MercoPress. South Atlantic News Agency

Humboldt squid spawn earlier and migrate for food under influence from El Niño

Professor William Gilly is assisted by Huli Cat deckhand Gary Christensen as he affixes a GPS satellite tag to a newly caught Humboldt squid (Photo:Sheraz Sadiq)

Stanford University marine biologist William Gilly and other researchers have been studying Humboldt squid in Mexico's Sea of Cortez to determine why the animals have been spawning at a much younger age and smaller size than usual.

They believe El Niño is the cause and Gilly is in the second year of studying how exactly the El Niño weather pattern during the winter of 2009-10 affected squid.

In May 2010, Gilly and a biology class of Stanford undergraduates discovered that the typically abundant squid were largely gone.

“There were far fewer of them than normal, they were spread out over a huge area and they were very small. But they were also sexually mature and spawning, at a ridiculously small size” Gilly said.

“It was obvious that the squid were pretty screwed up,” he remarked.

While normally Humboldt squid (Dosidicus gigas) spawn when they are 12-18 months old, Gilly found spawning squids of less than 6 months and weighing 1 lb each, compared with the usual 20-30 lb at maturity.

Gilly and students eventually found large squid about 100 mi farther north than normal, near the Midriff Islands, where Gilly surmises they had ventured in search of food.

Squids' usual coastal habitat off Baja California provides them with copious phytoplankton and thereby food consisting of marine animals of all types, thanks to up-welling which stirs cold nutrient-rich waters up from the deep.

But El Niño brings warm nutrient-poor tropical water by forcing cooler water down 150 ft or more below the surface, which is then too weak to haul the cool, nutritious water back up. As a result, the phytoplankton population and all the creatures it nourishes disappear. This may be why the squid swam farther in search of better food stocks.

“Squid can move to an area of tidal up-welling, which remains productive during an El Niño condition, and continue on their merry, giant-squid lifestyle and live to spawn when they are a year and a half old,” Gilly said.

Squid may also move into an open-ocean environment where food is less plentiful but the supply is steady. “It is comparatively meagre fare and it will not get to be a big giant squid, so instead it reproduces when it is 6 in-long,” he said.

Although oceanographic conditions returned to normal this year, Gilly again found big squid only around the Midriff Islands. The small squid were larger than the year prior by about 25-30%, and they were beginning to repopulate their old grounds.

Gilly suspects that each new generation of squid may lead them to rediscover the rich lantern fish feeding grounds of their ancestors and the average squid will grow a little larger.

Whether the descendants of the squid that moved north will remain around the Midriff Islands and spawn a new and stable squid fishery remains unknown. The food brought up by the tidal up-welling is mostly krill -- much smaller and probably less nutritious than the usual lantern fish -- so it takes a lot more krill to help a Humboldt squid reach its full physical potential.

A revival of the lantern fish may eventually attract most of the squid back down south and reunite the whole squid Diaspora. (FIS/MP).-