Complex sentence: Accordingly, one can consider 1835 as a good year to use as a baseline for the historic pn the single decade of 1840-49, between 21,000-30,000 northern right whales may have been killed in the North Pacific, Sea of Okhotsk and Bering Sea.
Split into simpler sentences: Accordingly, one can consider 1835 as a good year to use as a baseline for the historic population. In the single decade of 1840-49, between 21,000-30,000 northern right whales may have been killed in the North Pacific, Sea of Okhotsk and Bering Sea.