Marine Fish - Science with Ms. Reathaford!

Marine Fish - Science with Ms. Reathaford!

Marine Fish Marine Fish: An Introduction Fish were the first vertebrate, appearing more than 500 million years ago. The first fish are thought to have evolved from an invertebrate chordate not much different from lancelets that still inhabit the ocean. Fish soon made their presence felt and have had quite an impact on the marine environment, feeding on nearly all types of marine organisms. Fishes are also the most economically important marine organisms.

Economical Importance of Marine Fish As noted, fishes are the most economically important marine organisms because of the following: They are a vital source of protein for millions of people They are sometimes ground up for fertilizer or chicken feed Leather, glue, vitamins, and

other products are obtained from them Sportfishing Kept as pets by many An Introduction to Vertebrates Vertebrate are different from invertebrate in that they have a backbone (or vertebral column / spine) which is a dorsal row of hollow skeletal elements called vertebrae. Vertebrae are typically made of bone. Vertebrae used to enclose and protect a nerve cord (spinal cord), which

ends at a complex brain. The brain is protected by the skull, which is made of cartilage or bone. Vertebrates are characterized by a bilaterally symmetrical body and the presence of an endoskeleton. Types of Fish Fishes are the oldest and structurally the simplest of all living vertebrates. Fish are also the most abundant vertebrates in terms of both species and individuals. There are approximately 30,000 species of fish known to science, making up about half of all species of vertebrates on Earth. Most known species of fish are marine and many new species are being

added every year. There is disagreement, among scientists, regarding how to classify major groups of fish. Despite this, three groups are traditionally recognized: Jawless Fishes 2. Cartilaginous Fishes 3. Bony Fishes 1. Jawless Fish: Agnatha The most primitive fishes living today are the jawless fishes. Characteristics: Feed by suction with the aid of a round,

muscular mouth Rows of teeth within mouth Body is cylindrical and elongated Lack paired fins and scales of most fish Lack a true vertebrae, so some scientists argue if they are truly in vertebrates group Hagfishes (Slime Eels) Characteristics: Jawless fishes that feed mostly on dead or dying fish Sometimes bore into their prey and eat them from the inside out Live in burrows they dig in

muddy waters, at moderate depths in cold water Only about 20 known species Reach a maximum length of 2.6ft Skin is used to manufacture leather goods Known for attacking bait on fishing lines, nets, and traps Lampreys Characteristics: Found in most temperate regions, anadromous fishes (live in oceans most of their life, move to

freshwater to spawn) Uses teeth to create a wound on its prey, then uses tongue to rasp a hole in its victim Then attaches itself to other fishes, using buccal papilla to form a suction, and sucks their blood. It can also use the buccal tunnal to wiggle up rock faces To prevent the blood from clotting, lampreys release their own anticoagulant 30 known species

External Features: Lampreys The skin of a lamprey is smooth and slimy, lacking scales It has a symmetrical caudal fin that is tapered at the posterior end While it swims, the anterior and posterior dorsal fins keep it upright Lampreys do have muscle segments (myomeres) that can be seen through the skin

Excretory waste passes through the cloacal aperture Head Features: Lampreys There are 7 external gill slits in a lamprey, and it uses muscle contractions to draw in (relaxation) and expel (contraction) water into the gill pouches when it is attached to its prey The primary function of the gills; however, is to absorb oxygen and remove carbon dioxide from the blood The head contains a nostril, which is

not connected to either its mouth or pharynx Lampreys are capable of detecting light due to having a pineal organ The lampreys brain has olfactory and optic lobes, which are the most developed parts Internal Features: Lampreys The main component of the lamprey skeleton is the notochord, which runs along the dorsal length of the body The heart of a lamprey contains

ventricles, which pump blood through the gills and the body. Blood then enters the sinus venosus and then into the atrium, which pumps blood into the ventricles Surrounding the heart is the pericardial sac, protecting it Lampreys do not have stomachs as their diet is liquid (blood), but there is a liver to store products of digestion A lamprey does have kidneys, which remove nitrogenous waste and balances water

Cartilaginous Fishes Ancient group of fishes that includes sharks, rays, skates, and ratfishes. Cartilaginous Fish: Chondrichthyes Characteristics: Skeleton made of cartilage, which is lighter and more flexible than bone More advanced than jawless fishes Movable jaws that are usually filled with welldeveloped teeth Mouth is almost always ventral (under the head) Paired lateral fins for efficient swimming Rough, sand-paper like skin due to teeth-like placoid scales consisting of a pointed tip that is

directed backward Sharks Sharks are adapted for fast swimming and predatory feeding and are one of the most fascinating animals within the sea. Because many of them are similar to species that swam in our seas over 100 million years ago, sharks are sometimes referred to as living fossils. Shark: External Features Spindle-shaped bodies tapering from

the rounded middle to each end allows them to move easily through the water Caudal fin (tail) is well developed and powerful and is usually heterocercal (upper lobe is longer than lower lobe) which causes the shark to be driven downward as it swims Upper surface of the body features two dorsal fins, first is longer and triangular, with a large spine at both anterior ends Paired pectoral fins are large and pointed in most species

Five to 7 gill slits are behind the head and present on each side of the body Shark: Head Features Shape of head provides lift to compensate for downward thrust of caudal fin when swimming Powerful jaws have rows of numerous sharp, often triangular teeth that are embedded in a tough, fibrous membrane that covers the jaws Lost or broken teeth are replaced by another that slowly shifts forward from the row behind it as if on a conveyor belt Has an inner ear, which senses sound and

helps maintain balance Contains spiracles, which bring water into the gills when the mouth is closed Complexity allows sharks to see in color Sharks are efficient hunters because their nostrils allow them to dinstinguish which side is closest to the strongest scent (swims in that direction) 5 pair of external gill slits in most species Shark: Internal Features Possesses an oily liver, which helps with buoyancy for the shark

Bile is stored in the gallbladder, which helps break down fat in the sharks diet Also has a spleen, which produces red blood cells Intestines house the spiral valve, which increases the surface area of the intestine for larger feedings The sharks stomach contains many wrinkles (rugae) Heart allows blood flow to enter sinus venosus and then to atrium where it is pumped into the ventricles, which pump the blood to the gills and then to the body Salt is removed from the sharks body through a rectal gland Exceptions There are nearly 350 living species of sharks, but not all

conform to the typical body plan: Hammerhead Sharks: flattened heads with eyes and nostrils at the tip of bizarre lateral extensions. The head serves as a sort of rudder ad separates the eyes and nostrils to improve the sharks sensory perception. Sawsharks : extends in a long, flat dorsoventrally flattened blade armed with teeth along the edges. Thresher Sharks: upper lobe of the tail is very long, which they use to herd and stun schooling fishes when they eat

Exceptions in Size The size of a fully grown adult shark also varies: Spined Pygmy Shark: grows to no longer than 10in Whale Shark: largest of all fishes found in tropical waters around the world, may be as long as 60ft but any species longer than 40ft are rare. Despite this, they cause no harm to humans and are filter feeders Basking Shark: 50ft on some occasions, but most do not exceed 33ft. Basking sharks are also filter feeders Great White Shark: considered most dangerous shark of all, exceeding 20ft in length

Shark Habitats Sharks are found throughout the oceans at practically all depths, but they are more prevalent in tropical coastal waters. Sharks are primarily marine, but a few species travel far up rivers. Small specimens are typically found in brackish waters, in estuaries, and coastal regions. Bull Sharks Northern River Sharks

Speartooth Sharks Overfishing of Sharks Due to our appetite for shark, overfishing has become a great problem. Common Reasons of Shark Fishing: Shark meat is eaten around the world, many people eat it without knowing, as it is often illegally sold as fish or scallops Sharks are fished for their liver oil Sharks are fished for their skin, which is processed into leather or

sandpaper Sharks are fished for their fins Shark Fin Soup is a delicacy in the Orient Shark cartilage is a joint nutrient that may help in use of arthritis Overfishing of sharks has led to more stringent management of shark fishing. The number of sharks is declining across the world due to slow-growing and slow-reproducing of the animal. There has also been a ban placed on shark finning in the USA and other countries around the world. Web MD: Shark Liver Oil Overview and Information

Common Uses How it Works Shark liver oil is used to make medicine. It is taken from the livers of three species of shark: the deep sea shark, the dogfish shark, and the basking shark to treat leukemia and other cancers

to prevent radiation illness from cancer X-ray therapy to prevent the common cold, flu, and swine flu to boost the bodys immune system To increase white cell counts during treatment

Shark liver oil contains chemicals that might have activity against cancer or cancer treatment related side effects The liver makes up about 25% of the total body weight of these sharks Rays and Skates There are 450-550 species of rays and skates in the marine world.

Characteristics: Dorsoventrally flattened bodies Demersal (live on bottom of ocean, for most part) Gill slits (5 pairs) are on the underside of the body rather than on sides Pectoral fins are flat and expanded, like wings, and are fused with the head Eyes are on top of the head Exceptions: Not all rays are demersal. Eagle rays, the manta, and devil rays fly through water using ther pectoral fins like wings. Each of these have been observed leaping out of the water Tropical Sawfish

Characteristics: Look like sawsharks but have ventral gill slits (so grouped with rays) Feed by swimming through schools of fish and swinging blades back and forth to disable prey Known to grow up to 36ft long Stingrays Characteristics: Whip-like tail equipped with stinging

spines at the base for defense Poison glands produce venom causing wounds to anyone who steps on them Many abdominal wounds result in death to those handling them Cover themselves completely with sand, nearly invisible Feed on clams, crabs, small fishes, and other animals in sediment Lift sediment with fins to expose prey and then crush them with teeth modified into grinding plates Give birth to live young

Electric Rays and Skates Electric Rays Skates Characteristics: Possess special organs that produce electricity on each side of their head Deliver shocks to prey of up to 200 volts Ancient Greeks and Romans once used electric

rays to cure headaches and other ailments the original shock Characteristics: Similar to rays in appearance and feeding habits Lack a whip-like tail and stinging spines Some have electric organs Lay egg cases Abundant, are fished for food in some parts of the

world Bullseye Electric Ray Skate Ratfishes About 30 species of ratfishes are grouped separately due to their unique characteristics: Strange looking, mostly

deep-water Have only one pair of gill slits, covered by a flap of skin Long rat-like tails Feed on bottom dwelling crustaceans and molluscs Bony Fishes The great majority of fishes are bony fishes. As the name implies, they have a skeleton made at least partially of bone. There are approximately 23,000 species of bony fishes about 96% of all fishes and almost half of all

vertebrates with 75-100 new species being named every year. A little more than half of all bony fishes live in the ocean, where they are the dominant vertebrates. All land vertebrates are said to have evolved from Bony Fishes: Osteichthyes Characteristics: The composition of the skeleton is not the only distinguishing feature of bony fishes Usually have cycloid or ctenoid scales (thin, flexible, and overlapping). Cycloid scales are smooth Ctenoid scales have many tiny spines along exposed borders

Scales are made of bone and covered by a thin layer of skin and protective mucus layer Scales have growth rings, in which you can count to determine the age of the fish Some bony fishes lack scales altogether Operculum (gill cover) that protects gills and helps pump water over gills while fish is stationary Bony Fishes: Fins Characteristics: Upper and lower lobes of the tail (caudal fin) are the same

size (homocercal) Fins consist of thin membranes supported by bony spines (fin rays) that are used for protection Some fin rays are flexible and used for propulsion and manuevering Fin rays help a fish hover in one location Dorsal fins help the fish remain upright in the water while swimming

Bony Fishes: Head Characteristics: Bony fish have large eyes, with large pupils, that help it see in dim underwater environments Nostril openings lead to nasal cavities Terminal mouth (located at anterior end) Jaws with much more freedom and movement than other groups of fish Protrusible jaw (can be projected outward from the mouth) with attached teeth on both jaws Teeth are replaced, but do not move

forward as other groups of fish Bony fish often swallow their food whole, although they have teeth Bony Fishes: Internal Structure Characteristics: Presence of a swim bladder (gas-filled sac) just above the stomach and intestines to provide bouyancy Swim bladder compensates for heavy bony skeleton Oviparous (eggs are fertilized and develop externally) Ovoviviparous (fertilized internally and young

are live at birth Liver to regulate glucose levels in blood Stomach divided into two parts: cardiac and pyloric Food moves from stomach to intestines through the pylorus Spleen to produce white blood cells Pancreas to produce enzymes to help digestion and produce insulin Kidneys function based on habitat: freshwater remove excess water / saltwater conserve water Bony Fishes: Habitat Bony fishes are extraordinarily diverse in shape,

size, color, feeding habits, reproductive patterns, and behavior. Due to this, they have had to adapt to nearly every type of marine environment. Biology of Fishes Ichthyology: The scientific study of fishes Body Shape The body shape of a fish is directly related to its lifestyle: Fast swimmers have a streamlined body shape that helps them move through water (sharks, tunas, mackerels, marlins) Leisurely swimmers (snappers, butterfly fishes) have laterally compressed bodies that are efficient enough for fast bursts of

swimming to escape predators or capture prey Demersal fishes (rays, skates) are dorsoventrally flattened Flat fishes (flounders, halibuts) are flat and adapted to bottom living, but bodies are laterally compressed Elongated bodies are characteristic of eels to allow life in narrow spaces or among vegetation Some are exceptions to basic shapes (seahorses, trunkfishes) based on their needs and habitat Benefits of Body Shape Body shapes can be beneficial, regardless of the marine habitat. They are most useful for

camouflage and concealment Pipefishes live among eel grass, in which they resemble Blennies have irregular growths on their head, which resembles seaweed Stonefishes bodies resemble a rock so closely that it is almost invisible to prey and humans! (Unfortunately, the shallow-water fish possesses the most potent venom and is excruciatingly painful and potentially fatal if

stepped on). Coloration Some bony fishes use color for camouflage, but some are the most brightly colored animals in the sea like displayed in the tropical region. Coloration is found in special cells in the skin called chromatophores. Chromatophores are irregularly shaped and have branches radiating from the center. The amazing colors results from a combination of chromatophores with varying amounts of pigments. Some fishes can change color by contracting and expanding the pigment in chromatophores. Fishes may also have structural colors that result from reflecting

certain colors of light. Most structural colors come from a sequence of crystals that act like tiny mirrors. These crystals are called iridophores. Do Colors Mean Anything? Colors can tell a lot about fishes: Some change colors with their mood or reproductive condition Some use color to advertise they are dangerous, poisonous, or taste bad (warning coloration) Some blend with the environment to deceive predators or prey (cryptic coloration) Some use the presence of a color stripe, bar, or spot to help break up the outline of the fish (disruptive

coloration) Some use color as a disguise in open-water, for concealment (countershading) by having a lighter belly than back Locomotion Swimming is a major part of the life of fishes. They swim to obtain food, to escape from predators, and to find mates. Some fish also swim to flush their gills with water to obtain oxygen. Most fishes swim in a rhythmic side-to-side motion of the body or tail. They form S-shaped waves of contractions from their head to tail and push against the water to force the body forward.

Rhythmic contractions are produced by bands of muscle called myomeres, which run along the sides of the body. The myomeres are attached to the backbone for support and make up a large percentage of the body weight of a fish. Swim Bladders Swim bladders provide bouyancy in bony fishes. Fish who do not have a swim bladder tend to sink so they must compensate with fins. For instance, the shark has large, stiff pectoral fins that provide lift like the wings of a plane. In addition, sharks have liver oil to provide some bouyancy because it is less dense than water

Rays and skates use their pectoral fins as their main source of lift, like wings of a bird Maneuverability Because bony fish have swim bladders to provide bouyancy, they can use their pectoral fins for other purposes. Hovering in one location Swim backwards (sharks cannot do this) Steer and provide stability Turn, balance, and brake Gliding through the air (flying fishes) Crawling or resting on the bottom (gobies) Attaching to rocks (clingfishes)

Attaching to sharks (sharksucker) Flying Fish Clingfish Sharksucker Catalina Goby Feeding: Cartilaginous Fishes Most sharks are carnivores, but in contrast to typical carnivores who capture smaller prey sharks feed by

taking bites from prey larger than themselves. Because of this, almost anything can be found in a sharks stomach Several species are filter feeders, such as the whale shark, the manta, and devil rays. These fish filter water with gill rakers (slender projections on the inner surface), which determines the size of food captured. They primarily feed on squid, schooling fish and plankton. They are also known to swim leisurely with their mouths open, taking in everything they can.

Feeding: Bony Fishes Bony fish are diverse in the way they feed: 1. Carnivorous Capture their prey with well-developed teeth to grasp and hold them before they swallow them whole 2. Grazers Front teeth are fused to form a beak-like structure to scrape off food 3. Plankton Feeders Filter plankton with gill rakers, typically straining food with their large mouths open

Most abundant fishes in the ocean Important food source for carnivorous fishes Behavior Nearly all aspects of the lives of fishes involve complex behavior: to adapt to light and currents to find food and shelter to avoid predators Territoriality Many marine fishes do not reside in any particular area; however, some are known to establish territories in which they defend against intruders. Reasons for Territories:

Territories only during reproduction Permanent territories that they use for feeding Permanent territories used for resting and shelter Fishes defend territories individually or in male-female pairs and often times, territories are shared with other organisms through division of subterritories. It is believed that fish often guard territories to ensure they have enough food and other resources and they are therefore crowded environments where resources are likely in short supply. Sometimes, fish are known to fiercely defend their territories, often attacking other fishes or divers in their space.

Defending Territories Fishes use a variety of aggressive behaviors to defend their territories: Bluffing raising fins, opening mouths, rapid darting about (actual fights are rare) Sound production grinding teeth, rubbing bones or fin spines, or drumming (pulling muscles on the swim bladder to amplify sounds) Schooling Many fishes form well defined groups (schools) that function as coordinated units although there are no leaders

Characteristics: Some school throughout their lives, but adult schools are most common with around 4000 species Schools can be huge (Atlantic Herring) Members of a school are generally the same size Fishes within a school keep a constant distance between themselves, turning, stopping, and starting in nearly perfect unison Vision plays an important role in schools, although some blinded fish can school through use of their lateral line and senses as a means of keeping track of one another. Why Do Fishes School?

There is no single reason that fishes school, but some are detailed below: To provide protection against predation (strength in numbers) To confuse predators (some will become confused when the school circles the predator or splits into several groups) It is difficult for the predator to pick just one when they are circling, darting, and shifting in a group Increases the swimming efficiency of the fish because the fish in front reduce water resistance for those behind them In some species, schooling is advantageous for feeding

and mating Migrations Another fascinating aspect of the behavior of marine fishes is migration (mass movement from one place to another once a day, once a year, or once in a lifetime). Many open-water fishes migrate up and down the water column every day; however, the most spectacular migrations are the transoceanic journeys made by tunas, salmon, and other fishes. Although we do not fully understand reasons why fishes migrate, we know that they are connected to meeting the needs of feeding and reproduction.

Migration for Feeding Recaptures of tagged fish have provided information on how far, how fast, and when tunas migrate. Tunas have been known to migrate long distances to feed in temperate water (Skipjack Tuna) Migration for Reproduction

Anadromous fishes spend their lives at sea, but move to freshwater for reproduction. The most well-known anadromous fish is the salmon. Characteristics of Migration: Use chemical memory to find their home stream by recognizing smells of the stream and streams along the way Do not feed in freshwater, live on stored fat Kidneys are able to adapt to

change from saltwater to freshwater Basic Reproduction Reproduction in fishes requires a number of adaptations of the reproductive system and the behavior that brings the two sexes together to ensure success. Timing is essential, potential mates must get together at the right time to breed. Many will congregate in breeding grounds while some come only during breeding season. Many fishes will stop feeding during breeding season in order to put all focus on reproduction. Courtship is also a necessary component of reproduction, which is a series of behaviors that are displayed to attract mates. These

involve an exchange of dances, special postures, changing colors, or swimming upside down. Each species has its own unique behavior, which is thought to keep members from mistakenly mating with the wrong species. Mandarin Fishes Courting Rituals Mandarin females gather in groups of 4-5 in one location each day. Males frequent the area, performing dances to attract them. Once a female selects a male (larger males are favored) they spawn by the

female resting on his pelvic fin. The pair slowly rises about three feet above the coral reef, where they release a cloud of eggs and sperm. Smaller males, because not often selected, will streak the area by rushing up to the mating couple and releasing their own sperm in hopes of fertilization.

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