The reason is that numerous environmental conditions vary among lakes, including altitudes and sizes, amount of exposure to the sun, and localized rainfall. Hence, during any given year, some lakes may be suitable for a species, such as the spotted frog, to produce surviving young, whereas other lakes are not. Yet in other years, this year's suitable lakes may become unsuitable and vice versa. Programs to stock mountain lakes of the West with trout to enhance recreational fishing have been going on throughout most of this century by state and federal programs. The environmental problem with the fish stocking programs is that many high mountain lakes have always had frogs but had never before had fish.
Fish eat tadpoles.
In a clear mountain lake, not one is likely to escape the eye of a trout. You do the math for where all this will lead from the viewpoint of the frogs. Studies are continuing, and a positive collaboration is ongoing between the researchers and the wildlife agency in charge of the trout. The agency is considering the habitat requirements of native aquatic organisms, as well as recreational angling, in redesigning its stocking program in order to return the system to a more natural one. The ecoparadigm that the only good mountain lake is one with trout has been challenged.