Why dont freshwater fish drink water?
453845
Because of osmotic pressure.\n\nThe water in the fish's body is full of impurities.  You know, fish parts.  Osmosis causes water to flow automatically to less "pure" concentrations.  So, a freshwater fish has no need to drink, the water is simply pumping into it's cells.  In fact, it has to work extra hard to get waste water out of it's system so it doesn't swell up and explode!\n\nSaltwater fish have the opposite problem.  The salt in the water turns the osmotic pressure around and the oceans are constantly pumping water out of saltwater fish.  They have to drink to make up for it.
166054
There’s a fairly complicated evolutionary history to this trait. Trout started out initially as freshwater fish. As time went by their ancestors moved initially into brackish rivers, then into estuaries and finally into the oceans. But because they evolved in freshwater their eggs could still only survive in freshwater. So every year the trout ancestors had to move from the ocean back into the freshwater.\n\nBut as trout moved through the oceans they gradually discovered new rivers and streams in new countries, or streams that had just recently formed. Trout bred in those new streams, and some of them never moved back to the oceans. As a result today  there are lots of different types of trout. While most move back to the oceans after they hatch some live out their entire lives in freshwater. Others, like the steelhead, can do either, with some individuals returning to the oceans and some staying in the freshwater where they were born.\n\nBut because all trout ancestors evolved to swim from the ocean back up the freshwater streams most trout do the same today. Even those trout that never leave the freshwater feel that same urge to move higher upstream. But it should be noted that some trout species don’t swim upstream. Instead they swim towards clean water, which in many places can be downstream. But they still retain that same ancestral urge to migrate when it comes time to spawn.\n\nOddly enough many species of fish do exactly the opposite. These fish evolved in saltwater and although they spend most of  their lives in freshwater rivers and lakes they return to the ocean to spawn. The best known examples are the eels. The world contains lots of eels species that live in freshwater, but all return to the deep ocean where they first evolved in order to mate and lay eggs. Then the babies swim thousands of miles up out of the abyss and back up the same rivers their parents left.\n\nBiologically speaking trout swim upstream in repsonse to sex hormones that cause them to first seek highly oxygenated water and then to fight the current.\n____________________________________\n\nAddenda\n\nDogsmyjob said "Trout are fresh water fish only."\n\nI have no idea where you get yuour information, but you are completely and utterly incorrect. Most trout species remain anadromous, ie they return to the sea as adults. Why do you think there are  several species called sea trout?\nDon't believe me? Folow the links below.\n\nBut hey, at least you learned something today. \n\n"Anadromous bull trout rear in natal streams and migrate to marine environments to mature."\n\n"Rainbow trout are primarily a freshwater fish, although sea-run populations, often known as steelhead, exist in some areas. It is unclear whether this migration to sea water is genetic or simply opportunistic, but it appears that any population of rainbow trout is capable of migrating to or surviving in the sea if the need arises "\n\n"The shoals drop downstream during the night. A 'spate' will mitigate the change from fresh to salt water and particularly at these times the fish migrate to sea. Those fish not migrating return upstream for one more summer's growth."
35913
Well, generaly, a large fish is bound to only swim in the ocean because there is enough space for it. Also it depends if the fish lives in salt water versus fresh water.
695857
osmosis\nbecause there is a higher water potential inside the seahorse. the sea contains more salt than the seahorse (suprisingly! Lmao) so there is more water in the seahorse. the water molecules travel down the concentration gradient and so the seahorse loses water. though as it is in the sea i doubt this really bothers it
584296
because without it they wouldn't be alive. It is necessary for plants and animals to live. There wouldn't be rain, and oceans, and lakes without it. There are thousands of reasons for why people worship water, because it's WATER!
628752
Unlike marine mammals such as whales and dolphins with lungs that store oxygen from the surface air, fishes have gills. Gills are a series of membranes located on each side of the fish that function as respiratory organs. As water passes over this system of extremely fine gill membranes, the fishes absorb the oxygen from the water. The gills contain a network of fine blood vessels (capillaries) that take up the oxygen and diffuse it through the membranes. When fishes are taken out of water, they suffocate, because their gills collapse and they are unable to absorb oxygen.In many ways, the interior of the fish resembles that of many other animals. The digestive, circulatory, and nervous systems are very similar to those of other vertebrates. However, what really makes a fish different from other animals is its respiratory system. \n\n\n\nA fish’s respiratory system is determined primarily by the fact that it spends its entire life in water. Unlike the marine mammals such as whales, a fish has evolved in such a way as to not require frequent trips to the surface to breathe air. Fish have developed gills, on which they rely for the oxygen necessary for a fish’s limited metabolism. \n\nMany animals have gills at some stage of their life (even humans have them at an early stage of their development in the womb), but fish retained these gills and they are still a functional part of their anatomy. Fish use their gills to extract oxygen from their watery environment. The process starts with the fish’s mouth, which is how the fish takes in water. When a fish opens and closes its mouth, it is actually pumping water back through the gills and is thus breathing. Most fish have an effective pumping system that involves the mouth and the outer cover of the gills, called the operculum. When the fish’s mouth opens, the operculum closes, drawing water into the fish’s mouth. When the fish closes its mouth, the operculum opens, allowing fresh water to cross the gills. Other fish have a less effective pumping system, requiring them to swim constantly to keep fresh, oxygenated water flowing over the gills. These types of fish, such as tuna, generally swim with their mouths partly open. Incidentally, while many fish have nostrils, the nostrils are used only for a sense of smell, and play no part in respiration. \n\nOnce through the mouth, the water continues past structures called gill rakers. The gill rakers are essentially a filter system for the gills, straining the water to sift out floating food particles or foreign material. After passing through the gill rakers, the water continues through the gill arches and actually passes over the gills, which are suspended between the mouth cavity and the operculum. Each gill is made of two rows of gill filaments, which are extremely thin membranes sticking out into the water flow. Each of the gill filaments is composed of rows upon rows of lamellae, which are thin, disc-like membranes loaded with a capillary network. The water flows across the lamellae, and oxygen and carbon dioxide are exchanged directly across the capillary membrane. The capillaries are situated to take best advantage of the water flow; fish can actually extract up to 85% of available oxygen out of the water. Since water contains only 2-5% of the available oxygen that air at sea level does, such a high efficiency is extremely important. \n\nFrom the gills, the deoxygenated water passes out the operculum, and the oxygenated blood joins the circulatory system. Despite the efficiency, some fish require more oxygen than others. This helps to explain why some fish thrive in specific habitats. For example, trout prefer northern streams because the cool water of the streams tends to retain dissolved oxygen, and the active trout need the extra oxygen. Carp, on the other hand, are sluggish and do not need as much oxygen, which is why carp can thrive in warm, relatively stagnant ponds, such as ornamental ponds. Goldfish, unlike most f
1017954
I can show you a website that's a little technical, but should help.\n\nThe basic answer is, not really.  Most lizards are designed not to waste water, so they don't "pee" in the same sense a dog or a cat does.
6706
Some spiders do drink water as well as getting the fluids from prey.  Other spiders (like red-backs) don't drink water. If a spider has gone a while (sorry don't know how long) without water, it will approach a drop of water or dew drop and drink from it.
108061
Because fishes are cold blooded animals....sweating is a way for regulating temperature that is often employed by mammals.
341778
"Osmoregulation is the control of the levels of water and mineral salts in the blood"\n\nTherefore I say why not in fish?  They have blood and their blood also needs to have it levels regulated so it makes perfect sense. If you do not believe me here ya go :D\n\nWithout osmoregulation fish will die \n\nOsmoregulation is the control of the concentration of body fluids. If a fish is unable to regulate the effects of osmosis it will die. Clearly, osmoregulation is a vital function affecting all aspects of fish health.\n\nOsmosis, diffusion and fish health\n\nIf we look at the structure of the gill or gut under a powerful microscope we would see the tissue that lines these structures, the epithelium, is very thin, usually only one cell thick. Such areas are rich in blood vessels with very thin walls. The combined thickness of epithelium and blood vessels is less than the size of a full stop. The structure and thinness of these areas means that the minute particles whizzing around in the water (and blood) can pass through the epithelium and blood vessels with relative ease; in fact in many cases it is as if there wasn't any barrier at all!
1184568
With the exception of lungfish, most fish don't last long out of water because they can't breathe.  They die within minutes As well, they can't move at all so they are sitting prey for predators. In hot weather, they also dry out quickly.
698474
Gills are poor for terrestrial organisms because gills absorb dissolved oxygen in water by direct diffusion through the blood vessels in the gills.  In the air gills would not be able to diffuse oxygen through the blood vessels and much water would be lost through the gill blood vessels.  Pretty much this would cause dehydration in an organism quickly.
542858
Quick answer...one has a high salt content and the other does not.  Longer answer...when looking at salt and freshwater, it depends on the content of salt in the water.  Saltwater wetlands are usually along a sea or ocean, or along a tributary leading to them.  The salt content from teh ocean seeps up the river and hits the wetlands.  Freshwater wetlands are unsalanized and contain little or no salt.  This water supports freshwater fish and is a great watering spot for mammels and animals who need fresh (not ocean) water.
170207
why dont chickens pee
555268
OK a'lot of u don't no anything about catfish! It just depends on what catfish your dealing with and the conditions.  Some catfish in Africa can survive months without water, walking catfish have the capability of breathing oxygen (Bowfin are like this as well) they have something like a lung and this lung has chambers capable of taking in oxygen.  But these fish still need water in order to survive. I was fishing and caught these bullheads (small catfish) we accidently forgot one and this was in the afternoon when I returned the following day around 5-6pm it was still breathing I placed it back into the water and swimmed away.  CONDITIONS: The ground has to be moist or wet/muddy (keeps them cool) and theres a small amount of oxygen in the rain drops, moist ground, or mud.  If it's sunny and hot these fish wont live long (due to the slime drying out) and the slime makes them swim fast/quicker, scent (to find mates), and protects from diseases/viruses.
539761
It because fish produce ammonia which dissolves to form ammonia solution. The ammonia solution is basic thus it increases the pH of water in the aquarium.
541290
Carp can change its gill structure by having a lack of protruding lamellae (primary site for gas exchange) for survival in anoxic (without or limited oxigen) water. Therefore, they can breath air and forget about its oxigen consumption for around a month if they want.