by Edith Widder
The richness of life in these surface waters is what makes this fishery so productive. Like the Gulf Stream and the Kuroshio Current, the Humboldt Current, from which the ravenous squid gets its name, is a major part of the ocean’s circulation pattern, flowing north along the west coast of South America. The current creates upwellings of nutrients, which are the building blocks of life and the foundation for the exceptional biomass found here.
I knew this in theory, but seeing it in practice was still a surprise. The water was a dark teal green at the surface, rich with phytoplankton, and at 150 feet it was jelly soup—a gumbo of gelatinous life-forms feeding off the phytoplankton and one another. But as we descended farther, that profusion of life began to thin out. By 700 feet, any signs of macroscopic life disappeared and the water turned milky. This was the center of the oxygen minimum zone (OMZ)—the yin to the surface layer’s yang.
Everything that lives must eventually die. As the phytoplankton and zooplankton at the surface expire and sink toward the bottom, they are consumed and decomposed by microbes. This process uses up large quantities of oxygen. In some regions, usually along the western coasts of continents, a lack of mixing can lead to a distinct layer of water with insufficient oxygen concentrations for most of the ocean’s larger life-forms, a wet desert that fluctuates in size, depth, and range.
We were far below sunlight’s reach, just coming out of the bottom of the oxygen minimum zone at about 1,090 feet, when we saw that first Humboldt. As we continued downward, we passed through a scattering of lanternfish, a common prey item for Humboldt squid. Lanternfish, so named because their bodies are studded with light organs, are found anywhere the water is deep and salty, which is more or less most of the world’s oceans. Here they seemed to be concentrated in a layer between 1,800 and 2,100 feet. As we sank through this layer, we saw seven more Humboldts, with the last two at around 2,070 feet, one of which attacked the e-jelly. After that, the animal life thinned out until we approached the bottom, at 2,990 feet.
It had taken us more than an hour to journey a distance of less than twelve city blocks, but we had gone through the looking glass to another world. Here we found an abundance of a very different kind of life, in the form of the largest number I’d ever seen of a creature first described by ROV pilots as “headless chicken fish.” In fact, they’re Enypniastes, a type of pelagic sea cucumber, and I actually think they’re beautiful. Granted, if you squint, the animal’s body does bear a striking resemblance to a headless, wingless plucked chicken, but it swims by means of a large, webbed veil at its front end that pulls it through the water with balletic grace. The veil first points forward and then spreads out like a fan and curls backward, pushing water out between the veil and its body.
Their color is also very un-chickenlike. They are semitransparent, with a pinkish or reddish hue when seen under white light. Even more fantastic is the sticky blue bioluminescent fairy dust that rubs off their bodies upon contact, which serves as a defense against predators in the same way that exploding paint packets thwart bank robbers. Any predator foolish enough to try to chow down on one of these “chicken fish” would find itself with the equivalent of a glowing bull’s-eye painted on it, making it an easy target for its predators.
I had often seen Enypniastes as solitary swimmers or in small groupings of two or three at a time, but here there were hundreds. It looked like a hot-air balloon festival, all these chicken fish drifting or swimming at different heights while others grazed on the bottom, rolling out lacy-edged feeding tentacles that gathered sediment into their mouths. They are the vacuum cleaners of the seafloor, and their abundance made perfect sense, given the dense rain of detritus from above.
I wanted to stay and enjoy the ballet, but we had gotten the disappointing word from mission control that the weather was picking up and we were being called back to the surface early. It was now approaching sunset, and as we ascended, we found that the lanternfish had started to migrate up. Clearly, in these inky dark waters, their diurnal journey wasn’t triggered by light, so I wondered if their internal clocks were providing the migration cue. From the fish’s minimum depth of 1,800 feet on our descent, they now extended up to 1,000 feet, and it was in their upper range, between 1,000 and 1,300 feet, just below the OMZ, that we again found the Humboldt squid. They were now hunting in earnest.
It was a different kind of attack from the one we had seen earlier on the e-jelly. It started out the same, the squid homing in on the fish, arms held together in a tight point, but then the eight arms splayed apart and two elastic tentacles shot out, grabbing the fish, which flashed a bioluminescent scream for help. At the same time, some of the squid produced a stroboscopic visual effect, changing their entire body color from red to white, shifting back and forth two to four times per second—a hugely intimidating display in such a large, aggressive predator. Intriguingly, it never seemed to happen when we saw just one squid alone. Strobing occurred only when there was more than one Humboldt in sight. This was communication—the transfer of information—and it was about as subtle as a jackhammer. But what were they saying?
When cannibals chow down, it’s pretty important that there be no miscommunication. If two cannibals try to attack the same prey at the same time, the loser might just decide to attack and eat the winner. In squid-on-squid aggression, size differences play a big part in determining who is the diner and who is the dinner. Whole-body strobing is one way to convey intention—I’m about to attack this fish. It’s mine. Stay away!—as well as vital size and strength data: Back off, buddy! I’m bigger than you.
We saw more than thirty squid on that first dive, which for me was nirvana. But for Orla and Hugh, in the Triton, it was frustrating to be close enough to see the squid, yet so far away that we couldn’t get the kinds of shots they needed. Still, at least we knew the squid were here. Hopefully, all we needed to do was be patient and keep trying.
However, with subsequent dives we kept seeing squid, and they were consistently being drawn to the e-jelly, but we weren’t getting the shots Orla needed. The problem was by design, sadly. Because the burglar alarm is a last-ditch scream for help, secondary predators must respond quickly, before the primary predator extinguishes its landing beacon by consuming the prey and departing. This meant that the Humboldts homed in on the e-jelly at high speed and, when they found nothing to eat, zoomed out again just as fast.
In an attempt to get the squid to stay longer, we tried attaching a bait squid next to the e-jelly. This produced what I considered cinematic gold. A hefty seven-foot Humboldt came in on the e-jelly and grabbed on to the bait squid, attempting to wrench it free, while its whole body pulsated back and forth between red and white. The sub shook with the force of the squid’s yanks, and the brute did not give up easily, which meant we got a lot of footage. This seemed ideal to me, but Orla feared she couldn’t use it because it would not be deemed natural behavior by the Blue Planet team.
On another occasion, during one of the few dives when I wasn’t in the sub,*3 they actually managed to film an incidence of cannibalism—the first time this behavior was ever recorded! A large squid grabbed a smaller one and then spewed out a smoke screen of black ink to try to hide its prize, but to no avail, upon which an even larger squid swooped in to grab it and, after a brief tug-of-war, stole it away. This whole scene was filmed in close-up, which was phenomenal but very brief. Much more was needed to tell the story.
And suddenly it was our last dive. We had a long list of things we needed to accomplish. My number-one priority was filming bioluminescence. I had managed to convince Orla that an important part of the Humboldt squid story was figuring out what part bioluminescence plays in its visual communications repertoire. All the body strobing we had been seeing didn’t make any sense if it was occurring in pitch darkness. However, since small photophores cover the Humboldt’s body, including the mantle, head, tentacles, arms, and fins, both top and bottom, it seemed like
ly that the same body strobing could be replicated with bioluminescence but that we weren’t seeing it because our red lights were too bright.
There was one dive where I thought I saw bioluminescence from the squid, but I wasn’t sure. We had been sitting in the dark with all of Deep Rover’s lights turned off, and I was looking down, watching a group of Humboldt squid far below me, just barely visible in the red lights of the Triton. These squid were strobing, but instead of the usual red-and-white whole-body color change, it looked like blue bioluminescence flashing on and off. It was very dim, and, knowing how obliging the human brain can be at filling in details based on what one expects to see, I wanted video confirmation. But Orla had been loath to turn out the lights when squid were present, for fear of missing a shot. If the squid were hanging around enough to be filmed under our red-light illuminators, that was her priority. Going dark on the off chance that they might be emitting bioluminescence seemed too risky a bet.
But this time we were specifically going to try to film the bioluminescence of the squid, as well as of the bioluminescent plankton in the water, which we planned to stimulate with a SPLAT screen we had jury-rigged on the Triton. I was confident that the low-light BBC camera was going to provide spectacular imagery from the plankton—a sure thing. We also planned to spend some time on the bottom filming all those chicken fish, including their bioluminescence—another sure thing.
The plan was to launch at ten a.m. and descend straight to the bottom, stopping to film only if we encountered squid. On the seafloor, we would spend some time filming Enypniastes, then we would start up slowly, recording bioluminescent plankton at 50-meter (164-foot) depth intervals, all the time hoping to come across an aggregation of squid. We had eight hours.
Once again it was me and Toby in the Deep Rover, and Orla and Hugh in the Triton, with Alan Scott as their pilot. It had taken us a little over an hour to reach bottom, and although the goal was to keep the subs close to each other, we had lost sight of the Triton well before we settled down on the seafloor, at three thousand feet. We began to get concerned because Al was not responding to Toby’s attempts to raise him on the through-water comms. Toby tried to pick the Triton up on our sonar display but had no luck. Next he called the surface to see if mission control could make contact. No joy there, either. The team on the ship was, however, able to get a position for the Triton from the USBL (ultrashort baseline) beacon. They could also see it on the echo sounder, showing it to be a few hundred feet off the bottom, which seemed strange.
At least now we had a direction in which to start looking. As we motored toward them, Toby kept trying the comms, and after many tries, we finally got a curt reply from Al saying that he was dealing with an intermittent failure of his computer control system. This was simultaneously a relief and a crushing disappointment—a relief because it was not life-threatening, since he could simply blow ballast and surface the sub without computer control, but disappointing because it meant we might have to abort the dive.
By the time we reached them, Al had managed to regain enough control that he had the sub sitting on the bottom, and as we drew closer I could see Orla in the starboard seat, her legs tucked under her, looking almost relaxed except for the sour expression on her face, in stark contrast to her usual cheery smile. While Al kept fighting with the computer, Toby and I reconnoitered the surrounding area. As we cruised over the bottom, I mused on the irrefutable nature of Murphy’s law: Not only were we facing an equipment meltdown, but the ocean had thrown us another curve. There weren’t any Enypniastes anywhere in sight! Instead of chicken fish, the seafloor was carpeted with large, bottom-dwelling shrimp, each resting in its own shallow indentation in the sediment, golden eyes staring up at us as we soared over them like an invading UFO.
It was apparent that our carefully laid filming plans were kaput. Al had manual override for some of the functions he needed, but trying to film the bioluminescence was proving to be an exercise in frustration. He had control of the thrusters, but he couldn’t turn lights on and off as needed. Nevertheless, both subs remained cruising along the bottom looking for Enypniastes for nearly four hours and eventually found a few, but there was not the magnificent profusion we had seen on previous dives.
With only three hours of our eight-hour dive time left, the two submersibles began to move up through the water column looking for squid. Our expectations weren’t high, because we had seen only one during our descent. But to keep the dive from being a total bust, whenever we saw anything slow-moving, like a jellyfish, that didn’t require a lot of maneuvering by the Triton, we would stop and film it.
It was approaching six p.m. by the time we reached the oxygen minimum zone, and the batteries on both Triton and Deep Rover were nearly drained. We would have to surface soon. The Triton trailed below us, and while waiting for it to catch up, we were surprised by a Humboldt that shot up from below and attacked the underside of the e-jelly. I checked the depth—692 feet. We were smack-dab in the center of the oxygen minimum zone. It’s known that Humboldt squid have a remarkable capacity for surviving very low oxygen by shutting down certain metabolic pathways, but it was assumed that they further reduced oxygen demand when in the OMZ by forgoing active hunting. Well…scratch that hypothesis. This was the very definition of active hunting.
That observation alone would have made the dive worthwhile for me, but the squid weren’t done with their surprises. As we continued to move up, we came into a layer of lanternfish, still within the oxygen minimum zone, and, suddenly, more Humboldts than we had ever seen: hundreds of them, and they were actively hunting the fish. Although we had our white lights on, the squid seemed unperturbed, and, in fact, they were using our lights to see their prey. It was a frenzy of activity, and hard to take it all in. The Triton was below and off to our starboard side, filming the action, so all we had to do was sit still and illuminate the scene for them. And there certainly was no shortage of action. In any direction, they could point their cameras and see squid gliding through the water and hammering at prey.
The squid seemed to spend equal time swimming backward and forward. They would cruise backward, flapping their enormous fins, and then reverse on a dime when they spotted a target. I watched as one after another homed in on its prey, tentacles shooting out, sometimes adjusting their trajectory, even bending their tentacles at the last instant to intercept a fish as it zigged or zagged, sometimes missing, sometimes scoring a direct hit, pulling the fish back to where it disappeared inside a squid’s splay of arms, and sometimes scoring a partial hit that resulted in a spray of shimmering scales. They weren’t infallible hunters, but they were persistent even as the fish were thinning out.
We had been there more than ten minutes, enough time to attract a large swarm of krill, drawn to our lights like moths to a flame. The krill were becoming so thick that they were making it hard to see the squid. Suddenly, a squid swimming directly toward us spread its arms and tentacles wide, forming a kind of basket, and then curled them back toward its mouth, scooping the krill in like popcorn. I had never seen squid feed like that. In fact, I didn’t think anyone had. More squid started coming in then, basket-feeding on the krill.
I wanted to document this, but the Triton was too far away, filming the fishing action at the periphery of our light field. I had my Nikon, but at that precise moment it stopped shooting. I assumed the battery had died and changed it out, without taking my eyes off the show on display in front of the sub. More and more squid were swooping in, shoveling krill into their mouths like contestants in a shrimp-eating contest. When my camera still refused to shoot, I tore my eyes away long enough to realize that the problem wasn’t the battery but a full memory card. As I dug around frantically for a spare, Toby pulled out his iPhone and managed to film thirty seconds, which included four basket-feeding attacks. Tens of thousands of dollars’ worth of camera gear and what should have been the blue-chip natural history moment is shot on an iPhone! Fo
rtunately, I found out later that the same feeding frenzy was happening around the Triton, so they were able to record some of that odd behavior as well.
We had been filming the squid for about fifteen minutes when suddenly they bolted, swimming explosively from left to right across our field of view. It was as if something spooked them—badly. Later, when we were back on the ship and talking to the crew, we learned that at about the time that the squid fled, a Chilean military helicopter had buzzed the ship, followed shortly afterwards by a high-speed military vessel that whizzed past at nearly twenty-four knots.*4 Presumably, the sound had alarmed the squid. Such an extreme flight response sure looked like predator avoidance behavior.
Squid don’t have ears, but they do have statocysts, which allow them to detect low frequencies, below five hundred hertz. Toothed whales would be one sound-producing predator worth avoiding, since they can consume over two thousand pounds of squid each day. However, the only sounds they are known to generate are ultrasonic clicks that they use as a kind of biosonar to locate prey and to communicate. These clicks are composed of frequencies of seventeen thousand hertz, far above the range that squid can detect. In fact, it’s recently been shown that squid are oblivious to and unharmed by ultrasound pulses broadcast at a decibel level that, if in our hearing range, would rupture human eardrums.
So if these squid are insensible to the sounds generated by such obvious predators as toothed whales, what could have elicited such a panic response? Well, another sound-producing predator worth avoiding is humans, since we are equally voracious consumers of squid. Have Humboldt squid learned or evolved to avoid engine noise? Obviously, these animals are highly adaptable. They seem to have a plethora of feeding strategies, shifting prey preference as the situation warrants—from fish to krill to each other. They can tolerate extremely low oxygen levels and, to some degree, may actually be beneficiaries of climate change. Their range in the eastern North Pacific Ocean has recently expanded, and they have invaded waters along the central California coast and been spotted as far north as the Gulf of Alaska. Their extreme adaptability positions them as potential survivors in a rapidly changing world, so it wouldn’t surprise me at all to learn that they have developed a way to detect and avoid motorized fishing fleets.
