Complex sentence: Herring feed on phytoplankton and as they mature they start to consume larger organisms.Herring also feed on zooplankton, tiny animals that are found in oceanic surface waters, and small fish and fish larvae.
Split into simpler sentences: Herring feed on phytoplankton, and as they mature, they start to consume larger organisms. They also feed on zooplankton, tiny animals found in oceanic surface waters, and small fish and fish larvae.