Gray Whale

Even if you see only their “blow” or waterspout, gray whales are distinctive. They have two blow-holes rather than one, and from the right viewing angle their twin spouts form a distinctive heart shape.

KODIAK — Everybody eats. I thought writing about nutrition would be easy, especially since I have lately spent quite some effort learning more about what foods energize and what foods actually zap us of energy. Hours later, I found myself still staring at a blank page after going down several internet rabbit holes. 

What triggered the idea to write about food was a flyer sent out by the Alaska Regional National Oceanic and Atmospheric Administration Fisheries Office concerning the stranding of unusually large numbers of gray whales along their migration route from Mexico all the way to the Bering Sea. I also heard that people have been seeing a group of gray whales in Pasagshak very close to the beach; some noted that the whales looked emaciated. Indeed, the one thing all the more than 160 whales found dead along their migratory route had in common was that they seemed malnourished.

In wondering why all those whales are starving, I first researched water temperatures in the North Pacific and in their wintering grounds in Mexico. I was reminded of “the Blob,” a mass of warm water that caused thousands of sea lions to starve in California because the fish they rely on were avoiding the nutrient depleted warm water. While the North Pacific is scary warm this year compared to its average temperature, that may not be what ails the gray whales. Gray whales and humpback whales alike eat almost exclusively in the summer months when they are in Alaska and live off their own fat reserves during the months they spend away from Alaska in warmer, less productive waters. 

Gray whales primarily eat crustaceans, such as amphipods, that live in or on the ocean sediment. To do this, the whales roll onto their side and plow through the ocean bottom mud with their jaw, filtering the scooped mud soup through the baleen on their upper jaw. While there has been a group of gray whales that stay around Kodiak for their summer feeding, most of the whales keep swimming north into the Bering Sea. 

Historically, the Bering Sea shelf is home to large numbers of these crustaceans, which feed on anything that sinks to the ocean bottom. Usually, the ice edge in the Bering Sea was not far from the shelf edge. Under the ice, ice algae grow in the spring. Then, when the ice retreats, some of those algae sink to the bottom, feeding the crustaceans, which in turn feed the whales. 

At the risk of writing something that I have no scientific evidence for, I am going to put forward a theory: I think that the gray whales may be malnourished because last year the mud on the Bering Sea shelf was lacking the huge load of crustaceans. If they did not eat enough last summer, their fat reserves did not quite last them through the 5,000 mile swim south, the winter and then the 5,000-mile return journey. 

Why do I think there was not enough food last year? Because those crustaceans feed on whatever falls down from above. Usually, sea ice is associated with ice algae. Also, when the sea ice retreats in spring, the ice edge has nutrient loaded water that triggers a phytoplankton bloom. When this bloom runs out of nutrients and the cells die off, they sink to the bottom, feeding the crustaceans in the mud. However, the ice edge was much farther out last year. Last week, Science Magazine reported that “in winter 2018, ice cover in the Bering Sea reached its lowest extent since constant satellite monitoring began in 1978.” 

The Bering Sea shelf is a large area of ocean bottom that is relatively shallow and usually highly productive. At the shelf edge, the water depth rapidly increases. So, I am speculating that the rain of dead phytoplankton fell over the deep part of the Bering Sea and missed the shelf. You might say the food fell under the table instead of on it.

Please don’t misrepresent this as science, because it is just my personal, educated guess. A theory like this would, in the science world, be the start for a research proposal, where it could be tested and proven. 

Since I am not in the business of Bering Sea shelf research, I will leave that to someone else (you are welcome). Meanwhile, I hope the whales find food in Alaska this year — I much prefer to see these amazing giants well and alive.

Switgard Duesterloh runs the Ocean Science Discovery Program, which invites school classes to hands-on place based Marine Science learning units. She is in the process of expanding the program to include more opportunities for summer learning experiences for kids, youth, families and adult travelers. For more info or to contact her about Amazing Nature email switgard@gci.net.

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