. There are two receptors in turtles. One is an iron based receptor and the other is based upon changing light.

    Hatchlings will navigate from their birth place, a beach in Florida, to Spain and back. Turtles navigate from the coast of Mexico to Japan and back.

    The turtles use the direction and the intensity of the magnetic field to navigate. Magnetic maps are imprinted on the hatchlings who follow the map through warm, food-rich waters.




  7. Aves - Marine birds are homeotherms, warm blooded and have glands capable of eliminating the salt they ingest in sea water. They include four marine orders.

  8. Procellariiformes - Tubernoses include the albatrosses, petrels, and shearwaters. They are very efficient gliders both seeing and smelling their prey. These birds can reach speeds of 50 miles per hour and have ranges of 9,300 miles on foraging trips.

    Wandering albatrosses in the southern Indian Ocean can journey a thousand miles or more across open water in search of food and return to their small breeding island. It's a nifty feat of navigation, made even niftier by the fact that there are almost no landmarks to help - islands in the region are few and far between.

    "The lack of visual cues has led some researchers to speculate that the birds must rely on the earth's magnetic field to navigate. Such magnetic compasses are known in some other birds and animals. The idea is that if the animal always knows the direction of the magnetic field, it can use that information to find its way home.

    To test this, French and Swiss researchers outfitted wandering albatrosses on the Kerguelen Islands with satellite tracking devices that could log their locations every hour or two. To disrupt the birds' ability to perceive the earth's magnetic field, plastic tubes containing strong magnets were attached to their heads. Control birds carried nonmagnetic bars of similar weight.

    The results, reported in Proceedings B of the Royal Society, show that the secret of the albatrosses' navigational prowess remains unsolved. Both groups of birds made it safely home after foraging trips of up to 4,500 miles, and there were no significant differences between the two groups in trip duration, distance traveled or how straight a path the birds took.

    The researchers suggest the birds may use the sun, rather than the magnetic field, for navigation. Although most of the flights in the study were conducted under heavy cloud cover, enough polarized light probably gets through to allow the birds to determine the orientation of the sun." The New York Times, March 17, 2005


  9. Pelecaniformes - Pelicans, cormorants, frigate birds and boobies belong to the same order.


  10. Charadriiformes - Gulls, terns, and puffins belong to the same order.


  11. Shenisciformes - Penguins have lost their ability to fly but are excellent swimmers. They are able to dive to depths of 900 feet in search of prey. They are found in the Southern Hemisphere most frequently in the Antarctic regions although some are found in the Humboldt Current near the Galápagos Islands.

    The mating and feeding habits of penguins are the subject of many studies. The Emperor Penguin breeds in the Antarctic winter, they do not establish territory but huddle together to keep warm. Those birds in the center of the huddle are warmer than those on the outside edge. They slowly move outward to the edge to provide warmth. Male penguins frequently brood the eggs and young while the female forages for food sometimes ranging 300 miles away from the rookery.

    For decades, scientists have been attaching numbered strips to the flippers of penguins which some researchers believe may increase drag and make it harder for penguins to swim thus affecting their overall behavior.

    Dr. Michel Gauthier-Clerc of the National Center for Scientific Research in Strasbourg, France, in a five-year study of king penguins on Possession Island in the southern Indian Ocean showed that banded birds often returned to the colony later than unbanded ones, had a lower probability of breeding and produced fewer offspring.

    It appeared that the impaired swimming affects the birds on critical foraging trips which ulimately decreased their body reserves. King penguins normally increase their weight 50 percent on a three-week trip that precedes the November breeding season. If there are not enough reserves, the penguins can't engage in reproduction. Below is a king penguin rookery on South Georgia Island.



    A King Penguin rookery on Salisbury Plain on South Georgia Island.




    As awkward as penguins are on land, in the ocean they are excellent swimmers capable of diving to great depths to obtain food.

    Penguins emerging from water. They propel themselves out of the water and appear to pop out onto the sea ice.



    Semi-palimated sandpiper.


    Pectoral sandpiper


    White-rumped sandpiper.

    These Arctic birds are migratory. The migratory patterns of birds are frequently studied to determine the method of orientation used by the organism. Some organisms orient by a magnetic compass, some by a celestial compass and some by a solar compass.

    The study of these birds shows that they use a solar compass since they migrate from the Arctic to South America only in the Arctic summer. They could not use a celestial compass since there is constant sun in the summer. They would not be able to use a magnetic compass since the North Pole would give a distored magnetic field.

    The albatross is a sub-arctic bird that can hunt for food over a range of more than 1,500 miles.


    This is a picture of a piping plover which has been an endangered species since 1986.

    For this reason beach areas in and around Long Island have been protected when piping plover nests are found on them. Vehicles and pedestrians may not pass within 3,000 feet of any nesting site. This protection has resulted in an increase in the numbers of piping plover pairs. Long Island can now boast of 350 piping plover pairs.

    Piping plovers will be removed from the endangered species list when there are 2,000 pairs along the East Coast. The last count was 1,525 pairs in 2001 according to the Nature Conservancy.




    Piping plovers are shore birds weighing less than three ounces. They are named for the bell-like, plantive piping sound that they make. There are fewer than 1,500 breeding pairs on the entire Atlantic coast from Newfoundland to North Carolina. Mature birds winter in North Carolina, Florida, the Texas coast, the West Indies, and the Bahamas.


    Plovers lay their eggs in open beach areas rather than in sandy dunes.
    The eggs are speckled and blend with the sandy beach.

    An albatross returns to its nest to feed its chicks. Note the long wing span for long flight. Also, note the webbed feet for swimming when diving for food.

    An albatross that has drown on a fishing long line. Many diving birds are caught on these lines. Other marine mammals suffer a similar fate. Seals are frequently caught in gill nets and drown.


  12. Mammalia - These are homeothermic, air breathing, live birthing, and have hair at some time in their life and suckle their young from mammary glands.

    There are three orders of marine mammals. All of these have adaptations that help them to survive in a marine environment.

    They have a streamlined body; they generate body heat from a high metabolic rate and conserve heat with layers of fat and, in some cases, fur; they have a modified respiratory system allowing them to stay under water for as long as 90 minutes and to dive to great depths; they have osmotic adaptations allowing them to drink small amounts of sea water with no need for fresh water.


    Click here to see pictures of whales that can be found in waters off Long Island.

    Cetacea - Whales have two sub-orders.

  13. Odontoceti, toothed whales including the large sperm whale. The smaller orca whale or killer whale is the trained whales in aquariums. These whales find their prey by echolocation. These sounds are also thought to be capable of stunning prey. The sounds can be as loud as 229 decibels which is the same as a blasting cap. Sperm whales generate sounds as high as 260 decibels. It is not clear how these sounds are made.

    Killer whales hunt in pods. They will herd small fish by frightening them by circling the school and showing their white under belly. They herd them toward the surface where they pound the water with their tail fluke. The sound stuns the smaller fish. Killer whales kill larger prey, such as seals, by tossing them in the air. Penguins are herded into shallow water where they are easier to catch. This can be hazardous to the whales which can become grounded. Killer whale pods use different methods of hunting depending on their location. In the Indian Ocean killer whale pods wait for blue fin tuna fishing boats to hook a tuna, then they attack the tuna while it is on the line. Partially eaten tuna are frequently hauled into the fishing boats as a result of this hunting technique. Finally, there is a silent pod of killer whales that will attack dolphins but remain silent since dolphins also have echolation.




    Dolphins are mammals but they are unique in that the male dolphin has internal testicles. This is not good since the sperm cells do not develop correctly in high heat environments. The dolphins have a unique cooling system where cool water flowing over their flukes and fins cools venous flow which circulates near the testicles thus lowering the temperature to an optimum range. The same occurs in the female and the optimum temperature for gestation of the fetus occurs as a result of this circulation system.




    Dolphins surfing.

    An orca (killer) whale breaching.

    Naval ships emitting pulses of sound have been blamed for several mass beachings. Scientists surmise that sonar may disorient or scare marine mammals, causing them to surface too quickly and creating the equivalent of what divers know as the bends - when nitrogen is formed in tissue by sudden decompression, leading to hemorrhaging. Autopsies on dead, beached whales and dolhins frequently show physical damage to their ears Unfortunately, toothed whales travel in close-knit families called pods. Travelling in a pod has contributed to the deaths of some of these organisms. The pod is so close-knit that if one whale becomes injured or stranded all the others in the pod will remain with it.

    In the summer of 2002, a pod of 60 pilot whales became stranded on a beach in Dennis on Cape Cod. The residents and scientists kept the whales wet and covered with towels to prevent heat exhaustion, sunburn and dehydration. Eventually the entire pod wash freed and returned to the water only to have them return a day later. Some of the whales died and many had to be euthanized since they could not be saved.

    Strandings like this occur because of strong currents and tides and shifting sandbars. Sometimes the whales follow prey into shallow water, sometime a dying whale will beach itself and the others follow and will not leave it.

    One of the largest strandings happened in New Zealand where 300 pilot whales stranded themselves and 288 died. There have been several strandings on Cape Cod in the past.

    Species other than pilot whales have stranded themselves including killer whales, white-sided dolphins, false killer whales, and pygmyg sperm whales.

    Individual strandings of whales, dolphins and sea turtles have occurred on Long Island beaches. Many of these organisms were sick or injured. In the summer of 2002, a dead humpback whale was found on a beach. It appeared to have been hit by a ship or boat causing its death directly or through infection.



  14. Mysticeti baleen whales strain krill with interleaving triangular plates of baleen and collect as much as 6,600 pounds each day. The largest whale and mammal is the blue whale. These whales frequently communicate with each other by sounds and the humpback whale