Nutrition in Bony Fishes, (Osteichthyes)
Kingdom: __________
Phylum: ___________
Subphylum: _____________
Class:______________
Three CLASSES of fish
1.Agnathan: Jawless fish, *Hagfish, Lamprey
Label the following parts
below:
Anus
Liver
Pyloric cecum
Esophagus
Stomach
Gall Bladder
Teeth
Intestine
2.Chondrichthyes: Cartilaginous Fish, *Sharks, Rays, Skates
3.Osteichthyes: Bony Fish, * clownfish, Eel, Trout, Marlin
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Fish are aquatic vertebrates that are typically _____________ (cold-blooded)
Covered with scales
Has a Gill cover called an _____________
Minimal Protective ____________, nonselective defense against
____________
 Multiple sets of paired fins and unpaired fins
The digestive systems of fish are very similar. All have a mouth, esophagus (throat), and areas for
the absorption of food components (fore and midgut) and compaction of indigestible waste
material (hindgut). In adaptation to diet, the major differences are seen in the structure of
the mouth and the teeth, the gill rakers, the pharynx, the stomach (if present) and in the
length of the intestine. In carnivorous fish or those with a meat-orientated omnivorous diet there
is a definite stomach (foregut), herbivorous or plant-orientated omnivores have no stomach but
rely on a much extended midgut area.
Additionally carnivorous fish have extensions to
the upper part of the midgut known as pyloric
caecae.
Two other internal organs are associated with
digestion, namely the liver and the gall bladder,
located anteriorly to the stomach or anterior
section of the midgut.
Teeth: hard organ pointed backwards used to grasp and rarely shred food.
Mouth space leading to the
Esophagus (pharynx) part of the digestive tract connecting the mouth to the
stomach.
Stomach: part of the digestive tract between the esophagus and the intestine
Containing Strong Digestive Juices. Just behind the Stomach where it meets the
Intestine there are digestive glands called caeca
Pyloric cecum (caeca): sends secretions into the intestine. (enzymes)
Liver: digestive gland that produces bile an emulsifier
Gall bladder: small sac stores the bile, when needed it enters the intestine through a
common duct.
Intestine: last part of the digestive tract. Digestion is completed here. All digested
end products are absorbed directly into the circulatory system.
Anus: end of the digestive tract. Egestion
SMALL PARTICLES: Tiny particles of food are strained by long projections of gills
called gill rakers, as the particles are carried in the water passing over the gills.
Teachers Notes
Internal anatomy of a bony fish: finned vertebrate animal with skin covered with
scales. It lives in water and is usually oviparous.
Brain: seat of the mental faculties of a fish.
Esophagus: part of the digestive tract connecting the mouth to the stomach.
Dorsal aorta: vessel in the back that carries blood from the heart to the organs.
Stomach: part of the digestive tract between the esophagus and the intestine.
Contains Strong Digestive Juices
Air bladder: pocket in which urine collects.
Spinal cord: part of the nervous system that connects the brain to all other parts of a
fish.
Kidney: blood-purifying organ.
Urinary orifice: opening for eliminating urine.
Genital Orifice: opening related to the genital organs.
Anus: end of the digestive tract.
Gonad: hormone-secreting sexual gland of a fish.
Intestine: last part of the digestive tract.
Pyloric cecum: cul-de-sac related to the intestine.
Gall bladder: small sac containing the bile.
Liver: bile-producing digestive gland.
Heart: blood-pumping organ.
Gills: respiratory organ of a fish.
Tooth: hard organ of a fish used to shred food.
Eye: sight organ of a fish.
Olfactory bulb: bulging part of the smell organ of smell of a fish.
Anatomy and Physiology
A. Skeletal system.
1 . The skeleton of bony fishes is made of bone and cartilage.
2. The skeleton of a bony fish gives structure, provides protection, assists in leverage, and is a
site of red blood cell production.
3. Bony fishes have skeletons that are almost completely calcified. The vertebral column,
cranium, jaw, ribs, and intramuscular bones make up the bony fish skeleton.
The vertebral column, cranium, jaw, ribs, and intramuscular bones make up the bony fish skeleton.
B. Muscular system.
1 Tail and trunk muscles.
a. The muscles of the tail and trunk consist of a series of muscle blocks called
myotomes. The myotomes usually resemble the letter "W" tipped at a 900' angle.
b. The myotomes are separated by connective tissue called myosepta.
c. The horizontal septum separates the myotomes into dorsal (or epaxial) myotomes
and ventral (or hypaxial) myotomes.
Muscle blocks called myotomes are separated by connective tissue called myosepta.
2. Jaw muscles.
Jaw muscles usually consist of adductor muscles that close the jaw and abductor muscles that
open the jaw.
3. Fin muscles.
The fin muscles consist of abductor and adductor muscles that move the fins away from and
close to the body, and erector muscles that provide stability and flexibility in the fins.
C. Nervous system.
1 . The nervous system of fishes is poorly developed compared to that of higher vertebrates.
2. A bony fish's brain is divided into three sections: the forebrain, the midbrain, and the
hindbrain.
a. The forebrain is responsible for the bony fish's ability to smell. Bony fishes that
have a good sense of smell, such as eels, have an enlarged forebrain (Bond,1979).
b. The midbrain is responsible for vision, learning, and motor responses. Blind bony
fishes, such as blind cavefishes (family Amblyopsidae), have a reduced midbrain
(Bond, 1979).
c. The hindbrain contains the medulla oblongala and cerebellum, which coordinates
movement, muscle tone, and balance. Fast-swimming bony fishes usually have an
enlarged hindbrain (Bond, 1979).
3. The spinal cord and a matrix of nerves serve the rest of the body.
D. Cardiovascular system.
1 . Bony fishes have a heart with two chambers: the atrium and the
ventricle. The venous side of the heart is preceded by an enlarged
chamber called the sinus venosus. The arterial side of the heart is followed by a thickened
muscular cavity called the bulbus arteriosus.
a. The sinus venosus receives unoxygenated blood from the body. A valve at the end
of the sinus venosus opens into the atrium.
b. The atrium has thick, muscular walls. The atrium receives unoxygenated blood and
pumps it into the ventricle.
c. The ventricle is the largest and most muscular chamber of the heart. When the
ventricle fills with blood it constricts and forces the blood through the bulbus
arteriosus.
d. The bulbus arteriosus is a valve or series of valves that control blood flow out of the
ventricle and into the ventral aorta. Blood passes through the bulbus arteriosus to the
ventral aorta. From the ventral aorta, blood flows to the gill filaments, where it is
oxygenated.
e. The spleen, kidney, and bones are sites of red blood cell production.
2. Oxygenated blood flows from the gill filaments to the organs of the head and body. A
complex system of arteries, veins, and capillaries circulates blood through the body.
3. Some tunas (family Scombridae, tribe Thunnini) maintain a body temperature several
degrees higher than that of the surrounding water. This heat is due to the modified circulatory
system associated with the red muscle.
a. As red muscle functions, it generates heat. Muscle-generated heat warms the blood
circulating through the red muscle, which then travels back to the heart through veins.
Thus, blood returning to the heart from the muscle is warmer than blood traveling
from the heart to the muscle.
b. Due to the nearness of arteries and veins, heat passes from warmer veins to cooler
arteries within the fish's body, rather than dissipating to the cooler environment. This
modified circulatory system retains heat in the red muscle.
c. A higher body temperature is an adaptive advantage in that it provides extra power
for high-speed swimming.
d. A similar modified circulatory system warms the brain and eye of some species of
tunas (family Scombridae, tribe Thunnini) and billfishes (family lstiophoridae).
E. Digestive system.
1 . The esophagus in bony fishes is short and expandable so that large objects can be
swallowed. The esophagus walls are layered with muscle.
2. Most species of bony fishes have a stomach. Usually the stomach is a bent muscular tube in
a "U" or "V" shape. Gastric glands release substances that break down the food to prepare it
for digestion.
3. At the end of the stomach, many bony fishes have blind sacs called pyloric caeca. Although
the exact function of the pyloric caeca is unknown, it probably functions both in digestion and
absorption of food.
4. The pancreas secretes enzymes into the intestine for digestion.
5. The intestine is where the majority of food absorption takes place. The length of the
intestine in bony fishes varies greatly. Herbivorous bony fishes generally have long, coiled
intestines, and carnivorous bony fishes have short intestines.
6. The digestive system terminates at the anus.
F. Respiratory system.
1 . Water enters the gill chamber through the mouth. A bony fish can remain motionless and
breathe by pumping water over its gills by opening and closing its mouth.
2. Blood in the gill filaments absorbs oxygen from the incoming water.
3. Water exits through the gill openings located under the operculum.
4. Lungfish must return to the surface to breathe air. A lungfish swallows air to fill up an air
sac or "lung." This lung is surrounded by veins that bring blood to be oxygenated. Its gills
alone can't keep a lungfish supplied with enough oxygen to live. Other species such as tarpon
(family Elopidae) can gulp air at the surface to supplement their oxygen demand.
5. Some species of bony fishes can absorb considerable amounts of oxygen through their skin
(Bond, 1979).
G. Swim bladder.
1 . Many species of bony fishes have a gas-filled bladder called a swim bladder.
2. The swim bladder originally developed as an organ of respiration, as evidenced by the
"lung" of the lungfishes.
3. In modern bony fishes that possess a swim bladder, the organ serves principally in
maintaining neutral buoyancy. 4. In some fishes the swim bladder has adapted to function as a
sound amplifier.
H. Osmoregulation.
1. Both marine and freshwater fishes must regulate the movement of water across their body
surfaces.
2. The tissues of marine fishes are less salty than the surrounding water.
a. Water is continually leaving the body of a marine fish through its skin and gills.
b. To keep from becoming dehydrated, a marine fish drinks large amounts of water
and produces a small amount of concentrated urine. In addition, its gills are adapted to
secrete salt.
3. The tissues of a freshwater fish are saltier than its surrounding environment.
a. Water is continually entering the body of a freshwater fish through its skin and gills.
b. Freshwater fishes do not drink water, and they produce large amounts of dilute
urine.
Longevity and Causes of Death
A. Longevity.
1. Longevity for most bony fish species is unknown. Most species probably live no longer
than about 12 to 20 years.
2. In aquariums, some species of bony fishes have lived more than 50 years. Koi (Cyprinus
carpio), have been known to live as long as 100 years, and large groupers at Sea World of
California have lived in park aquariums for 25 years and are estimated to be about 30 years
old.
3. Large species generally have a longer lifespan than smaller species.
B. Aging studies.
1 . Growth rings are periodically deposited on the scales, vertebrae, and earstones of many
species of bony fishes. Experts can stain these hard body parts, examine them for growth
rings, and estimate the age of the fish.
2. Examining the scales, vertebrae, or earstones of known-age fishes after their death enables
researchers to compare the estimated age (based on growth rings) with the fish's known age.
3. In some species, tagging and releasing fish can help produce information about growth
rates. A tagged fish can be measured again when it is recaptured. Researchers correlate the
measurements with the number of years since recapture and calculate a yearly growth rate.
C. Predation.
1. Depending on the species, bony fishes have a wide variety of predators, including other
fishes, birds, reptiles, amphibians, mammals, and various invertebrates.
2. Small bony fishes have a large variety of predators. Large bony fishes have fewer
predators.
3. Many bony fishes will eat members of their own species.
D. Human interaction.
1. Commercial fishing.
a. More than I 00 million metric tons of bony fishes are harvested every year for
human consumption. In some countries, bony fishes may provide up to 50% of all
animal protein consumed (Bond, 1977).
b. Bony fishes are also used to feed livestock, make fertilizer, and produce fish oil.
Metallic paints, leather, glue, and medicines all are made from bony fishes or bony
fish byproducts.
c. Some commercial fishing operations catch large numbers of non-targeted species,
which are discarded. Non-targeted catch is called bycatch.
2. Recreational fishing.
Various species of marine and freshwater bony fishes are targeted for small scale fishing for
food and recreation.
3. Habitat destruction.
a. Damming, channelization, stream diversion, and silting (a result of deforestation or
agriculture) alters aquatic habitats. Sometimes fish populations cannot survive the
habitat changes.
b. The loss of coastal wetlands threatens fish populations, as estuaries are important
nursery grounds for many species of ocean fishes.
4. Pollution.
Chemicals that are used on land can eventually end up in freshwater systems and oceans.
Such chemical contaminants can enter the food chain and become concentrated in the bodies
of fishes.
a. Pesticides may enter waterways through agricultural runoff. Household and garden
pesticides can enter waterways, too-through sewers and storm drains.
b. Small amounts of heavy metals occur naturally in the ocean, but industrial pollution
has increased the amount of heavy metals in many aquatic environments. Heavy
metals may also enter waterways when people empty household chemicals such as
paints into sewers and storm drains.
(1) The effects of heavy metals on fishes is not well known, but we do know
that more than minute amounts of heavy metals are poisonous to humans. The
best known heavy metal poisoning is from mercury. The U.S. Department of
Agriculture (USDA) has set a maximum acceptable level for mercury in fish.
Any fish with more than 0.5 ppm (parts per million) mercury may not be sold
as food.
(2) Heavy metals accumulate in the tissues of organisms that ingest them and
are passed up the food chain. Thus, large carnivorous fishes are most
susceptible to high levels of heavy metals.
c. Acid rain results when the emissions of fossil fuels combine with moisture in the
atmosphere to form droplets of sulfuric or nitric acids. The droplets fall as rain or
snow and can reduce the pH level in lakes and streams to the point where the pH is
inhospitable to native species.
d. Oil spills are harmful for fish populations.
e. The rainbow trout (Salmo gairdneri) is sensitive to degradations in water quality and
has been used to study the effects of various pesticides and waste products on aquatic
life (Bond, 1979).
5. Introduced species. A non-native fish species introduced into a habitat can alter the ecology
of that habitat and may have devastating results on native species. One species native to
Southeast Africa, the tilapia Oreochromis mossambica has been introduced to tropical lakes
and streams all over the world, virtually eliminating many native species.
6. Aquarium collection. Some fishes sold in pet stores are collected using chemicals that kill
many of the fishes exposed to them and destroy other marine life as well. Sea World
encourages aquarium enthusiasts to purchase "hand-caught" or captive-bred fishes.
E. Disease and parasitism.
1. As in any animal population, a variety of diseases can be responsible for bony fish deaths.
These include bacterial, viral, and fungal infections and tumors.
2. Many types of internal and external parasites are common to bony fishes. They include
cestodes, nematodes, trematodes , protozoans, and copepods.
Conservation
A. Endangered and threatened species and populations.
1 . Bony fish species and populations may become endangered or threatened due to
overfishing, pollution, introduction of non-native species, and habitat destruction.
2. As of 1 993, more than 100 species of native bony fishes were considered endangered or
threatened with extinction by the United States Fish and Wildlife Service (USFWS).
Following are a few of the federally listed species:
a. Although the desert pupfish (Cyprinodon macularius) can withstand great
environmental changes, the construction of irrigation and flood control dams has
eliminated the marshy pools where desert pupfish breed. Due to low water levels,
desert pupfish have been forced into mainstream channels where they are preyed upon
by larger fishes.
b. The gila trout (Oncorhynchus gilae) is endangered due to degraded water quality,
overfishing, and hybridization with non-native trouts. Non-native species of trout
introduced for game fishing can breed with the gila trout to produce a hybrid trout. As
gila trout continue to reproduce with other species of trout, their populations will
decrease.
c. The shortnosed sturgeon (Acipenser brevirostrum) has been cut off from many of its
natural spawning grounds along the Atlantic coast by dams. Pollution in major rivers
and estuaries has also been a significant factor in the decline of this species.
d. Perhaps the biggest threats to chinook salmon (Oncorhynchus tshawytscha)
populations are water management projects such as hydroelectric dams, which alter
water flow, hinder migration, and negatively impact traditional spawning grounds.
Poor water quality, overfishing, and inadequate regulations are additional factors
contributing to the chinook salmon's demise.
3. Many other species of bony fishes are listed as endangered by individual U.S. states.
B. Legal protection.
1 . Several federal agencies govern fishing laws and regulations, notably the National Marine
Fisheries Service (NMFS), and the U.S. Fish and Wildlife Service (USFWS). Other federal
agencies that have responsibility for fish management and conservation include the U.S.
Forest Service, The Bureau of Land Management (BLM), and the National Park Service.
2. State agencies such as state Departments of Natural Resources (DNR), state Departments of
Environmental Protection (DEP), and state Departments of Fish and Game may also enact
fishing laws and regulations for the state.
3. Because some fishes (such as tunas and billfishes) migrate through waters under the
jurisdiction of several nations, international cooperation is required for successful
conservation.
C. Aquaculture.
1. An alternative to commercial fishing is aquaculture. Catfish farming is a huge industry in
the U.S. Salmon, trout, sturgeon, and striped bass (Morone saxitilis) are other fishes farmed in
the U.S.
2. In conjunction with the California Department of Fish and Game, the Hubbs- Sea World
Research Institute (HSWRI) raises white seabass (Atractoscion nobilis) fingerlings and
releases them in Southern California coastal waters.
a. HSWRI scientists are developing programs to improve culture technology, evaluate
population characteristics, evaluate habitat requirements, assess stocking methods, and
develop methods to monitor wild populations.
HSWRI scientists continue to develop programs to improve aquaculture technology.
b. To evaluate the hatchlings'success in the wild, researchers insert a coded wire tag
into the cheek muscle of the fish. The tag allows researchers to identify individual
release groups and helps them learn about the population as it develops.
D. Anadromous fish management.
1 - Anadromous fishes hatch in freshwater environments and must travel downriver to the sea
to complete their life cycle. Without assistance, hydroelectric dams would make this
migration impossible. Young fish headed toward the ocean can be barged downriver, sent
over the dam, or guided to a bypass channel.
2. After spending several years at sea, anadromous fishes must travel upriver to spawn. A fish
ladder next to a dam provides a way for these fish to travel upriver.
E. Research.
To conserve fishes and fisheries, scientists continue to study the abundance, reproduction rate
and biology, migration, and catch information on various fish species.
F. Breeding programs.
Breeding programs for several endangered bony fish species are conducted by partici- pating
American Zoo and Aquarium Association (AZA) institutions. Sea World of Ohio participates
in an AZA program dedicated to saving the unique fish fauna of Lake Victoria in the African
Rift Valley.