Complex sentence: Steller researched the wildlife of Bering Island while he was shipwrecked there; the animals on the island included relict populations of sea cows, sea otters, Steller sea lions, and northern fur seals.
Split into simpler sentences: Steller researched the wildlife of Bering Island while he was shipwrecked there. The animals on the island included relict populations of sea cows, sea otters, Steller sea lions, and northern fur seals.