In the squids' usual coastal habitat off Baja California, upwelling brings cold nutrient-rich water up from the deep, causing phytoplankton to bloom and marine animals of all types to congregate. The squids' palates are particularly partial to lantern fish a slender, silvery, pinky-finger-sized species named for the small light-emitting organs on its sides.
But during an El Nio, warm nutrient-poor tropical water from the open ocean flows into the Sea of Cortez and pushes cooler water down 150 feet or more below the surface. The usual upwelling, driven by the wind, is not strong enough to pull the cool, nutritious water back up. So the upwelling just recycles the warmer water, causing the phytoplankton population and all the creatures that depend on it to crash.
That crash likely sent the squid searching for better food stocks, which could have led them to the Midriff Islands, where upwelling is driven by strong tides unaffected by El Nio.
"Squid can move to an area of tidal upwelling, which remains productive during an El Nio, and continue on their merry, giant-squid lifestyle and live to spawn when they are a year and a half old," Gilly said. Or they can move away from land into an open-ocean environment, where food is less abundant but the supply is steady, as its availability doesn't depend on upwelling.
"It is comparatively meager fare and you will not get to be a big giant squid, so instead you reproduce when you are six inches long. It is a different strategy, but it works," he said.
With oceanographic conditions back to normal this year, when Gilly headed down to Baja again, he expected that the squid situation would probably be normal, too. But big squid were again only found around the Midriff Islands.
While small squid were present throughout the Sea of Cortez, the little ones were larger than the year before by about 25 to 30 percent. And they were beginning to repopulate their old feeding grou
|Contact: Louis Bergeron|