DUN Magazine Print - Spring Summer 2017

science I have always been told that my mind over-analyzes my actions, however in this case, I think it serves as a great reminder. A reminder to every angler that how we handle our fish can severely influence their life after. We have all felt it. The soft and slick body of a trout as we try to release its fragile jaw from the fly. Have you ever questioned what that slickness really is? Or does?

Fish mucus, often referred to as “fish slime,” is produced in the goblet cells of the epidermis layer of the fish (outermost layer of skin). Humans also produce mucous, however, ours serves a different function in the body. Human mucous is produced in the goblet cells of the mucous membranes that line our respiratory, intestinal, urinary and reproductive passages. The coating serves as a lubricant for the passage of materials, while also keeping the areas healthy by maintaining a moist environment. As in humans, the mucus created by fish goblet cells also serves to maintain conditions, however, it is present externally on the surface of the fish.

The mucus, present in all fish, is a combination of compounds that aid in protecting the fish, much like our skin protects us. Each community of fish has its own chemical make-up within the mucus, because factors that are produced are specific to the species and environment in which it lives. The mucus is a mechanical defense against parasites and pathogens, blocking them from entering the body. There have also been studies that show osmoregulatory and locomotive functions (Van Oosten 1957, Rosen and Cornford 1971). Osmoregulation is crucial for fish to maintain osmotic pressure within their cells while in the water. By regulating the concentrations of ions flowing in and out of the body, the fish can keep a correct balance between its internal concentrations and the concentrations found in the water column. Without the regulation, these ions would accumulate and become toxic for organs such as the kidneys and their skin. This mucus allows proper release and uptake of ions while also providing a barrier for unwanted molecules. Because the chemical make-up of the mucus varies along genetic and environmental conditions, research is very interested in looking at specific compounds that aid in protecting some of the most economically important species, such as the rainbow trout.