Humboldt squid thriving, thanks to ocean dead zones

Human-size jumbo squid are growing thick along the U.S. west coast. Is climate change aiding their expansion?

By Katherine Harmon   
April 8, 2010 Although many of the Pacific Ocean’s big species are floundering, one large creature of the deep seems to be flourishing. The Humboldt squid (Dosidicus gigas, also known as jumbo squid, owing to its sizable nature) has been steadily expanding its population and range: whereas sightings north of San Diego were rare 10 years ago, the squid are now found as far north as Alaska.

Many researchers attribute the squid’s recent success to the very climate, current and oxygen-level changes that have been hurting populations of other species in the diverse California Current. “I find their adaptability and their perfection in dealing with anything nature throws at them to be a remarkable feature,” says William Gilly, a professor of biology at Stanford University whose lab has spearheaded much of the U.S. work on Humboldt squid. “They’re able to explore and take advantage of new environments that are compromised in any way.” And they can move quickly, says John Field, a fisheries biologist with the National Oceanic and Atmospheric Administration’s Southwest Fisheries Center, adding: “They’re capable of very large migration patterns.” Gilly’s group recorded one squid that was tagged in Monterey, Calif., and last detected around Mexico 17 days later. … As evidence for their impact on U.S. fisheries continues to trickle in, their effect off in Chile, where the squid have been prevalent for much longer than most parts off the U.S. coast, has been more conspicuous: “There’s very strong evidence that the squid expansion had a huge impact on the hake fisheries,” says Field, who helped organize a symposium on the animal in 2007. “It looks like they’re doing the same migration as hake, which concerns me.” … One factor contributing to the squids’ expansion seems to be the eastern Pacific’s growing dead zones, where they spend much of the day. Well-known river-mouth hypoxic zones, such as the dead zone in the Gulf of Mexico, are fed by agricultural runoff and the algal blooms it encourages. But deep-sea low-oxygen zones are naturally occurring, integral parts of larger oceanic systems, where organic matter filters down from highly productive areas only to be consumed by anaerobic bacteria that emit carbon dioxide. In such environments, dissolved oxygen levels are so low that many ocean creatures, such as large predatory fish, have trouble staying for long. Changes in climate, water stratification, wind patterns and currents in the Pacific might all be playing a role in expanding these hypoxic zones, Gilly explains. Despite their dreary name, these growing dead zones are likely boosting Humboldt squid numbers. In warmer water areas these low-oxygen zones often start 200 meters below the surface and extend in the water column down to about 1,000 meters. Off the coast of California, however, Gilly explains, these zones have historically started at a depth closer to 400 or 500 meters, making them much smaller. But in recent years, “that zone is getting bigger” and low oxygen areas have been growing closer to the surface off the coast of North America. Off Oregon, for example, many of the past summers have brought a new seasonal dead zone close to the coast. This change has meant less livable ocean habitat for many creatures that depend on well-oxygenated water to survive. But for Humboldt squid the expansion of these dead zones has been a lifeline to new habitats. Gilly and his lab have discovered the squid can hang out hundreds of meters down in areas that hold as little as 10 percent of standard surface oxygen levels for a whole day. In fact, the squid do not just seem to tolerate these harsh aqueous climes, but they appear to actually “have an affinity for and favor” them, Gilly notes. Just why Humboldt squid are thriving deep in these low-oxygen zones remains a mystery. …

Humboldt Squid Seem to Be Thriving–Thanks to Ocean Dead Zones