Complex sentence: Loss of habitat is thought to be responsible for its decline; much of the Missouri River drainage system has been channeled and dammed, reducing the gravel deposits and slow-moving side channels that are its favored spawning areas.
Split into simpler sentences: Loss of habitat is thought to be responsible for its decline. Much of the Missouri River drainage system has been channeled and dammed, reducing the gravel deposits and slow-moving side channels that are its favored spawning areas.