Where oh Where are the Blues?

A story from Dave Cade, PhD.

Blue whale exhaling

Dave just earned his doctorate working on cetacean foraging ecology, that is, looking in-depth at how whales feed and the world they feed in. Instead of humpback whales, Dave takes us out tagging blue whales, the largest animals to ever have lived on this planet. Getting to know your subjects is key for scientific success.

DAVID CADE is currently a PhD candidate working in the Goldbogen Lab at Stanford’s Hopkins Marine Station in Pacific Grove, California. He’s a cetacean foraging ecologist who looks at interactions of blue whales, humpbacks, and other rorqual whales with their prey. David studies how different foraging conditions affect the dynamics of rorqual feeding.

David was born on the East Coast outside of Washington, DC, but moved to Portland, Oregon when his father got transferred for work. David did most of his growing up in Portland, then moved to the San Francisco Bay area in 2004, where he finished high school and did his university undergraduate work.

He had come down to the Monterey Bay to go whale watching when he lived in San Francisco, and like a lot of people began to fall in love with the area. He recalls coming down one stormy day, and instead of going whale watching going to the Monterey Bay Aquarium instead. He notes it is as great an intro to marine life as you can get. That day, they had a great white shark on exhibit in the open ocean tank, and David was excited that he could watch all the animals interact.

David’s love for Monterey Bay was also nourished by his experiences as a recreational diver. In his words, “The first time you see a cormorant diving through water, you’re like what is going on? The underwater environment is so crazy! Or the first time you see a marine mammal in the water.” One day while diving, David saw sea lions, a harbor seal and a sea otter looking for little invertebrates. He said that was pretty great! He’s always thought that Monterey was one of the best places to dive and see and experience wild life in the world.

While David came into his marine science work from a tangent based on his particular technical skill set, he’s always had an interest in the marine world. David was working on his Masters at Oregon State doing active acoustic work looking at prey field concentrations. He was looking for a PhD opportunity and Jeremy Goldbogen was looking for someone to help him study the prey side of cetacean dynamics. David had been a math engineer for a long time, so has a very quantitative background. This enabled him to start studying the quantitative side of the prey capture work in the Goldbogen Lab.

David now lives in the Monterey area while he pursues his doctorate doing what he loves in a place that he loves.

You can watch Dave’s story on Youtube here: https://youtu.be/HlipmFMO6SQ

WHERE OH WHERE ARE THE BLUES?

I have two stories I want to tell. The first one is my first time diving in Monterey Bay. It really was spectacular; the first time I ever saw a sea otter in the water. I took some students - I used to be a high school teacher. And I took my students down to go diving off the breakwater, and we saw sea otters foraging down there, and diving birds going into the water. It really blew my students’ minds. It’s one of those things you can do to help generate interest in the environment, the ocean environment.

Well, now I study blue whales and humpback whales foraging in Monterey Bay and elsewhere in the world. The first time I ever started tagging blue whales in Monterey Bay was the summer of 2016. In July that year, there were a lot of blue whales up off the north shelf of the canyon, and we went out one day, and that was the year of the fires, the really big fires off Big Sur. And so there was smoke that was kind of like drifting over Monterey Bay, and what it did, it made all the particulates in the air really condense, so there was a lot of fog out on the water.

We were out there trying to work with blue whales on this really foggy, but really calm, calm day. In order to find these whales we would turn off the engines, and we’d listen for the blows. You could hear them, and we’re, “OK, we’re driving down there,” and we’d try to get there to put a tag[1] on an animal. You’ve got to get pretty close, and so we’d listen for the blow then drive in that direction.  Then you’d be fifteen seconds later, and you’d stop again, and you’d listen for the next one, and we just kept doing that and kept doing that. And finally you’d see the whale come up in front of you, and we’d pull up there and put a tag on this animal.

And it turned out to be a pretty cool data set of this whale foraging in really dense, patchy prey conditions. That was a pretty cool experience.

The other story I’d like to share is that this summer we were down in southern California to try to work with blue whales off the Channel Islands. But the wind out there was really, was really rough. So at some point after a few days of working down there, we called it. We said, “We aren’t going to work in southern California. Let’s go up to Monterey Bay, where we know the weather is better.” We’d heard some reports of blue whales, but we were not quite sure what was going on up there.

So we went up to Monterey Bay. We moved all of our operations up there. It was like fifteen people, fifteen scientists all moved up here, and we went out on the water. The first time we went out just with the small boats on a Sunday, and we went out to see what we could find. And we found a few blue whales out along the mid-canyon/ north-canyon edge.

We found a couple animals in pairs, so we put a couple tags out, but we didn’t see a lot of animals. We just put a couple tags out. We were trying to get drone images of these animals, too, so we could measure their sizes in relation to how they forage.

We didn’t get images that day, but we put the tags on. So the next day, we go out to recover the tags, and we’re also looking for more animals so we can do the work and actually get the drone images.

We found a tag floating (need footnote on how they find tags). And what was great was by that time, when we found the tag, the tag had just come off about an hour before we were out there. So while we were looking for the tag, the tag basically lead us to this aggregation of probably 25 blue whales that were out there.

Apparently the animals were foraging in the same place, all night long basically, and we found this great aggregation of animals, and now we knew where they were. And we’re trying to radio – we’re in a separate boat – we’re radioing to our other boat out there that’s tagging a smaller group, “You guys gotta get over here. This is the place to be. Blue whales popping up left and right. If you want to do drone flights of these animals, you can get pictures of the tag on the animal. We can do that over here.”

But they’re out there working with other animals, and they’re trying to do their thing.

Well, we put one tag on, then we’re waiting to bring the big boat over to do the drone flight, so we can get a size estimate of these animals. And we’re just following this animal and trying to keep track of it. While we’re doing that, we got to really know these animals’ patterns. If you’re out there long enough, you start to see the patterns.

We’re out there for probably two hours before the other folks come back, and we get a sense, of like ok: so when they surface, they’re doing these u-shape patterns and going back to the same spot. But when they are surfacing, they often come up say twenty, twelve minutes later at this same distance away in the same direction. So we’re following them, following them, following them.

By the time the other boat gets out there with the photogrammetry equipment so we can measure the size of these animals, we’re like, “OK, guys, here’s what you’ve got to do. Nine minutes exactly from when this animal goes down, you’ve got to go one hundred meters this direction, and then in nine minutes you’ve gotta launch that drone, and the whale will come up right next to you.”

We’re doing our best, and with animals you can never predict that, but sure enough these animals came up right underneath the drone that they had in the air. And we got these beautiful images of the tag on the animal. And because these animals were in pairs, now we have images of two animals, two really nice, clear measurements of these animals.

So now we have a measurement of this second animal, but it doesn’t have a tag on it. Since we want to make sure we can maximize our data use, then we had to do this tagging thing one more time.

We had to predict again where these animals were going to come up so we could tag the other animal in this pair of blue whales, so we could have data on both of these animals. And it worked out really well. It was just a very exciting day to get the data you were looking for and try to understand these animals really well.

Blue whale blows on the horizon

[1] These are suction tags known as D-tags which carry various instruments and are designed to fall off anywhere from 4-24 hours. They are placed on the back of the whale using a long pole. After they fall off, they can be retrieved by the scientists and the data downloaded.