Global warming: Where have all the sardines gone?

Trying to hack the climate by introducing fertilizers to induce alge bloom could have serious consequences.
Sardines and other commercially important fish are moving north in response to global warming.

Study tracks temperature-driven shift in Atlantic Ocean fish populations

Staff Report

FRISCO — For centuries, sardines, anchovies and mackerels have been critically important species for coastal communities, but global warming is chasing the fish northward. Some fishing towns may be facing make big economic adjustments in coming decades, according to researchers who carefully crunched the numbers for 40 years worth of fishing records.

The new study warned that the changes in such an important ecological group “will have an effect on the structure and functioning of the whole ecosystem.”

The North Atlantic has been a global warming hotspot, with ocean temps increasing up to 1.3 degrees Celsius in the past 30 years, affecting the  frequency and biogeography of sardine, anchovy and mackerel, all of which feed on phytoplankton and zooplankton and, in turn, are  the staple diet of large predators such as cetaceans, large fish and marine birds. These fish also represent a significant source of income for the majority of coastal countries in the world.

Until now, scientists had not managed to prove whether the changes observed in the physiology of the pelagic fish were the direct result of the water temperature or if they were due to changes in plankton communities, their main food source, which have also been affected by global warming and have changed their distribution and abundance.

The new study, published in Global Change Biology, developed statistical models for the North Sea area, confirms the great importance of sea temperatures.

To demonstrate the consequences of the warming of the seas, the research team analyzed 57,000 fish censuses from commercial fishing performed independently along the European continental shelf between 1965 and 2012, extracted from data provided by the International Council for the Exploration of the Sea.

The results reveal that sardines and other fish (with fast life cycles, planktonic larval stage and low habitat dependence) are highly vulnerable to changes in ocean temperature, and therefore represent “an exceptional bioindicator to measure the direction and speed of climate change expected in the near future.”

As the warming in the Atlantic speeds up, the fish are moving toward the North Sea and even into the Baltic.

 

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