One major way to tell is whether they would live in a lake (freshwater) or in the ocean (saltwater).
Springs are simply freshwater. But some of the fish, if any, in springs are salt and fresh water fish. Think of ponds and rivers and lakes. Those are all freshwater too. One more fact that I have to tell you is that water should be stored in a cool, dark, and dry place.
the amount of salt dissolved in the water
The biggest fresh water fish is the great sturgeon reaching 23 feet in total
The density of a salt water solution compared against the densities of "pure" water and salt provides an approximate value of the ratio of water to salt in the mixture.
All I can tell you is water, rocks, and dirt. Sorry if that is not enough
Salt is the solute. Water is the solvent. Salt water is the solution. This solution is sometimes called a saline solution.
taste
You can evaporate it.
taste it
By the salinity or salt level in the water which can be measure by a number of devices most commonly the hydrometer or refractometer.
Ocean. The ship will ride higher in salt water than fresh in water. There is a load line on the side of ships to tell you how deep you can load the ship. You can load the ship deeper if it is in fresh water because it will come up when it gets to the ocean.
The answer is: salt is soluble in water.