What I did on my summer vacation: I went and hung out with killer whales again.

And as you can see from the video at right -- a slideshow I put together over the weekend at camp, with a soundtrack featuring sounds I recorded -- it was something of a close encounter. It was the kind of experience that makes you wonder why we're searching for intelligent life on other planets when you have it in your own backyard.

It was also the kind of experience that makes you realize how we puny humans -- because believe me, we are puny compared to orcas, as you realize when you meet them up close -- hold their life-and-death fate in our thoughtless little hands.

We were simply sitting atop a kelp bed in our kayak -- me and Lisa and Fiona -- about 300 yards from shore when a pod of about 30 orcas (mostly the K pod) swam by on both sides of us.

I'd dropped a hydrophone down into the bed and Fiona and I listened in as they approached and then swam past. The most audible sounds, as you can hear, are their calls, which are seemingly how they communicate; the other sounds, much more subtle but almost as common, are the rat-a-tat-tat of their echolocation, which is how they see for dozens, perhaps hundreds, of yards underwater.

It's also how they locate their prey -- which, for these orcas, consists almost entirely of chinook salmon. They riddled the kelp bed with echolocation because they like to chase fish into and out of them, while only coming up around its edges. They also, as you can see, seemed to like draping themselves with kelp leaves and fronds.

Listening to them it was clear that, through both their calls and their sonar, they were working hard to find salmon. This year has reportedly been better than in years past. Yet the day after we saw these orcas, they headed out west into the open Pacific to try to find salmon there and were gone for the next four days.

These orcas are an officially listed endangered population, and the main reason is the salmon. NOAA's official recovery strategy, in assessing threats to the whales, lists "prey availability" as the top item. And things have become dire -- particularly elsewhere along the entire Pacific Coast.

The collapse of the California chinook runs resulted in an emergency suspension of the fishing season. The annual Yukon River chinook runs "just didn't show up."

While overfishing almost certainly is playing a role in this, it appears likely that a lot of the blame lies with a phenomenon that caused the 2005 collapse of the Pacific Ocean's coastal food web, in which thousands of sea birds died and likely killing the chinook that went to sea that year:

NOAA Fisheries Service oceanographer Bill Peterson said Monday the juvenile salmon that left their native rivers and entered the Pacific Ocean in 2005 found little food being transported by the California Current, which flows from the northern Pacific south along the West Coast.

The reason was that the jet stream had shifted to the south, delaying the spring onset of winds out of the north that create a condition known as upwelling, which kickstarts the ocean food web by stirring the water from bottom to top, the agency said.

“If there is no upwelling, there is no phytoplankton growth, no zooplankton growth, and basically you have no food chain that develops, because it all depends on the upwelling,” Peterson said from Newport.

Along with the upwelling issue -- and likely related to it -- is concern about the acidification of the ocean and its similarly toxic effects on the fish. And what a lot of scientists suspect -- but can't yet prove -- is that all these changes are related to the larger phenomenon of global warming.

So listening to the killer whales as they passed by us that day was a bit like listening to the canaries in the coal mines and realizing that they are in trouble -- not their immediate extinction, but a gradual one. And it's happening because of the kind of stewardship of the world's natural resources -- one marked by wasteful squandering as well as by destruction and pollution -- we humans have practiced for centuries.

We can't go on any longer pretending that we're not choking out entire ecosystems with our carelessness. And we certainly can't pretend that it's just not happening.

If the whales do not survive, that means the food both they and we rely upon -- the bounty of fish and other life from the sea -- is gone. And if they are in trouble, then so are we.

[If you want to learn more about these killer whales, be sure to check out the excellent work of the Orca Network and the Center For Whale Research.]