Field Notes

April 8, 2019

The Scoop on Slime Coats

By Caitlin Yoder, education coordinator at the Lilly Center

If you have handled a fish, frog or salamander, you may recall feeling that slimy, slippery goo that coats their scales and skin. Most people have an initial negative response to this ooze known as a “slime coat”, but what most people do not know is that this layer of slime is vital for the health of the critter that it covers. If you have seen our new facilities in the Dr. Dane A. Miller Science Complex at Grace College, then you would have seen the display of slimy critters that call the Lilly Center home. All of our aquarium care processes are designed to protect and promote the slime coat of our fish and amphibian friends.   

Slime is vital for fish and amphibians to survive. Besides aiding the fish in drag resistance in swimming, the slime also protects them from parasites and infection. When germs or parasites try to attach themselves to the fish, they can’t because it’s too slippery, or they suffocate in the slime. Not to mention that the slime also contains medical qualities that are soothing to any wounds on the fish’s body. It’s like a built-in pharmacy that the fish can wear! There is even current research being done to isolate the slimes active ingredients for treatment in humans. You can read more about the study here.

So what effect does lake health and water quality have on a fish’s slime coat? Quite a bit, actually! The number one cause of deteriorated slime coats is stress, and the quality of the fish’s habitat has a lot to do with how stressed the fish population will be. When the water quality in a lake or stream is impaired, it greatly increases a fish’s stress response. Poor water quality is usually a result of imbalance in water chemistry such as pH, salinity, ammonia, dissolved oxygen, etc.

These levels are greatly affected by the nutrient levels and pollution from runoff.  There is a lot we can do as citizens to protect the water quality in our lakes and streams, and consequently the slime coats of the aquatic inhabitants. Good practices like reducing erosion from your property, properly disposing of household hazardous waste and yard clippings, and regularly maintaining your septic systems will help keep the water clean and reduce the stress levels on the fish populations that call them home. So next time you feel queasy about a slimy fish or frog, try and re-think how miraculous this natural protection really is!

Embrace the fun and function of slime by making this fish tank slime recipe from Elmer’s glue! Follow the link for instructions!