Climate change no threat to cod – Fishupdate.com

Climate change no threat to cod Published:  20 December, 2006

RESEARCH published online in a paper today suggests that climate change has had little influence on adult cod movements in the North Sea.

Scientists David Righton from the Centre for Environment, Fisheries & Aquaculture Science (Cefas) and Francis Neat from Fisheries Research Services (FRS) jointly investigated the thermal ecology of cod throughout the North Sea.

The recent warming of the North Sea has been accompanied by the decline of Atlantic cod (Gadus morhua L.) over the past 20 years. Whereas over-fishing has been a factor, cod distribution has been shown to be moving north. Other potential reasons for the shift could be changes in prey distribution or the fact that the southern component of this commercially important stock is more depleted than the northern.

Cod are highly mobile fish. Scientists conjecture that they might be expected to move to cooler habitats if global warming has created unfavourable habitats in the south. To test this theory, Neat and Righton compared the temperature experience of cod with independently measured sea-bottom temperature data.

Using “data loggers”, tiny electronic data storage tags (DSTs), the scientists tagged individual fish between 1999 and 2005. From 129 returned tags, it was found that most cod occupied a warmer fraction of the sea than was potentially available to them, despite cooler waters being within reach. Thus adult cod do not avoid warm water, suggesting that climate change is just one of many factors that influence cod distribution.

Cefas scientist, David Righton, said; “We’ve got some amazing individual-based data that provide us with information on how adult cod respond to thermal habitat changes. Probably for a number of complex reasons, cod don’t seem to avoid high temperatures. Our study shows that understanding the processes that drive the interaction between species and their environment is crucial to making predictions about how marine ecosystems will change in the future as climate changes.”

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