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News  Envisat fishes up facts behind Chilean giant squid invasion
Masses of large ocean-going squid have inundated the shores of Southern Chile, alarming local fishermen who fear these carnivorous invaders could threaten fish stocks. Envisat has helped account for their otherwise mysterious arrival. These jumbo flying squid – Dosidicus gigas is their Latin name – are some of the largest known squids on the planet: the ones here measure between 70 to 150 centimetres in length, although specimens have been known to reach more than three metres. Making their home in the open ocean, they rise to the surface at night to aggressively feed on small fish using barbed suckers.
In the final days of February more than 200 of the squid were washed up on the beaches around Ancud, on the northern coast of the island of Chiloé in southern Chile. Further incursions have since taken place towards Calbuco, on the inner side of the Chacao channel and towards the southern part of the island along the coast, up to Castro in the middle of the big island of 'Los Lagos' region of the country. Strandings have also been reported in more northerly areas such as Chile's VIII region.
But an explanation for the incursions was available – from 800 km away in space. Envisat's Advanced Along Track Scanning Radiometer (AATSR) instrument works like a space-based thermometer, taking the temperature of land and sea as it orbits the Earth. It can measure sea surface temperature (SST) to an accuracy of 0.3 degrees centigrade at a spatial resolution of one square km.
"The AATSR results show the appearance of the squid was connected with changes in the water mass conditions off the coast of Southern Chile in recent weeks," says Dr Cristina Rodríguez-Benito of oceanography company Mariscope Chilena.
"This caused an influx of warmer water, between 0.5 and 1.5 degrees, and also squid, which are attracted to steep temperature and salinity gradients in the sea where they find their food," adds Rodríguez-Benito. "The squid ended up in a lens of cold water between warmer masses, and this carried them into the inner Gulf of Ancud area.
"Even more important than temperature is the indication of the entrance of a water mass poor in oxygen that could be the reason for the losses already registered in some aquaculture sites.
The team plans to present their experiences of using Envisat data in this way to a conference this month of the Chilean Civil Protection Organisation.
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