Known for its rocky cliffs and untouched beaches, Chile's Isla de Santa Maria is is a sparsely populated spot. But last month, the island's coastline was suddenly littered with the crimson carcasses of over 10,000 dead Humboldt squid.

Scientists in the area are still working to trace the cause of this mass stranding, but one thing we do know is this is not the result of Fukushima radiation.

The large cephalopods (Dosidicus gigas), sometimes called “jumbo squid” or “red devils”, have been documented stranding like this since 2002, nearly a decade before the Fukushima disaster occurred. As in the case of starfish wasting syndrome and many other wildlife anomalies that sent the internet into radiation-related panic spirals, we can cast the Fukushima hypothesis aside.

Instead, a likely explanation is that the squid encountered an offshore warm-water blob that commonly forms in the area during the Southern Hemisphere’s summer months and recent El Niño weather patterns mean it will be sticking around longer than usual. 

While a stranding of this magnitude has never been observed in Chile, it’s typical to see fish and molluscs wash up dead on Santa Maria as the temperature rises.

In 2011, a similar El Niño brought thousands of South American Humboldt squid to central California, where several strandings followed shortly after. The animals were thought to be chasing deep-sea lanternfish (one of their favourite prey items) as their range expanded due to warming waters. 

"The squid are attracted to steep temperature and salinity gradients in the sea where they find their food," explains Dr Cristina Rodríguez-Benito, who used data from the European Space Agency Envisat satellite to investigate the last mass stranding off the coast of Chile, which happened in 2004. 

Humboldt squid spend roughly 95 percent of their lives at extreme depths, but they move higher in the water column to hunt at sunset. In the case of the '04 stranding, the feeding animals simply found themselves trapped between warm-water masses that carried them inland. 

It's also possible that a "red tide", a toxic bloom of algae, is to blame for last month's stranding. Dr William Gilly and his team at Stanford University's Hopkins Marine Station found that several of the largest Humbolt squid strandings have have coincided with Pacific coastal algal blooms.

The algae produce small quantities of domoic acid, a neurotoxin that could be affecting the animals' central nervous systems and causing them to become disoriented. But a red tide wouldn't explain why no other species seem to have been affected. If this was the result of toxicity in the area, we'd expect to see other animals wash up alongside the squid.

Events like this might be unpleasant and worrying to witness, but for Gilly and his team, they offer a unique opportunity to study the life cycle of animals that reside far beyond our reach. Despite the fact that millions of Humboldt squid cruise the world's oceans, we still don't know where they spawn, and their eggs have never been found in the wild.

Technicians from the Chilean National Service for Fisheries and Aquaculture have collected both squid and water samples for analysis. We'll be updating you as the story unfolds, so watch this space! 


Top header image: kqedquest, Flickr