Squids Thriving as Oceans Warm

Squid, octopus and cuttlefish populations have increased over recent decades while numbers of many fish species have declined.

Squid, octopus and cuttlefish are on the rise, finds new research on these animals, which are collectively known as cephalopods.

Nicknamed the "weeds of the sea," these animals have experienced impressive population growth over the past 60 years and at a time when many fish species have been declining in numbers, according to the new study, which is published in the journal Current Biology.

"Our analyses showed that cephalopod abundance has increased since the 1950s, a result that was remarkably consistent across three distinct groups," lead author Zoë Doubleday, a researcher at the University of Adelaide's Environment Institute and School of Biological Sciences, said in a press release.

Giant Squid Photos

"Cephalopods are often called ‘weeds of the sea' as they have a unique set of biological traits, including rapid growth, short lifespans and flexible development," Doubleday continued. "These allow them to adapt to changing environmental conditions (such as temperature) more quickly than many other marine species, which suggests that they may be benefiting from a changing ocean environment."

What sparked the research was an observed decline of a species that's iconic down under: the giant Australian cuttlefish.

Doubleday explained that researchers started to notice fewer of these cuttlefish at the cephalopod's world-renowned breeding ground in South Australia's Spencer Gulf.

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The scientists compiled a global-scale database of cuttlefish, as well as squid and octopus. Not only did the study reveal that the giant Australian cuttlefish is already making a major comeback, but also that most other related animals have been increasing in numbers over the past six decades.

Like weeds taking over a garden, however, the news isn't all good.

Co-author Bronwyn Gillanders said large-scale changes to the marine environment, brought about by human activities, could be driving the global increase in cephalopods.

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"Cephalopods are an ecologically and commercially important group of invertebrates that are highly sensitive to changes in the environment," Gillanders said. "We're currently investigating what may be causing them to proliferate - global warming and overfishing of fish species are two theories. It is a difficult, but important question to answer, as it may tell us an even bigger story about how human activities are changing the ocean."

Cephalopods are found in all marine habitats and are voracious predators. On the flip side, they are an important source of food for many marine species, as well as people.

This means, Doubleday says, "the increase in abundance has significant and complex implications for both the marine food web and us."

A bobtail squid, shown, is among the cephalopods whose numbers are growing.

What has eight arms with hundreds of suckers, eyes the size of grapefruit and a razor-sharp beak? A giant squid! A team of scientists and the Discovery Channel shot footage of this notoriously elusive creature in action. Click ahead for more squidly fun.

Giant squid have captured, and terrified, the seafaring imagination for centuries. This illustration recreates a giant squid observed off Tenerife in November of 1861.

This giant squid was collected by NOAA researchers off the Louisiana coast in the Gulf of Mexico. The largest invertebrate on Earth, the giant squid is just plain big -- the largest ever found was 59 feet (18 meters) long.

The only squid bigger than a giant is the colossal squid. Captain John Bennett examines the world's first intact adult male colossal squid in 2007 in the Ross Sea, near Antarctica. The squid was about 33 feet (10 meters) long. Check out those suckers!

These two female giant squid were found off Luarca, Spain. For an idea of the size of these creatures, note the gloved hand in the upper-left.

Alien autopsy? Nope. It's one of the Luarca squid from the previous slide, undergoing an examination by Spanish scientists.

Here's a giant squid measuring about 28 feet (9 meters), on display at London's Natural History Museum. This creature was caught in March of 2004, at a depth of 722 feet (220 meters), off the Falkland Islands in the South Atlantic.

A cat strolls past a giant squid in January 2005 in Newport Beach, Calif. That winter hundreds of 3- to 4-foot-long (0.9 to 1.2 meter) squid washed up along the Southern California coast. One theory holds that they ran ashore while chasing grunion.

This is another shot of a squid from the Newport Beach, Calif. wash-up. Giant squid eyes look so human because they’re structured much like human eyes are.

It may look big in the photo, but this larval squid is just 0.4 inches (1 centimeter) long and was photographed through a microscope by Russ Hopcroft, of the University of Alaska Fairbanks.

The humboldt, or jumbo, squid is a carnivorous marine invertebrate with a lifespan of only 1-2 years. But it makes hay while the sun shines on its short life: In that time, it can grow to 4 feet (1.2 meters) long.

We may know it better as calamari, the familiar appetizer, but its proper name is common market squid. This adult market squid was photographed off La Jolla Shores Beach in La Jolla, Calif.

This adult jumbo squid was caught near the Channel Islands by a squid jig aboard an NOAA research ship in 2007. Its tentacles are wrapped around the jig that was used to catch it, which worked by attracting the squid to its glowing yellow plastic.

This is a closer look at the 2007 Channel Islands squid. Its telltale large eyes allow the creature to see in the very low light that permeates its deep underwater habitat.

A squid's razor-sharp beak is a merciless weapon against its prey, allowing it to chomp tasty bites out of its victims. Here we see a close-up of a Caribbean reef squid's beak.

Giant squid aren't without enemies. They're a preferred meal for sperm whales. The whale usually wins, but the giant squid doesn't go down without a fight. Scientists know this because of squid sucker markings, like these, found on dead whale skin.