Daily Press

THE SLIME ON FISHES.

Common to All Species and Essential to Their Existence.

A fish just taken from the water, if handled, is found to be slippery and coated with slime. All fishes, the meanest and the noblest, killifish and shark, shad, salmon and trout, wear this slime. They could not exist without it.

The slime is secreted usually in a continuous series of ducts, with numerous openings arranged in a line extending along the side of the fish. Some fishes have one line on a side, some have five or six. The lines may be plainly visible, and in some cases appear to be a marking on the fish. More often they are not observable at all.

Some fishes store this secretion in pores distributed over the whole surface of the body, the larger number, however, in pores in lateral lines. There are also pores for the secretion of mucus, or slime, in the fish's head.

The slime is exuded through the divisions between the scales to the outer part of the body, over which it spreads, forming a sort of outer skin or covering, transparent and having elasticity and tenacity and often considerable body. It would not be remarkable for a fair sized fish, say a fish of two pounds weight, to have a coating of slime a thirty-second of an inch in thickness. Fishes vary greatly in the amount of slime which they secrete.

The eel will suggest itself as one very slimy.

The fish's slimy coating reduces its friction when in motion and helps to increase its speed. Its skin is protecting the scales from injury, being of sufficient substance to serve in some measure as a cushion. The slimy covering makes the fish hard to hold and so enables it the more readily to escape from its enemies. It is sometimes repugnant to other fishes, which are repelled by its odor. It is the slime from the fishes handled that makes the angler "smell fishy," as the expression goes.

A most important function of the fish's slimy coating is to protect it from the attacks of fungus, a form of plant life found in all waters, salt and fresh, including the purest. The slime covers the entire exterior surface of the fish, including the fins. Fungus does not attach to the slime, but if the fish were to be injured so that there was upon it some spot uncovered by the slime upon that spot some minute fragment of fungus, so small as to be scarcely more than visible, would be likely to lodge. Once lodged the fungus is reproduced very fast.

Fish sometimes recover from attacks of fungus, but much more often they do not. The fungus displaces the skin, inflammation is set up, and the place attacked becomes practically a sore. With its continued growth the fungus may cover the side of the fish and extend over the gills and finally kill it.