Some dams can block the upstream migration of
numerous fish species. In many areas where dams
are built, spawning habitat for fish is lost because the fish can
no longer get to that habitat.
There are some ways in which fish migration is
possible, even in areas where dams have been built. Fish
passages are being added where many dams are located.
These allow fish to migrate further upstream into areas that were
not available to them after the dam was created.
The lake sturgeon, however, cannot use fish passages
to bypass dams because sturgeon are too big. This is one factor
that contributed to the decline of the lake sturgeon. Much
of its original spawning habitat was lost due to the construction