Murky, Green-Colored Water
Description: Murky, green-colored water that looks like green paint on the windward shore; unpleasant odor
Analysis: Algae. Algae are microscopic plant-like organisms that are natural components of lakes and streams. When high nutrient concentrations occur, algae become so abundant that the water becomes murky. People should avoid swimming in algae blooms because toxins in some algae cause skin irritation. Consumption of water by livestock and other animals such as pets during an algal bloom can result in intestinal distress and, in extreme cases, death.
Description: Yellow-green dust on the lake in early summer
Analysis: Pollen from nearby trees. The pollen might look similar to algae, but pollen is more yellow and dust-like and floats on the surface. Over time the pollen will become waterlogged and sink from sight. Pollen usually has little effect on water quality.
Red, Itchy Rash
Description: Red, itchy rash on swimmers soon after coming out of the water
Analysis: Swimmer’s itch. Swimmer’s itch is caused by a parasite that typically uses waterfowl and snails as hosts, but can irritate humans. The swimmer may notice a prickling sensation after getting out of the water and may develop red spots and swelling that can last a week or more. To prevent swimmer’s itch, towel off vigorously or take a shower immediately after coming out of the water– especially in mid to late summer when the parasite is most prevalent. It is not dangerous or contagious, but can be very uncomfortable.
Description: Dead fish in the water or on the shore
Analysis: A few dead fish along the shore is not significant and may result from natural causes, such as spawning, or bacterial infection from warm summer water. Numerous dead fish (dozens or more) or dead fish of more than one species is a cause for concern. Contact your regional Montana Fish, Wildlife & Parks office immediately to report the problem.
Description: Foam “soap suds” along the shore
Analysis: Foam along the shore does not necessarily indicate pollution from laundry waste. Foam is created when the surface tension of water is reduced and air is introduced. This causes bubbles. Many natural organic compounds will reduce surface tension and when these compounds are mixed with air by wind and currents, they produce foam. Natural foam has a somewhat earthy or fishy smell while detergent foam will smell of perfume.
Green Cotton Candy
Description: Green, cotton candy-like clouds in shallow waters
Analysis: Filamentous algae. It is common in some lakes and may not indicate a water quality problem. These clouds may appear after heavy run-off in the spring or following a long, hot spell in the summer. However, localized concentrations may indicate a pollution source nearby.
Description: Dark cloud in the water accompanied by an oily sheen.
Analysis: The cloud may be insect cases left behind from a hatch of aquatic insects, which hatch any time during the open water season. Wind often concentrates the cases along the shore, and as they decompose, an oily film can form on the water’s surface. Dark oily clouds can also occur near decomposing leaves, typically in the fall.
Description: Flat, worm-like animals attached to skin.
Analysis: Leeches. Leeches are found in shallow, protected waters and are active on hot summer days and at night. They are attracted to water disturbance around docks and swimming areas. The best way to avoid leeches is to swim in deep waters.
Montana’s Native Fish
Adapted from Montana Fish, Wildlife & Parks
As a group, all 56 native Montana fish still inhabit state waters, but some are facing a long fight for survival. Most of our best-known fish – rainbow trout, brown trout, largemouth bass, and walleye – are not native to Montana, but were introduced by newcomers as sport fish.
Montana’s native fish adapted to a life in mountain and prairie streams over thousands of years – enduring wild spring floods, summer droughts, and long, cold winters.
As new settlers changed Montana’s landscape, the cycle of life changed for Montana’s native fish as well. The eventual planned and unplanned introductions of non-native fish also added new challenges to our native fishes’ struggle to survive in Montana waters.
Like a family heirloom passed from generation to generation, Montana’s native cutthroat trout are among the treasures that make Montana such a special place. Montana’s native fish are Nature’s Keepers and it’s up to all of us to keep it that way.
Return to Chapter 4 Table of Contents