Restoring Ups and Downs on the Mississippi
(pg 2 of 11)
In the 1930s the Corps built most of the locks
and dams at 29 locations to create a 9-foot-deep
channel from Minneapolis to St. Louis. The
structures cut the river into sections, creating a
series of deep pools for barges but also preventing
the migration of fish.
Unable to ascend the river to spawn, the
skipjack herring disappeared from the river above
Keokuk, Iowa. The ebony shell, once the upper
Mississippi's dominant mussel, nearly disappeared
as well because its larvae hitchhike in the gills
of only one fish, the skipjack herring.
Top: Skipjack herring
disappeared from the Mississippi river due to
habitat loss after the river was channelized. Left:
Ebony shell mussels then became threatened as well
because their larvae hitchhike in the gills of only
one fish, the skipjack herring.