Complex sentence: Cutthroat trout usually inhabit and spawn in small to moderately large, clear, well-oxygenated, shallow rivers with gravel bottoms and clear, cold, moderately deep lakes.
Split into simpler sentences: Cutthroat trout usually inhabit and spawn in small to moderately large, clear, well-oxygenated, shallow rivers with gravel bottoms. They also reproduce in clear, cold, moderately deep lakes.