Complex sentence: As above mentioned, the island was historically targeted by whalers to target whales including North Pacific right whales and fin whales in adjacent sea, and cetaceans such as minke whales and dolphins may appear around the island.
Split into simpler sentences: As above mentioned, the island was historically targeted by whalers to target whales including North Pacific right whales. Fin whales were also commonly observed historically, and cetaceans such as minke whales and dolphins may appear around the island.