Immerse yourself in the secrets of fish colors and shades

Brian Van Acker raised a question about the colors of fish that I receive on some regular basis.

“I caught these two catfish (on a June weekend) in two different bodies of water,” he said on Twitter. “The first was 25 inches, 7 pounds; The second is 24 inches and you guessed it 5 pounds. Their colors are very different. What causes this? Different bodies of water? Age of the fish?

Chris Taylor, Ph.D. “The light-colored fish (top) may actually be a white catfish, while the darker fish (bottom) is a channel catfish,” the curator of fish and crustaceans at the Illinois Natural History Survey emailed. “In Illinois and not native to the state. They have been stored in various locations for the past five (years).”

Brian Van Acker holds a beautiful catfish.

Regarding the broader question of fish coloration, Taylor emailed:

Fish use coloring for two main purposes: communication and evading predators. As for your question about why some individuals of the same species have different colors in the Illinois species, it is mostly due to communication. In most species, males have the most prominent colors, and these males use those colors to increase their attractiveness to females. Just as a lion with a large mane is more suitable as a mate, a male fish with bright colors is more suitable. The male’s color is also used to make other males feel that they are the “top dog.” In a lake full of fish, there will be a wide range of sizes and health (fitness) in males of a single species.

However, you were also right in saying that depth and habitat can change color slightly. Less light penetrates to deeper depths, and water clarity may vary in a large (body of water) or stream. Depending on depth or clarity, fish may need to increase or decrease the intensity of their color in order to be noticed.

She also asked how fish colors change. Put on your science hats for this.

“This gets complicated very quickly, but in short, fish have cells called chromatophores near the surface of the skin that are very irregular in shape,” Taylor wrote via email. “There are different colored pigments (red, green, yellow) in the chromatophores, and these pigments are very small. Either by using hormones or nerves, fish can either pack pigments into a small, tight group within the chromatophore to brighten that color, or they can spread those pigments across the chromatophore to increase the intensity Color: Hormonal control of coloration can result in color changes that may last for several months. This is why breeding males look different from non-breeding males.

“A final point is that body size can affect colour. Larger individuals can have more pigment, and therefore darker or brighter colours.

“Color change resulting from nerve function usually occurs very quickly and usually involves darkening of different areas of the body. For example, the sudden appearance of a predator can cause a fish to quickly darken the sides of the body to help it become more opaque in color and blend into areas Background or plants.

Wild things

Chris Strand He encountered his first river otter Saturday while fishing in the Des Plaines River. “To be honest, it looked like the Loch Ness Monster!” He sent a message. “Very funny. By the way his head, then his body, then his tail turns around in the water, I see how people make mistakes. … I couldn’t find a hen of the woods mushroom on Friday, but I did find a hen of the woods mushroom.

Pour stray

Bear season really feels like your shoe is slipping on a rock while crossing the river.

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