Historical data gives up secrets of Britain’s favorite fish

U.K. fisheries survey logbooks from the 1930s to the 1950s have been digitized for the first time, revealing how cod stocks have responded to changing temperatures in the last century.

Scientists at the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) and the University of Exeter found that, at the time, the warm seas experienced around Norway benefitted the cod, similar to the conditions there today.

Most of the cod consumed in the United Kingdom comes from northern seas, including the Barents Sea around Norway, because the stocks there are currently at record highs. Cod stocks were also big in the middle of the last century and this new research, published in PLOS ONE – a peer-reviewed open access scientific journal published by the Public Library of Science – reveals that the environmental conditions at the time contributed to the change.

Meanwhile, cod diet data found that the environment also affected their food preferences each year – between capelin, herring, crustaceans and cod cannibalism.

CEFAS holds many records from historical survey cruises, many of them in the form of paper logbooks. A recent program of work concentrated on cataloguing and digitizing these documents, where possible, to ensure that they are not lost and can be made freely available.

More of CEFAS’ data, with the exception of data owned by industry, will continue to be made available this year.

The Barents Sea surveys were mainly carried out by the steam vessel RV Ernest Holt, which was commissioned especially to withstand Arctic conditions. The newly-rescued data allows scientists to understand how fisheries in the region have responded to temperatures from the 1930s through to the present day.

Scientists at the time knew that the cod were being affected by their environmental conditions, but digitizing this data has allowed modern techniques to delve into the responses of cod to changes in their environment and diet.

“Historical data such as this are so important in understanding climate change and variability. We know from anecdotal evidence that fisheries have varied in the past but it is rare to have such comprehensive datasets going back to the early 20th century. These logbooks, along with others still held by CEFAS, reveal unique insights into the state of fish stocks and the environment in the past century, and enable us to put more recent changes into context,” said Bryony Townhill, CEFAS’ marine climate change scientist.


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