Complex sentence: The Delta is home to approximately 22 species of fish including the Delta smelt, a key indicator species for the health of the Delta's ecosystem, was found in 2004 to be on the edge of extinction.
Split into simpler sentences: The Delta is home to approximately 22 species of fish including the Delta smelt, a key indicator species for the health of the Delta's ecosystem. In 2004, the Delta smelt was found to be on the edge of extinction.