As Ocean Temperatures Rise, So Have Squid & Octopus Numbers

The number of cephalopods—octopus, cuttlefish and squid—has increased in the world’s oceans over the past 60 years, possibly due to their ability to adapt to changes in the environment.

AsianScientist (Jun. 1, 2016) – Unlike the declining populations of many fish species, the number of cephalopods—octopus, cuttlefish and squid—has increased in the world’s oceans over the past 60 years, a University of Adelaide study has found.

The international team, led by researchers from the university’s Environment Institute, compiled a global database of cephalopod catch rates to investigate long-term trends in abundance. They published their findings in Current Biology.

“Our analyses showed that cephalopod abundance has increased since the 1950s, a result that was remarkably consistent across three distinct groups,” said lead author Dr. Zoë Doubleday, a research fellow in the Environment Institute and School of Biological Sciences.

“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. 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.”

Doubleday said that the research stemmed from an investigation of declining numbers of the iconic Giant Australian cuttlefish. According to her, there has been a lot of concern over declining numbers of this cuttlefish at the world-renowned breeding ground in South Australia’s Spencer Gulf.

To determine if similar patterns were occurring elsewhere, Doubleday and colleagues compiled this global-scale database. From their data, they found that cephalopods as a whole are in fact increasing. Since the start of this study, cuttlefish numbers from this iconic population near Whyalla in South Australia are bouncing back.

Project leader Professor Bronwyn Gillanders said large-scale changes to the marine environment, brought about by human activities, may be driving the global increase in cephalopods.

“We’re currently investigating what may be causing them to proliferate; global warming and overfishing of fish species are two theories,” said Gillanders.

“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.”

The article can be found at: Doubleday et al. (2016) Global Proliferation of Cephalopods.


Source: University of Adelaide; Photo: damn_unique/Flickr/CC.
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