A Little Bit More
The terms "fish" and "fishes" need to be defined. Although almost everyone uses the term fish exclusively, technically, fish is correctly used to refer to an individual fish or the plural of a single species of fish. The term, fishes, however, refers to the plural of different species of fish.
The typical method fishes obtain oxygen, is to force water to flow over fine capillaries where an exchange can take place: oxygen is absorbed from the water by the haemoglobin while carbon dioxide is released into the water. Most bony fishes have 4 gills on each side of the head. These gills are placed one behind the other to form a series of V's or arches, along the back edge of which are attached the fine filaments with their red, richly supplied capillaries.
Respiration in fishes is more efficient than in land vertebrates, out of necessity, and they accomplish this in 3 important ways.
- An increase in surface area: even though the gill filaments are richly supplied with fine capillaries, this isn't enough for adequate absorption of oxygen. To improve absorption, gill filaments are made up of a large number of tiny, leaf-like lamellae. This increases gill surface area many thousand times, thus greatly improving oxygen absorption.
- Use of the counter-current principal: no matter what point blood and water are in contact, within this system, water has a higher oxygen content than the blood. As blood, now low in oxygen, enters the back of the gills, it first meets water from which most of the oxygen has already been extracted yet is still higher in oxygen content that the blood. Blood that has picked up its quota of oxygen and is leaving the system, contacts the flow of water that has not yet had any oxygen removed in the front of the mouth. Thus, the blood is always in contact with "oxygen rich" (by comparison) water and at no point in the system, is the blood likely to loose oxygen to the water.
- Maintenance of a constant water flow: the mouth cavity and gill cavity work in concert to form a double-chambered pump. Water is sucked into the mouth, which then closes, and is compressed to force the water into the gill cavity then out through the gill slits. The two chambers work slightly out of phase with each other resulting in a continuous flow of water through the system.
A fish's breathing frequency is closely linked to both habitat and its current activity level. A balance must be reached since the faster the breathing, the more oxygen is extracted, but also the more energy is required. As you might expect, when resting, the rate tends to be slower. In certain fast-swimming fishes (mackerel, for example) the pumping action of the mouth and gills is not used at all and water is simply allowed to flow freely through an open mouth and gill cavity as they swim. In an opposite situation, where there is stagnant (still) water with little available oxygen, some fish (goldfish for one) can even gulp air at the surface to augment their oxygen supply.
Activities
Science - Breathing Fish
Objectives: Observe how fish breathe
Materials: Access to fish in aquariums or clear body of water
Actually, being able to see a fish breathe is not as difficult as you may think. For those of you with a goldfish or tropical fish at home, it's easy. If you live near a stream, pond, or lake, it's fun to quietly creep up on the bank and see fish in a natural environment - as long as it's clear enough. If you can't do this, go to your local pet store and you'll find a large number of fish to watch.
The larger the fish, the easier it will be to see so at first choose one of the larger individuals. Larger animals tend to breathe more slowly than smaller ones and you can see this for yourself by comparing a large fish with a small fish. For 15 seconds count how many times each fish opens its mouth and then multiply by 4 to find out how many times it breathes per minute. Keep in mind that a relaxed, quiet fish breathes more slowly than one that is excited and active (just like you). Be sure to count breaths only from fish with similar activity levels. Fish breathe more often in warm water than cold water - can you come up with an experiment to test this information?
Key Concepts
Behavior and Regulation, Structures and Functions
Questions
Do you have a question for a naturalist? Go ahead and ask!
It's easy -- just fill out this form, submit your question and you'll receive an answer shortly.
Posted by andrew piekutowski on May 25, 2006 at 12:11 PM
Q: What level of oxygen does a tropical fish need?
A: When you mention "tropical fish" you're covering a lot of ground. There are many different kinds of tropical fishes and they have different levels of oxygen requirements. In general, the more active fishes are those requiring a higher level of oxygen in the water. So, a fish like a catfish that lies on the bottom most of the time would require much less. If you have a filter and/or bubbler in your tank, your fish probably have adequate oxygen as long as your tank isn't overcrowded. There is a general "rule of thumb" that states that there should be no more than 2.5 centimeters (one inch) of fish (length) for every 4 liters (1 gallon) of water. Hope this helps you out.
Posted by Axel Gomez on May 22, 2006 at 03:34 PM
Q: Can marine iguanas breathe underwater?
A: Marine Iguanas can not breathe underwater - they have lungs just like you. In fact, no reptiles can. Sea Snakes are especially well adapted for life in water - much more so than Marine Iguanas - and they too are unable to breathe underwater and must surface periodically to breathe air.
Posted by rikki whalen on March 24, 2006 at 07:42 AM
Q: how do snakes breathe ?
A: Snakes don't have a diaphram as we do so must use muscles along their sides to expand and contract their lungs. Most snakes have only one main, functional lung but it functions much as ours does to obtain oxygen. When a snake is feeding on a large prey item it can also push its trachea (windpipe) off to the side so it can still breathe with a mouth full of food.
Thanks for asking.
Posted by sophie l on March 14, 2006 at 10:39 PM
Q: With snakes where does there gas exchange take place? and How does oxygen and carbon dioxide get carried around the body?
A: Snakes have a lung (they only have one that's functional) just as we do to make the oxygen exchange from air to blood. They also have blood that circulates within their body to provide oxygen to all of the cells. Thanks for asking.
Posted by Carmen McGhan on March 12, 2006 at 08:56 PM
Q: Does the temperature of the water affect a fish's breathing? this is a hypothesize question.
A: Yes, it does. Water temperature has two effects on fish. Warmer water holds less dissolved oxygen than colder water so a fish needs to "work" a bit harder to get the oxygen it needs. Furthermore, warmer water also means a fish's metabolism is higher and therefore needs more oxygen too. So you can see that, all things being equal, a goldfish living in cold water is going to have a different breathing rate than one living in warm water. Thanks for your question.
Posted by sami on June 02, 2005 at 07:32 AM
Q: why do fish need a larger surface area to extract oxygen from the water then an animal of similar size would need on land?
A: Because there is much less oxygen available to animals living in the water than there is on land. In the air, at sea level, there is about 21% oxygen available to a lizard, for instance, but much less oxygen is present in water (oxygen levels can vary a great deal in water). Therefore, organisms living in water must be much better at "capturing" that oxygen to ensure they have enough for life. Ectotherms (cold-blooded animals) need less oxygen than endotherms (warm-blooded animals) but if you compare a lizard with a fish, the fish must be better at obtaining its oxygen needs than the lizard simply because it is living in an environment that has less oxygen available. I hope this helps. Thanks for you question.
Posted by Anonymous on April 10, 2005 at 02:09 AM
Q: How do fish get oxygen from plants?
A: They get their oxygen in much the same way you do - by removing it from the medium (air or water) in which they live. Water plants produce oxygen during photosynthesis(they don't give off oxygen at night or when not photosynthesizing). Some of this oxygen gets dissolved in the water and is then available for organisms to remove for their own needs. Land plants do the same and we, of course, are able to breathe that oxygen from the air.
Much of the oxygen that is dissolved and available for aquatic and marine organisms has gotten there as water and air have mixed, not just from water plants. In other words, as streams tumble over rocks and waterfalls, and as the wind whips up waves on a lake or ocean, oxygen is being absorbed by the water. So, both water plants AND land plants are providing oxygen for organisms living in water. Thanks for your question.
Posted by Anonymous on March 13, 2005 at 03:42 PM
Q: why are a fishes' oral movements greater than their operculum movements?
A: Wow, you've been observing and thinking! It took me a moment to think this over but I believe I have the correct answer. Water entering the oral cavity must come through a single opening - the mouth. Water leaving the oral cavity, leaves through 2 openings - the gill slits. I think too that the mouth movements also help to push water through the oral cavity so must be stronger in action than the opercles. Hope this answers you question.
Posted by yoonjo ahn on February 28, 2005 at 04:49 PM
Q: As the water temperature decreases, the fish?s operculum and oral movements will also decrease.
Is this true? i did a science lab and am doing a lab report. i need info to back it up. Do a fish's oral and operculum movements differ and why?
A: Yes, it is true. Fish are cold-blooded animals (ectotherms) and as they cool, their metabolism slows down and they need less and less oxygen. A fish's mouth and gill flaps (opurcula) move in rhythm to their need for oxygen; the more oxygen they need, the faster they move, the less oxygen they need, the slower they move. Be sure you read the unit poster so you understand what is going on. Hope this helps.
Posted by Trena Phenix on February 03, 2005 at 11:18 AM
Q: We live on Great Bear Lake in the Northwest Territories, Canada. Our lake holds trout, jackfish, greyling, whitefish and we want to know how the fish get oxygen when the lake is frozen. Our lake freezes in October and doesn't thaw until the summer (June). THe ice is so strong that it is used for a road in the winter. How do fish get oxygen when the surface is ice?
A: Good question! Although a lake may be sealed over with ice, the water does have a certain amount of oxygen dissolved in it that is available to aquatic life. I'm not familar with Great Bear Lake but if there are lots of streams feeding this lake, these will bring in oxygen too although maybe not enough to sustain life throughout the entire lake in winter. As you would expect however, over time as organisms use up oxygen in an "ice-sealed" lake, the oxygen level will slowly drop over time if it can't be replenished. If the oxygen level does drop too low, then there will be a die-off of organisms. But, since some organisms can tolerate lower levels of oxygen than others, a die-off hits those that require higher levels for survival first - trout are especially susceptible to low oxygen levels and probably are one of the first to be adversely affected.
There are many variables at work in your lake that affect whether there will be enough oxygen for life under the ice throughout the winter. One important variable is the ratio of water volume to animal life present - the greater the water volume and the fewer organisms present, the more oxygen is available. Another variable is whether there is a lot of plant life in the lake - dead plants in winter are broken down by bacteria which use oxygen so if there are lots of decomposing plants, there will be less and less oxygen available for animals. Keep in mind too that in the cold water, all of the organisms have a slower metabolism and therefore need less oxygen to survive so that works in their favor.
With all that said, probably the worst setting for adequate oxygen levels throughout the winter would be a shallow lake with lots of plants and animals that has been completely sealed over with ice. Conversely, the best setting for high oxygen levels would be a large, deep lake with little plant and animal life that is sealed over. Hope this helps.
Posted by Jean Newton on April 15, 2004 at 03:01 PM
Q: What do the bubbles mean that form on top of a filterless fish tank?
Some say the fish need more oxegyn. Some say it is an indication that the fish are breathing.
What do you say?
A: I've never been entirely clear myself, why one has bubbles one time and not another in an aquarium. I do think it has to do with material in or on the water that is cohesive (sticks together) and forms these bubbles. I also think there needs to be some water movement or agitation for these bubbles to form; your pump's action is probably making it possible for the bubbles to form but is not the ultimate cause. Although many think immediately of pollution, this is definitely not ALWAYS the case. I'd take my cue from your fish; if they're acting normally, have good color and not breathing with greater urgency (their gill covers moving more quickly than usual), I'd not worry. One thing to be careful of is not overfeeding. This can leave uneaten food in their tank and may cause some problems - whether in the form of bubbles or just yucky water, I really can't say. Good luck with your fish.
Posted by Jonathon on March 24, 2004 at 09:41 PM
Q: How do reptiles breathe?
A: They breathe like you do - Their chest expands, reduces the pressure in their lungs and air rushes in. To expell air, they contract (squeeze) their chest and force the air out.
Posted by Maya on January 18, 2004 at 04:19 PM
Q: How do bears get enough oxygen to breathe during hibernation if their dens are covered up with snow & ice?
A: Bears don't hibernate - see "The Real Ones" coming up for March 21. They do sleep quite a bit in winter and find out-of-the-way places to do so. Snow and ice does cover their dens however it would be very unlikely for it to seal out air. Remember too that the bears' deep sleep would reduce their oxygen requirement so any reduction in access to air is probably offset by their slowed metabolism. If a bear had selected a site that became sealed to outside air, I suppose it's possible that it would suffocate before it realized its situation.
Posted by anonamous on November 23, 2003 at 09:00 PM
Q: how do snakes breathe? do they breathe form there mouths or there tails. i have a scince essay due and i need to know cause i am doing it about living things.
thanks
Anonomous
A: Snakes have a windpipe (trachea) just as we do in the back of their throat and this is how they get air for breathing. A snake can move its trachea out of the way, unlike humans, when it is eating a large animal so it can still breathe as it swallows.
Posted by giannis on November 19, 2003 at 06:07 PM
Q: i have two goldfishes and especially at night time they go to the surface of the tank, does this mean that they need more oxygen? is it normal? thank you
A: Goldfish have the ability to supplement their oxygen needs by gulping air at the surface. This strategy works well for some fish living in waters that are not always adequately oxygenated - this will get them past those times when other fish might not survive.
Yes, I think your fish are in need of more oxygen. Your easiest remedy would probably be to provide more water - larger tank. An inch of fish for a gallon of water is a good rule of thumb, and keep in mind too that the warmer the water, the greater their oxygen needs. Hope this helps.
Posted by Sandra Herring on March 30, 2003 at 07:09 PM
Q: I went to a fish market one day and noticed that a white bubble was inside a black bass's mouth and I also noticed that a Whiting had a pink bubble in its mouth! What are those bubbles and do they come in all kinds of colors?
A: Wow, you're very observant! I think I know what you're seeing. I'm afraid that fish don't have multicolored bubbles though.
Fish have quite a bit of mucus on their bodies and in their mouth too, especially if traumatized (as when caught or hooked). The white bubble you saw was probably a mixture of air and mucus (much like the bubles one might see in a babies mouth) that resulted from the fish's struggles. The pink bubble, on the other hand, is probably a combination of air, mucus, and blood, also as a result of the fish's struggles
Posted by Lori Williams on November 25, 2002 at 03:16 PM
Q: Why do fish breathe more in warmer water
A: Their metabolism (chemical reactions are happening more quickly)is higher when they are warmer and therefore they need more oxygen to help fuel this activity. Warm-blooded animals (endotherms) need more oxygen than cold-blooded animals (ectotherms). This is one reason that animals like snakes, fish, and turtles can often go for rather long periods without food and not suffer. Mammals and birds need much food to help fuel their higher activity levels and can only stop eating if they hibernate.
Posted by Philip Lewis on November 24, 2002 at 09:03 AM
Q: Compare how any fish breathes to how a human breathes
A: Of course, both humans and fish need oxygen but humans get their oxygen from air while fish get theirs from water. Fish take in mouthfuls of water and this passes over the gills and out of the gill slits (openings on each side of the head). As the water passes over the gills, the oxygen enters the fishís blood stream. Humans, on the other hand, bring air into their lungs by expanding their chest. As their chest expands (gets larger), air rushes in through the nose (or mouth) and into the lungs and this is where the oxygen enters our blood.
You can probably say that fish respiration is more obvious ( you can see what most fish are doing) than respiration in land animals, including humans.