"Guess what we found!" My excited bunkmate woke me from a nap. I was exhausted from babysitting squid embryos all night, and she was wet from blue-water diving in the Gulf of California. I could guess. "An egg mass!" I scrambled out of bed to follow her to the ship's lab, where the rest of the divers proudly presented me with three glass jars full of transparent gelatinous goo and squid eggs the size of rice grains.
|Embryos in a Humboldt squid egg mass.|
Credit: Steven Haddock
It was the high point of my doctoral research. And it was the blindest luck. The divers weren't expecting to see a Humboldt squid egg mass sixteen meters below the surface on that warm June day in 2006. They'd been looking for jellyfish when they noticed the car-sized blob, studded with at least half a million eggs. (That may sound like it would be easy to find, but it's a mere smudge in the gargantuan vastness of the open ocean. And a fleeting smudge at that--it may last no more than a week.)
Of the many squid scientists on board the R/V New Horizon, the egg-filled jars came to me because I was the one obsessed with baby squid. Up until then, I'd been generating all my babies in vitro. A Petri dish on a lab bench is quite a different environment from a big blob in the sea, so I was pleased to find that the egg-mass babies agreed with my artificially fertilized babies about some important things, like temperature.
The water in the Gulf at the depth of the egg mass was warm, about 25°C. I kept the jars at around that temperature, and within hours the eggs began to turn into adorable little specks that squidged through the water, while the jelly disintegrated and sank. Artificially fertilized eggs also thrive at 25°C, developing healthy eyes, arms, ink sac, and so forth, and hatching in less than a week. Based on these and further studies, and maps of ocean temperature, I guessed that Humboldt squid have two main spawning grounds: off the coast of Mexico and off the coast of Peru.
|Author with Petri dishes at microscope.|
Credit: Ashley Booth
Adults may travel to these spawning grounds from the broader range of the species. Humboldt squid live throughout the eastern Pacific, from Mexico to Chile, with periodic expansions further north and south. In the last decade, Humboldt squid have become regular visitors to California, with occasional appearances as far north as Alaska. However, my in vitro experiments imply that these polar explorers must return all the way to Mexico to have their babies. Egg development slows as the temperature drops, and arrests completely below 15°C.
But that’s just where it starts to get cozy for the babies of another species: the market squid, whose embryos prefer 9-13°C water. California is their perfect nursery. In these cooler waters, market squid eggs take much longer to develop than Humboldt squid eggs—weeks rather than days—and when they do hatch, baby market squid are twice the size of baby Humboldts (although twice the size of a grain of rice is not exactly large).
Curiously, these relationships are reversed in the adults. Grown Humboldt squid are famous for their size, reaching over a meter in mantle length (the length of the main body, excluding head and arms) and dwarfing the typical 10-15 centimeters of market squid mantles. Then, despite their speedy development in the egg, Humboldt squid can live up to two years--a respectable age for a squid. Market squid tap out at 6-9 months.
The two species' reproductive habits are wildly different as well. Scientists may have seen Humboldt squid mating once. We're not sure. We've never seen them lay their tremendous egg masses--and we haven't seen another mass since 2006. On the other hand, most recreational divers in California have seen or at least heard of the spawning grounds where market squid gather by the millions to mate, lay their eggs, and die. Females package one or two hundred eggs into a finger-sized capsule, which they glue to the sand, or a rock, or a weed . . . again and again, until the seafloor is strewn with "mops" of eggs.
A concurrent aggregation of fishing boats takes place overhead, using bright lights and big nets to collect the conveniently assembled squid. At my home lab in Monterey, we would wander out from our offices and count the boats during squid season, keeping a running tally on the whiteboard. Sometimes when we needed some squid for a research project, we would grab a cooler and a small net, fire up the motor of our little Boston Whaler and putt out to visit. "Hello there, we're scientists, we sure do admire how hard you're working, and could we please take a small scoop from your magnificent net?" (It may have been phrased differently; I don't remember the details.) The fishermen were generous and obliging, and that night we would have market squid swimming in our tanks, the females periodically affixing egg capsules to the fake ones a postdoc had made.
|Author jigging for Humboldt squid.|
Credit: Ashley Booth
Humboldt squid make no such net-friendly gatherings, and must be caught one at the time with a jig and a line. Humans are pretty capable with a jig and a line, though: in 2011, almost a million tons of Humboldt squid were landed, making it the largest invertebrate fishery in the world. Market squid aren't too far behind; they support California's largest fishery of any kind.
Though both Humboldt and market squid live in the eastern Pacific, many are shipped west after being fished. But some stay home, and you may well have eaten them. The mantles of the smaller market squid are cleaned out to make tubes, which are then sliced into the familiar forms of calamari rings. To do the same with a Humboldt squid would make girdles rather than rings; instead, they are prepared as squid steaks.
Popular as they are with human diners, squid are arguably even more popular with other marine predators. Fish, sharks, seals, whales--all are eager to chow down on these swimming protein bars. And squid are equally happy to eat each other. Humboldt squid being so much larger than market squid, it's obvious who would be eating whom. In the past, the ranges of the two species haven’t overlapped much, perhaps partly because their babies prefer to develop at different temperatures. But as Humboldt squid move north, could they threaten California’s biggest fishery?
The answer depends on how the two species respond to a changing ocean. At first, it might seem that Humboldt squid are the clear winners. The ocean is warming, and their eggs prefer warmer temperatures. Meanwhile, their range expansion is thought to be tied to the expansion of low-oxygen zones, a normal part of the deep ocean that has been stable for a long time. Now these zones seem to be growing in all directions, spreading out and getting shallower. Although most large animals can’t stand the low oxygen, Humboldt squid are specially adapted to take advantage of it.
But environmental changes have complex repercussions, and the results aren't so clear as "winners" and "losers." The recent 2009-2010 El Niño caused the Humboldt squid fishery in Mexico to crash spectacularly. The animals may have adapted to their altered habitat by maturing at smaller sizes and moving further out to sea, and as conditions return to normal, Humboldt squid may as well. Market squid also respond strongly to El Niño, which has historically caused declines in the fishery catch. Yet in 2010, fishermen caught so many market squid that they reached the management quota of 118,000 metric tons for the first time. It happened again in 2011 and 2012. The simplest explanation: it's complicated.
|Baby Humboldt squid.|
Credit: Danna Staaf
Squid are more resilient and responsive than many other animals, thanks to their quick generations, abundant babies, and the ability to migrate. These “weedy” traits might be enough to let squid—or at least some squid—survive climate change, even thrive with it. They also lead some people to consider squid fisheries the ultimate in sustainability, but other people are concerned that squids' quick responses to environmental change could actually make them more vulnerable.
Squids' importance as a food item for so many marine animals and, yes, humans, is enough reason to hope they stick around. But there are other reasons, too: beauty, wonder, mystery. Consider the vast market squid egg beds, piles and heaps and mountains of gently swaying mops, shining white in the green murk (worth braving 9°C water), and the sudden appearance in blue water of a dim gelatinous mass large enough to swim through, filled with eggs so tiny you can barely see the Humboldt squid pulsing inside (worth getting out of bed).