<P> Lake Superior has fewer dissolved nutrients relative to its water volume than the other Great Lakes and so is less productive in terms of fish populations and is an oligotrophic lake . This is a result of the underdeveloped soils found in its relatively small watershed . However, nitrate concentrations in the lake have been continuously rising for more than a century . They are still much lower than levels considered dangerous to human health; but this steady, long - term rise is an unusual record of environmental nitrogen buildup . It may relate to anthropogenic alternations to the regional nitrogen cycle, but researchers are still unsure of the causes of this change to the lake's ecology . </P> <P> As for other Great Lakes fish, populations have also been affected by the accidental or intentional introduction of foreign species such as the sea lamprey and Eurasian ruffe . Accidental introductions have occurred in part by the removal of natural barriers to navigation between the Great Lakes . Overfishing has also been a factor in the decline of fish populations . </P>

What is the deepest lake in the great lakes