Jane Stevens at Hopkins Marine Station, Pacific Grove, CA -- Will giant Humboldt squid take over Northern California's fisheries? It's a question that the producers at KQED-TV's QUEST asked squid researcher Bill Gilly in a terrific segment that will air tomorrow, Tuesday, April 1.
Humboldt squid live for two years, grow to six feet and can weigh up to 100 pounds. They swim in schools and feed voraciously on other squid species, anchovies, sardines, hake and rockfish, all important fisheries off the coast of Northern California. Millions have extended their range north from their traditional southern warm waters in a big way, and may threaten existing fisheries.
A Humboldt squid, a frame grab from "The Fierce Humboldt Squid" on KQED-TV's QUEST.
You can check out the story now -- it's on their site, in a larger view. And if you want to see it on your larger TV screen, check KQED's airdate schedule.
And we've embedded it here, in the small view. It's about 10 minutes long, and well worth watching.
The QUEST story touches briefly on one reason why millions of these giant squid have expanded their range (they haven't moved....they're still in great numbers off the Pacific coasts of Central and South America). It's the OML -- the oxygen minimum layer -- that may be growing. The OML -- a rich layer of water about a quarter of a mile thick whose top is 1500 feet (300 meters) below the ocean surface -- is a favorite hangout for squid. Gazillions of tasty (to squid) lanternfish (pictured here at about actual size), shrimp-like krill, and tiny squid species live here. It's called the OML because this is where bacteria use up nearly all the oxygen in the water as they metabolize, or break down, detritis that rains from the surface, where the tiniest animals eat the ocean's tiniest plants and help create all that detritis.
Gilly's been putting satellite tags on squid for a few years. The tags record what they're doing every one or two seconds for a month, then release, float to the surface and transmit data via satellite to Gilly's computers. The interesting thing that he's discovered is that these humongous, fast-moving (25 mph) animals, who you'd think would need lots of oxygen to zip around, thrive in the OML. The animals that eat squid -- yellowfin tuna, bluefin tuna, swordfish -- can only zip in and out. Only the large elephant seals, who can hold their breath for 20 to 40 minutes as they dive deep, can follow squid into the OML.
In the worlds' largest migration, the animals that live in the OML swim to the surface every night to feed on the phytoplankton. As Gilly noted in a paper about the OML, "the OML is a vast midwater region that is a crucial part of the some of the world’s most productive pelagic ecosystems. It results from high primary productivity at the surface and provides a powerful trophic link back to many top predators...It most certainly should not be thought of as a ‘deadzone,’a term often applied to some near-shore hypoxic zones such as a large region in the Gulf of Mexico associated with Mississippi River discharge." The OML at the left depicts a cross-section of the Sea of Cortez, where Gilly has been tagging squid and finding an interesting development.
There wasn't much of a squid fishery in the Sea of Cortez before the 1960s, and now it's a 100,000-ton fishery. Squid began showing up in increasing numbers in the Sea of Cortez when large-scale wheat farming began dumping tons of nitrogen fertilizers into the Guaymas Basin. This nitrogen is feeding the OML. There's natural upwelling of phytoplankton from the cold waters beneath the OML in summer, but the nitrogen seems to be contributing to phytoplankton blooms, which feed the OML in winter. Gilly thinks that "agricultural practices in the Yaqui Valley have changed the ecological balance in the Sea of Cortez by chronic enhancement of physical and biological features of the OML in a way that favors squid."
This is an image of the OML in the Pacific. OMLs are good. They're an "integral part of a highly productive marine ecosystem," says Gilly, because the small fish and crustaceans that live in the top part of the OML during the day migrate to the surface at night and feed a plethora of animals -- tuna, sharks, whales, humans. In the KQED-TV story, Gilly says that the OML may be growing -- getting thicker and coming closer to the surface. And where the OML grows, the squid follow.
Nobody knows why the OML is growing, though. Does it have something to do with climate change? Is it related to agriculture? It would be handy to know.
A Humboldt squid jetting away in a frame grab from "The Fierce Humboldt Squid" on KQED-TV's QUEST.