The Russians , therefore , advanced to the Northwest Coast only after the superior varieties of sea otters were depleted , around 1788 .
Their fur was thicker , glossier , and blacker than those of sea otters on the Pacific Northwest Coast and California .
The Russians , therefore , advanced to the Pacific Northwest Coast   only after the superior varieties of sea otters were depleted , around 1788 .
Their fur was thicker , glossier , and blacker than those of sea otters on the Pacific Northwest Coast and California .