However, no one has tested the effects of lower levels of the chemical on squid.
But new evidence points to the red tide as at least one cause of the mass strandings. While most sea life follows daily tidal or lunar cycles, the mass deaths seem to be happening every three weeks. That led one of Gilly's graduate students, R. Russell Williams, to see if something in the environment was leading them astray.
"He was fixated in finding some kind of environmental signal," Gilly said.
Russell found that red tides occurred every three weeks, around the same time as the squid strandings, suggesting a link, Gilly said.
While past researchers have only found trace levels of the toxic red-tide chemical in stranded squid, low doses of domoic could essentially be making the squid drunk. Combined with navigating unfamiliar waters, that could cause the mass die-offs.
"They could be tipped over the edge by something like domoic acid that might cloud their judgment," Gilly said.
This isn't the first time Gilly and his colleagues have been led on a CSI-like hunt for Humboldt squid. In 2011, they figured out why the elusive jumbo squid left their usual feeding grounds off the Baja California coast in the winter of 2009 to 2010. Apparently, the squid had moved north, following their prey, small, bioluminescent fish called lantern fish, which had also moved north due to El Niño weather patterns.
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