Slimecoat what is it Well- it is a mucous created by the continal replacement of glandular cells know in the fishes skin that produce a glycoprotein which is called mucin. This when mixed with water forms the mucus that makes up the slime coat of fish.Fish with poorly developed scales tend to produce more of this slime coat.. The slime coat does three basic things- it reduces turbulence for the fish when swimming by smotthing over the areas between the fishes scales-it helps regulate the internal/external ionic balance and the efficiecy of gases exchanged through the skins surface-ie-osmoregullation and it provides a slipery surface that in it's sloughing off prevents bacteria from attching themselves to the skin. Bacteria is simply washed away from the skin with this process. It also aids in acting as a wound bandage. Pretty important stuff........In some fish it retains moisture(lungfish) feeds fry(discus and some asian cat fish)) and can be toxic for a defence mechanicism and form a cocoon as in marine parrotfish for sleeping.It is the nest building material in labyrinth fishes and functions as a as a chemical alarm through the water from panic syndrome or injury.Stressed fish have a change in thier slime coat-either too much or too little of this protection will kill a fish.
While it isn't exactly the same, you can think of it as a layer of skin. If something removed all of your skin, you'd be more prone to infection as well.