What caused the Aleutian sea otter collapse?

What caused the Aleutian sea otter collapse?

The leading hypothesis for the disappearance of sea otters is that killer whales have begun preying on the animal as great whales, Steller sea lions and harbor seals have become less abundant. When the sea otter population dwindled, sea urchin numbers grew.

What happened to the Aleutian Island sea otters?

They aren’t sick. They have vanished. Throughout the Gulf of Alaska and probably the Bering Sea, too, the balance of prey and predator has been upended, a transformation so extreme it’s called a “regime shift.” Waters once brimming with seals, otters, and king crab are now dominated by sharks, pollock, and urchins.

What is causing the rapid loss of sea otters in Alaska?

The team then set out to determine if the decline in sea otters and the rise of sea urchins in combination with climate change was the reason for this loss. “Warming of sea water in the last half century has accelerated the rate of grazing in this ecosystem,” he said.

Why have sea otters declined in recent years along the Alaska coast?

Since the mid-1980s, the sea otter population in the southwestern population stock in Alaska has declined 56-68%. Decreased kelp and increased sea urchin numbers in the nearshore ecosystem in the Aleutian archipelago are evident as a result of precipitous population declines of sea otters.

What are three future threats facing the Aleutian sea otters?

Humans are the biggest threat to sea otter populations. Direct conflict with humans, through shootings, fishing gear entanglements and boat strikes, take a toll on sea otters, but oil spills, pollution, disease and loss of kelp pose major threats.

What caused killer whales to start eating sea otters?

Williams says the answer turned out to be a simple one. Orcas were eating otters because the really big whales they used to eat were nearly wiped out by commercial whalers back in the 1950s. When the big whales got hard to find, Williams says, the orcas switched to big, stellar sea lions and then to medium-sized seals.

Why did the sea otter population decline in the 1980’s 1990’s?

The population declined to a uniformly low density in the archipelago, suggesting a common and geographically widespread cause. These data are in general agreement with the hypothesis of increased predation on sea otters.

How long have northern sea otters been endangered?

Historically, an estimated 150,000 to 300,000 sea otters occurred in coastal waters of the North Pacific Ocean. These populations were decimated by almost two centuries of commercial hunting. Since the 1980s, most northern sea otter populations have continued to recover.

What would happen if sea otters went extinct?

As top predators, sea otters are critical to maintaining the balance of nearshore ecosystems, such as kelp forests, embayments and estuaries. Without sea otters, sea urchins can overpopulate the sea floor and devour the kelp forests that provide cover and food for many other marine animals.

How many sea otters are left 2021?

There are only about 3,000 southern sea otters left in the wild today.

Are otters endangered 2021?

IUCN/The World Conservation Union lists the marine, giant, southern river, and sea otters are listed as “endangered” (species has a very high risk of extinction).

How did the disappearance of the sea otters influence the coastal marine ecosystem?

The decline in sea otters has allowed their primary prey, sea urchins, to increase in number and strip coastal kelp forests over large areas. Overexploitation of certain North Pacific and Bering Sea fisheries may have initiated this cascade of ecological effects, Estes said.

Why are sea otters disappearing from Alaska’s Aleutian Islands?

Against the backdrop of climate change, the delicate underwater ecology of Alaska’s Aleutian Islands is hurting from declines in otters. Sea otters, which can eat nearly 1,000 sea urchins a day, have seen their numbers along Alaska’s Aleutian Islands shrink by 90 percent in recent decades.

What are the threats to sea otters?

Threats to sea otters include predation, overharvest, fishery interactions, disease, and oil spill. There is concern, particularly in the Aleutian Islands, that increased predation by killer whales may be leading to declines in sea otter populations.

Are sea otters in decline in Kodiak Island?

A less precipitous decline occurred over that same period in the eastern Aleutian Islands. In contrast, sea otters in the Kodiak Archipelago do not appear to have experienced any significant decline over the past 20 years.

Are there sea otters in Southcentral Alaska?

The Southcentral and Southeast Alaska stocks continue to grow or have stabilized and are not listed under the ESA. All three stocks in Alaska are protected under the MMPA. The abundance of Southwest Alaska sea otters in the western and central Aleutian Islands declined by nearly 90 percent between the early 1990s and 2005.