Lost At Sea
By Mary Jane Schramm
Amid swirling kelp fronds in sunlit shallows, the massive creature grazed placidly, her enormous bulk all but invisible beneath the waves, a calf tucked snugly into her side. Periodically their heads broke the surface, nostrils flared to take a few breaths. The mother displayed a broad, dark, pebbly expanse of back and a flat whale-like tail; and, indeed, she was the size of a short and very unstreamlined whale. She had gathered within her herd of 20 or more intimates, to socialize, nurse, and feed on kelp and sea grasses in the cold nearshore waters of the subarctic North Pacific. They were concentrated around the Commander Islands off Russia, in the western Aleutian chain, but sadly, their feeding grounds lay along the route of Alaska-bound Russian fur hunters, and the sailors knew just where to find them. Unlike the highly prized sea otters they sought, these animals were not their primary targets. But, on long expeditions, the beef-like meat and blubber of these “sea cows’’ nicely augmented ship’s stores.
Seagoing Potatoes: The now-extinct Steller’s sea cow, Hydrodamalis gigas, of the order Sirenia, is most closely related to the modern dugong of the South Pacific and Indian Oceans, and the manatee of the tropical Atlantic. A former Floridian, I regarded manatees as large, aquatic spuds, which they greatly resemble. However, Steller’s subjects were triple their size, up to 30 feet long and hugely rotund, weighing 11 tons.
Few records exist of their ecology and behaviors except as documented by German biologist and explorer Georg Wilhelm Steller who scientifically described the species in 1741 – just 28 years before the species disappeared forever, in 1768.
Witness To Extinction: Fossils from the Pleistocene Epoch Ice Age that ended around 14,000 years ago, indicate Steller’s sea cows inhabited coastal waters from Baja California north to the Bering Sea, and south along the Japanese coast. Their huge size and other adaptations to a cold-water regimen enabled some to endure subarctic conditions where kelp thrived. Paleolithic hunters may have had some impacts, and firsthand accounts note that Aleut and Yupik hunters easily paddled and waded into the shallows among herds of unwary sea cows. By the time Europeans arrived, sea cows may have been in decline, but the Pacific maritime fur trade administered the final disastrous blow, and it was two-fold.
Apart from direct hunting, scientists believe the sudden depletion of the Stellers’ food supply, kelp, could have tipped them into an irreversible downward spiral. The fur hunters devastated otter populations. Sea otters eat sea urchins, which left unchecked devastate entire kelp forests and algae beds, leaving the sea cows to starve. “Disappeared” kelp forests and sea urchin barrens along the Sonoma and Mendocino coasts show how even a few species’ loss can catastrophically disrupt ecosystems.
Du-Gone? The International Union for the Conservation of Nature (IUCN) Red List of Threatened Species lists the Steller’s sea cow’s extant relatives, dugongs and manatees, as vulnerable or endangered. IUCN states, “Dugongs are represented by diminished remnant populations, many of which are close to extinction.” Habitat loss, vessel and fisheries interactions, and climate change take heavy tolls.
Deep Thoughts: It’s important to anticipate potential impacts our species may have, as we are now engaged in exploring and exploiting new ocean frontiers, as in deep sea mining. But we must pursue these initiatives with a precautionary approach. Like a Jenga tower, it’s hard to say what piece, once removed, could cause the structure to collapse. A solid first step is to conduct baseline studies of these habitats, as our local national marine sanctuaries are doing; see more at https://farallones.noaa.gov/science/seafloor.html.
