1. Around 1900 the first dams were built on the Muskegon river, and this immediately cause a problem in the ecosystem by being a blockade for the movement of the water species, as well as causing higher mortality by killing them in the turbines.
2. By 1950 more dams were built, and the there were even more blockades on the way of the water species, so their movement was restricted even more, the mortality rates skyrocketed because of the disposing of the oxygen, temperature change, river flows changing etc.
3. Even though the scientists miss information from the period before the dams were built, since the information have started to be gathered it has been very obvious that the main factor for ruining the ecosystems on the Muskegon river are the dams by causing all sorts of changes in the water.