If you have ever caught a fish you may have noticed they are slimy, which can make them hard to hold for a photo.

The slime is produced by the fish’s skin and has several purposes.

One is to protect the fish from bacteria, pollution and parasites, which could make the fish sick. The slime can also help heal a wound, like medicine we put on a cut. Scientists are even seeing what’s in fish slime to find out if there are chemicals humans could use for medicines.

The gooey substance also helps fish glide through the water easier, so they use less energy to swim, and may help them to squirm away from other fish or animals trying to eat them, like humans. Some fish even have poisons in their slime to help protect them.

Because the gunk is important to fish, anglers should keep them in the water as much as possible and wet their hands before picking a fish up. Nets with softer fibers can also help protect fish from losing their slimy coating. These are all important things to consider if you are going to let the fish go, but not if you are going to kill and eat the fish.

Catfish and northern pike are especially goopy fish. Some anglers don’t even like to catch them because of the slime. If you net one and want to eat it, the slime can be removed by swishing the fish around in a bucket of water. If that doesn’t work, special gloves can help you or an adult to hold the fish.

Even fish in aquariums have slime. It’s important for fish owners to keep their aquarium water clean and fresh to ensure their fish, and the fish’s goop, remain healthy.

— Brett French, french@billingsgazette.com