fish digestive system

Structure of the Digestive System
Irrespective of their main dietary requirements, the digestive systems of fish are very similar. All have a mouth, oesophagus (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) whilst herbivorous or plant-orientated omnivores have no stomach but rely on a much extended midgut area. These two situations are shown below.
Digestive system of a Carnivorous Fish



Digestive system of a Omnivorous Fish

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.
Before being digested, the fish food, whether live or in the form of a pellet, has to be caught and positioned before being 'swallowed' - this is the function of the mouth. In carnivorous or predatory fish teeth may be present on the jaws, tongue and inner mouth (buccal cavity) - these teeth do not bite or crush food but simply hold it and prevent escape. Herbivorous fish or those which feed on hard-shelled prey may have pharyngeal teeth to aid in crushing the food before it enters the stomach. The oesophagus is a tube which connects the mouth to the stomach and/or gut - no food absorption occurs here.
For those fish species with a stomach, two areas can be identified - a cardiac area anteriorly (i.e. food enters this part of the stomach from the oesophagus) and the pyloric section posteriorly (where food exits from the stomach into intestinal tract). The stomach wall secretes hydrochloric acid and digestive enzymes which serve to soften and initiate breakdown of food into smaller, absorbable pieces. In stomachless fish, the wall of the anterior midgut secretes digestive enzymes but not hydrochloric acid.
From the stomach the intestine (comprising mid and hindgut) runs to the vent/anus. In carnivorous fish the intestine is relatively short whilst that of herbivorous fish, which tend to lack a stomach, is long and much folded to increase the contact and absorption time. At the anterior end of the midgut a number of blind ending tubes may be present - these are the pyloric caecae. They appear not to be associated with any particular type of diet and the number, if they are present, varies from species to species. Several functions have been attributed to them including increasing the surface area of the intestine for food absorption, specific site of carbohydrates and fat absorption and adding to the digestive functions of the stomach. Caecae are present in salmonids but absent from cyprinid species.
An important source of digestive enzymes is the pancreas. This organ is adjacent to the stomach and can be a discrete or diffuse organ depending on species. In salmonids the pancreas is a diffuse collection of cells interwoven amongst the pyloric caecae. Enzymes are produced by the pancreas only in the presence of food and are involved in the breakdown of all nutrients.
Both the liver and the gall bladder play an important role in digestion. The liver both assimilates the products of digestion into usable forms and aids the digestive process through the production of bile which is stored in the gall bladder.
Bile serves a number of functions in that it (a) helps with emulsification and absorption of lipids/fats, (b) neutralises hydrochloric acid from stomach (and so prevents possible ulceration of the intestine) and (c) ensures that absorbed toxins are returned to the intestine for excretion.The size and fullness of the gall bladder is indicative of feeding status in fish. A large, distended bladder indicates that the fish has not eaten for some time whilst an empty flaccid bladder indicates that the fish has recently eaten a meal. Bile is excreted from the bladder to the intestine via the bile duct.

Fish Information

• A life cycle is the continuous sequence of changes undergone by an organism from one
  primary form to the development of the same form again.
  Metamorphosis means transformation; it involves the loss of the features which mark an
  individual as a larva, and the attainment of those which characterize it as an adult.
  Complete metamorphosis consists of four stages: 1) egg, 2) larva, 3) pupa, and 4) adult. It
  commonly occurs in insects where the earliest stage of development looks significantly
  different from the adult.
  Incomplete metamorphosis occurs where there are fewer than four stages, which is the case
  for many fish. Shortly after they hatch, many fish essentially have all the features of an adult.
  A typical fish life cycle starts with an egg. The egg hatches into what is called a yolk sac fry -
  a larval stage where the fish has an attached yolk that provides it with nourishment for its first
  week or two. The true larval stage begins when the fish has absorbed the yolk and starts
  feeding for itself. When the fish gets bigger and looks very much like an adult, it is considered
  a juvenile. Once the fish matures and can reproduce and lay eggs, it becomes an adult.
• Catfish are different from many other fish in that the male catfish cares for the eggs and yolk
  sac larvae. Catfish eggs are 3.5-4.0 mm in diameter. They are laid in a gelatinous mass in a
  nest constructed by the male catfish in holes or burrows, under rocks, logs, or overhanging
  riverbanks. The eggs are yellow when laid but become browner as hatching nears. They hatch
  in 5-10 days. The male catfish fans water over the eggs to aerate and clean them; once they
  hatch, he protects the young for several days until they swim off to feed. The yolk sac larvae
  have large yolks and are about 6-10 mm in length. Their bodies are transparent with some
  pigmentation on the tops of their heads. Their barbels or whiskers are very long compared to
  their head. Their tails change from a club-shape to more obvious double lobes which are quite
  rounded. The yolk sac larvae stay on the bottom for 2-5 days, and then swim to the surface to
  feed. Catfish do not exhibit a post-yolk sac larval stage.
  Juvenile catfish are 15-42 mm in length. They look very much like an adult with their sharplypointed
  forked tail. Younger juveniles are nearly white with small brown spots that are more
  obvious over their fins. The darker colour spreads as they grow older.
  Catfish mature and become adults when they are 5-8 years old. They are dusty-grey to dark
  grey-blue in colour, often with scattered spots. Adults can weigh over 14 kilograms!
  The prehistoric-looking lake sturgeon is one of the largest freshwater fish in North America,
  reaching lengths of 2.5 meters and weighing more than 140 kilograms! It starts its life as a
  sticky, tiny (about 3 mm), dark egg that attaches to rocks and logs or wherever it lands when
  laid by the adult female. The sturgeon egg is unusual in that it has holes in its surface - up to
  13 of them - called micropyles, which allow sperm to rapidly penetrate the egg as it tumbles
  through the water. The egg hatches in 5-8 days. Newly hatched, the little 8 mm yolk sac fry has
  a huge yolk. Its eyes and body lack pigment but the yolk sac is covered with fine black spots.
  The larval stage begins when the tiny sturgeon has absorbed the yolk sac, about 9-18 days
  after hatching. At this time, the sturgeon is about 22 mm long, its four barbels appear, its nasal
  opening is evident, its snout is longer and more slender, and its back is completely covered
  with small evenly-spaced black dots. A dark band extends from its snout through its eye and
  blends into the pigmentation near the fin on its back. At this stage, a young sturgeon looks like
  a miniature of an adult.
  The little sturgeon is considered a juvenile when it is between 196 mm and 762 mm in length.
  The juvenile stage lasts from about the age of one year to the onset of maturity at about 15
  years old. At age 1 (about 196 mm), the sturgeon's tube-like sucking mouth and barbels are
  fully developed, and it has five rows of bony plates (called scutes) on its body. The scutes have
  well-developed keels terminating in a sharp, pointed hook or spur. In larger (greater than 1
  metre), older sturgeon, this hook will wear off and skin will grow over it.
  As an adult, the sturgeon has lost its large blotches and is olive-brown to grey on its back and
  sides, and white on its belly. Its scutes are worn and thin. It is more round in cross-section than
  the more angled shape of the juvenile. Its snout has also shortened. Because adult sturgeon
  grow so large (over 2 meters), they have no predators except humans. They are much older
  than other fish when they mature (15-20 years) and they do not lay eggs every year.
  

Hatchery Q&A

Hatchery Questions

Q. What are the Key Roles of Hatcheries?

A. Hatcheries Support:

• Salmon Alevins (Sac Fry)

  Supplementation, which routs a portion of imperiled wild population through a hatchery for part of its life cycle to gain a temporary survival boost
  
  
• Restoration, which outplants suitable non-local hatchery-produced or naturally-produced native fish to establish a population in habitat currently vacant for that native species
  
  
• Captive broodstock collection, which takes some or all of an imperiled wild population into a protective hatchery environment for its entire life cycle to maximize survival and the number of progeny produced
  
  
• Captive Rearing, which takes a portion of an imperiled wild population into a protective hatchery environment for only that part of its life cycle that cannot be sustained in the wild
  
  
• Egg Banking, which temporarily removes a naturally produced native fish population from a habitat that cannot sustain it and relocates the population to another natural or artificial area that can support the population
  
  
• Cryopreservation, which freezes sperm from naturally produced native fish for later use in conservation hatchery programs
  
  
• Research, which investigates and resolves uncertainties relating to the responsible use of hatcheries as a management tool for fish conservation and use
  

Q. What are the primary fish species reared at hatcheries?

A. Chinook: Also known as king salmon, these fish migrate to sea after one year in the hatchery. They return to the hatchery after three or four years in the ocean. Their average weight at spawning is 10-45 pounds. Some species return in the fall, others in the spring. All chinook spawn in September, October or November.
Coho: Also known as silver salmon, these fish are released from the hatchery after 18 months. Adult coho return at age three after more than a year at sea. An average coho weighs about eight pounds when it returns to spawn in the fall.
Steelhead: Steelhead are rainbow trout that go to sea. They are released from hatcheries at about one year of age and spend up to four years at sea before returning to spawn in freshwater. Different strains of steelhead return at different times of the year, but most spawn in late winter. An average steelhead weighs about six pounds.
Trout: Rainbow, brook and cutthroat trout are the principle hatchery species. With the exception of cutthroat trout, these fish spend their lives in freshwater. ODFW raises and releases more than 7 million trout annually. Eggs for production are either taken from brood fish held in the hatchery or from fish trapped and spawned in the wild.

Q. What happens to adult salmon and steelhead after they return to the hatchery?

A. In the wild, salmon die naturally after spawning. At hatcheries, workers euthanize the fish before removing eggs from females and extracting milt, or sperm, from males. Eggs and sperm are mixed, then placed in special incubators. Development from a fertilized egg to a small swimming fish, called fry, takes about two months.
Steelhead are sometimes euthanized prior to spawning, but not always. Some fish may be released back into the river.
Trout hatcheries maintain brood stocks of adult fish that may provide eggs and sperm for several years. ODFW often releases the oldest trout, some weighing five pounds or more, into local ponds for people to catch.

Q. When is the best time to visit a hatchery?

A. Fall and early winter are the busiest and most interesting times at salmon and steelhead hatcheries. That's when the adults are in the holding ponds and spawning is under way. Spring and early summer are the peak activity times at trout hatcheries. Spawning and most fish stocking operations occur during those months.

Wildlife Area Questions

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Q. Why does Oregon set aside lands for Wildlife?

A. In general Oregon has a lot of land that serves the needs of wildlife very well. Even so, some special requirements are in short supply. Sometimes the only way to preserve such places is to publicly manage them.
Wetlands, for example, are necessary for waterfowl such as ducks and geese. These are the places where migrating birds rest and feed during their spring and fall travels. Many birds also nest and raise their young in wetlands.
Deer and elk need places to go during winter to find shelter and food. These winter ranges are critical to maintaining healthy herds and preventing animals from moving onto and damaging agricultural lands.

Q. Are wildlife areas set aside for both hunted and non-hunted wildlife?

A. Yes. The same wetlands, winter ranges and other areas that serve game species also meet the needs of other wildlife. Wetlands, for example, provide major resting, wintering and breeding areas for species as diverse as shore birds and bald eagles. Woodpeckers and hawks thrive on many of the upland wildlife areas. Hunter dollars pay for purchase and maintenance of these areas, but the benefits go to all species. Many of these areas also are popular with people who do not hunt, but would rather hike, fish and view wildlife.

Q. Does buying property for a public wildlife area take money from the county property tax tolls and local service districts?

A. No. The Oregon Department of Fish and Wildlife pays more than $180,000 each year in what are called "in lieu of" taxes or assessments for wildlife area lands. This equals the amount that would have been paid to counties and service districts if the lands were privately owned. In addition, wildlife areas generate economic benefits for counties and local communities. Most sites attract visitors who spend money in local communities, whether they are hunters in the fall or hikers and wildlife viewers year-round.

learn about the dog

Dogs have live births, usually in litters of around six puppies.  They are mammals, so in addition to giving live birth, they have fur and produce milk for the babies.  How long a dog lives varies by breed, but most dogs live 12 to 14 years.  A puppy is considered an adult dog at the age of about one year.

For some math fun:  Some people say that one human year is equal to 7 dog years. They say this because dogs become adults when they are between one and two years old.

If you are eight years old, how old is that in dog years?  Find out what your age equals in dog years!Butterflies are also insects, and hatch from eggs into larvae.  The larvae, also known as caterpillars, eat leaves while they grow.  After several days they make a cocoon and go through a pupal stage to become a butterfly.  The lifespan of a butterfly is 20-40 days.

For some craft fun:  Make your own butterfly life cycle. Draw, color and cut out a picture of each part of the butterfly life cycle. Punch a hole in the top of each picture. Thread yarn or string through the hole and tie the other end to a coat hanger. You have a mobile!

Life Cycle

• The typical female dog becomes sexually mature by the age of one. Some females mature by 6 months, others by the age of 18 months. The typical male dog becomes sexually mature by the age of one. An adult female dog is called a bitch; an adult male dog, a dog, or, if used for breeding, a stud.
• A sexually mature female dog goes into heat (enters a period of sexual receptivity) twice a year for a period of about 10 days. During this time, the female emits an odor that attracts males.
• After a gestation period of 63 days, the female whelps (gives birth to a litter of puppies). A litter may consist of up to 15 puppies, depending on the breed. Some breeds, such as the Pomeranian and Chihuahua, typically give birth to small litters, generally no more than three puppies; other breeds, such as the Airedale terrier and Great Dane, generally give birth to litters of 5 to 12 puppies.
• Puppies are born with their eyes closed and do not open them until they are about 10 to 14 days old. Puppies grow rapidly and are ready to be weaned about six weeks after birth. At this time, they have all their milk teeth. The full set of 42 permanent teeth (22 in the lower jaw and 20 in the upper jaw) begins to erupt when a puppy is about five months old. Dogs usually reach full growth and maturity by the age of two.
• The average life span of a dog is 12 years, although some dogs live 20 years or more. As a dog ages, the hairs around its muzzle and face become white or gray. Many old dogs suffer from arthritis, cataracts, hearing loss, and kidney disorders.

About the horse

Horse Life Cycle Facts
Newborn Foal	Yearling	Adult Horse
Ø  A newborn horse is called a foal.  Ø  The mother feeds the foal her warm milk for a year.  Foals also eat grass and hay after a few weeks.  Ø  Foals can walk, but they have wobbly legs at first.	Ø  When a horse is one year old, it is called a yearling.  A female yearling is called a filly and a male yearling is called a colt. Ø  A yearling starts to learn how to carry a rider.  Ø  A yearling is usually the same size as its parents.	Ø  A female horse is called a mare.  A male horse is called a stallion. Ø  A mare will mate with a stallion in the springtime.  Ø  A female horse carries a baby inside her for almost a year.

• During the first 12 months the foal/filly  has long legs compared to its body.  After two months the foal/filly sheds its milk hairs.  Two months later it would stop drinking milk from its dam (mother).  After it has passed drinking milk from it's dam, it is considered a horse.
• A 12 month becomes a Yearling on January 1.  At 12 months the baby horse is still uncoordinated in movements,  and quite leggy, but their frame is beginning to fill out.  This is an ongoing process until maturity, when it's hind quarters, or croup, are in line with it's withers, the part right below the neck.  The last parts of growth are the epiphyses or the growth plates on the very long bones of the legs.  Until these are closed, the horse isn't able to keep working because they are too weak.  This happens particularly when they are under weight, without the risk of the legs being damaged.  The epiphysis is located at the end of the cannon bone, over the fetlock joint, an\ usually is closed in the middle of nine and twelve months.  
•     After this it goes on to Middle years.  These are when it is 5-10 years old.  By then the horse is fully formed.  After this stage it goes on to Late years when the joints might become puffy as the circulation might become lass effective.  Then the effects of work will start to show.  This is the horse life cycle.                         
• The  foal/filly is born with no teeth.  As it gets older, the horse grows teeth.  By the time the foal/filly is six to nine months, the young horse has all of it's milk teeth.  At five to six years of age, the horse replaces it's milk teeth with it's  permanent teeth.  You can tell how old a horse is by it's teeth.  When it becomes older it becomes even easier to tell because of the "Galvayne Groove" on the corner of the incisor of the upper jaw.

fish life cycle

Fish Life Cycles

• A frog is an amphibian. It starts its life in the water and then moves onto land when it becomes an adult. They also have moist skin. Amphibians lay eggs. The eggs stay in the water and hatch there. The young amphibians live in the water.
• There are four parts of a frog's life cycle:  Eggs, tadpoles, young frogs, adult frogs.
• Young frogs are called tadpoles. They look very different from adult frogs. They look more like fish. They breathe with gills. The gills help them get oxygen from the water.
• As the tadpoles grow they change. They begin to grow lungs that they will need when they are adults. When their lungs are big enough to help them breathe, their gills start to disappear.
• Tiny bumps appear on their bodies. These bumps grow into short front legs and longer, stronger hind legs. Once their legs are grown their tails begin to disappear. Then they look like adult frogs and are ready to live on land part of the time, but they usually stay close to water even when they are adults.
• Turtles are reptiles. Most of them live on land and use lungs to breathe air.
• Many reptiles are hatched from eggs that have been laid on the sand. Turtle eggs have a very tough shell. Once they hatch, they are ready to live on their own. They don't need mothers to take care of them.
• Math Fun:  A loggerhead turtle lays 108 eggs and they all hatch. Another loggerhead turtle lays 94 eggs and they all hatch. Another loggerhead turtle lays 103 eggs and they all hatch. If the eggs hatch at the same time, how many baby turtles will be crawling to the sea after they hatch
•  Chickens are birds, so they are hatched from eggs.  They have a special  horn on their beak to help them break the egg, and when they are born they only have fine down and no feathers.  They’re called chicks, and are considered fully adult at 32 weeks of age.  Chickens can live from 5-10 years.
  Craft fun:  Draw an outline of a chicken. Get some colorful feathers (you can buy these at Wal-Mart or craft stores). Glue the feathers onto the chicken. Try to arrange them so that they look real. Glue two pipe cleaners in place as the chicken feet. Put two googly eyes on the chicken's head, and a small piece of construction paper for its beak. You made a chicken!

Frog Life Cycle

Life Cycle of a Frog

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True Love? When Frogs mate, the male frog tends to clasp the female underneath in an embrace calledamplexus. He literally climbs on her back, reaches his arms around her "waist", either just in front of the hind legs, just behind the front legs, or even around the head. Amplexus can last several days! Usually, it occurs in the water, though some species, like the bufos on the right mate on land or even in trees!(photo courtesy of Emile Vandecasteele)
While in some cases, complicated courting behavior occurs before mating, many species of frogs are known for attempting to mate with anything that moves which isn't small enough to eat!

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Spawn (egg-mass) While in the amplexus position, the male frog fertilizes the eggs as they get are laid. Frogs tend to lay eggs single eggs in masses, whereas toads usually lay eggs in long chains.
Some frogs leave after this point, but others stick around to watch over the little ones. Some have very unusual ways of caring for their young. You'll learn about some of those later in this tour!. 

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Egg Frogs and Toads tend to lay many many eggs because there are many hazards between fertalization and full grown frogness! Those eggs that die tend to turn white or opaque. The lucky ones that actually manage to hatch still start out on a journey of many perils.
Life starts right as the central yolk splits in two. It then divides into four, then eight, etc.- until it looks a bit like a rasberry inside a jello cup. Soon, the embryo starts to look more and more like a tadpole, getting longer and moving about in it's egg.
Usually, about 6-21 days (average!) after being fertilized, the egg will hatch. Most eggs are found in calm or static waters, to prevent getting too rumbled about in infancy!
Some frogs, like the Coast foam-nest treefrog, actually mate in treebranches overlooking static bonds and streams. Their egg masses form large cocoon-like foamy masses. The foam sometimes cakes dry in the sun, protecting the inside moisture. When the rain comes along, after developement of 7 to 9 days, the foam drips down, dropping tiny tadpoles into the river or pond below.

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Tadpole Shortly after hatching, the tadpole still feeds on the remaining yolk, which is actually in its gut! The tadpole at this point consists of poorly developed gills, a mouth, and a tail. It's really fragile at this point. They usually will stick themselves to floating weeds or grasses in the water using little sticky organs between its' mouth and belly area. Then, 7 to 10 days after the tadpole has hatched, it will begin to swim around and feed on algae.
After about 4 weeks, the gills start getting grown over by skin, until they eventually disappear. The tadpoles get teeny tiny teeth which help them grate food turning it into soupy oxygenated particles. They have long coiled guts that help them digest as much nutrients from their meadger diets as possible.
By the fourth week, tadpoles can actually be fairly social creatures. Some even interact and school like fish! 

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Tadpole with legs After about 6 to 9 weeks, little tiny legs start to sprout. The head becomes more distinct and the body elongates. By now the diet may grow to include larger items like dead insects and even plants.
The arms will begin to bulge where they will eventually pop out, elbow first.
After about 9 weeks, the tadpole looks more like a teeny frog with a really long tail. It is now well on it's way to being almost fullgrown! 

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Young Frog, or Froglet
By 12 weeks, the tadpole has only a teeny tail stub and looks like a miniature version of the adult frog. Soon, it will leave the water, only to return again to laymore eggs and start the process all over again! 

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Frog

By between 12 to 16 weeks, depending on water and food supply, the frog has completed the full growth cycle. Some frogs that live in higher altitudes or in colder places might take a whole winter to go through the tadpole stage...others may have unique development stages that vary from your "traditional" tadpole-in-the-water type life cycle: some of these are described later in this tour.
Now these frogs will start the whole process again...finding mates and creating new froggies.