By definition, fish are animals that live in water, have gills and lack limbs. They are also chordates, which means they have a backbone-like structure that provides support for the body and acts as an anchor for the major muscles.
Animals that live in water but have limbs rather than fins are not fish, but rather amphibians or reptiles. Most fish are cold-blooded, but there are a few exceptions to this generalization, including tuna, swordfish and certain types of sharks. Some animals that have the word "fish" in their name are not actually fish. For example, jellyfish are invertebrates, not chordates, and do not meet the definition of a fish.Learn More
How long a fish can live out of water depends on the species of fish, as some fish can survive for up to a few days while others can only survive for minutes. The fish that can survive for a few days without water do so by breathing the air or by absorbing it through skin.Full Answer >
Tap water must sit out and be put through aeration practices for a minimum of 12 hours before fish can be put into the water. The reason for this is that all tap water has chlorine in it and chlorine is harmful to fish.Full Answer >
Goldfish, as a result of having gills, require oxygen in order to survive. Encyclopædia Britannica references that all fish have gills, which are used to exchange oxygen and carbon dioxide with the surrounding water. Goldfish are members of the carp family, and lived in ponds in Asia before domestication.Full Answer >
Gill rakers are bony or cartilaginous outgrowths that project from the branchial arch of fish and assist in feeding by preventing stray particles or loose pieces from exiting through the gills. The size and arrangement of the gill rakers can signify what the fish eats.Full Answer >