They are usually either weedy or subject to frequent algae blooms, or both. Eutrophic lakes often support large fish populations, but are also susceptible to oxygen depletion. Small, shallow, eutrophic lakes are especially vulnerable to winterkill which can reduce the number and variety of fish. Rough fish are commonly found in eutrophic lakes. Mesotrophic lakes lie between the oligotrophic and eutrophic stages.
Researchers use various methods to calculate the trophic state of lakes.
At the middle, or deepest spot, of the lake, rinse the TP bottle and cap 3 times with lake water at the surface. Be sure not to put your fingers inside the bottle or the cap, and to empty the rinse water on the other side of the boat. Then dip the bottle upside down in the water to elbow length, turn it upside right, and wait until there are no more air bubbles coming out of the bottle. Squeeze the bottle and cap it simultaneously. Store in cooler until sample can be frozen.