Changes in the world's oceans due to human activities may have devastating effects on many marine species, but a new study said Monday these changes so far have been good for cephalopods, the group including octopuses, cuttlefish and squid.

The study, reported in the U.S. journal Current Biology, showed that cephalopods' numbers have increased significantly over the last six decades.

"The consistency was the biggest surprise," Zoe Doubleday of Australia's University of Adelaide, said in a statement.

"Cephalopods are notoriously variable, and population abundance can fluctuate wildly, both within and among species. The fact that we observed consistent, long-term increases in three diverse groups of cephalopods, which inhabit everything from rock pools to open oceans, is remarkable."

According to the researchers, there has been growing speculation that cephalopod populations were proliferating in response to a changing environment, based partly on trends in cephalopod fisheries.

Cephalopods are known for rapid growth, short lifespans, and extra-sensitive physiologies, which may allow them to adapt more quickly than many other marine species.

To investigate long-term trends in cephalopod abundance, Doubleday and her colleagues assembled global time series of cephalopod catch rates from 1953 to 2013, which inlcuded 35 cephalopod species or genera representing six families.

The data showed that cephalopods, of many different types living all over the world, are on the rise.

The ecological and socio-economic ramifications associated with this increase in cephalopods are much less clear and are likely to be complex, according to the researchers.

"Cephalopods are voracious and adaptable predators and increased predation by cephalopods could impact many prey species, including commercially valuable fish and invertebrates," they wrote.

"Conversely, increases in cephalopod populations could benefit marine predators which are reliant on them for food, as well as human communities reliant on them as a fisheries resource."

What may happen to cephalopod populations in the future is difficult to predict, particularly if fishing pressure continues to increase, they added. Enditem

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