Cod stocks in the North Sea and the Barents Sea may be predicted ten years in advance for the first time, thanks to a new statistical system. The corresponding research paper was published in Nature Communications Earth & Environment by an international team of researchers.
Previously, fisheries experts provided catch recommendations by estimating the size of current cod stocks and how much cod can be caught the following year without endangering stocks. These recommendations were made on a yearly basis and were used to negotiate fishing quotas internationally.
Providing catch recommendations in this way however did not factor in climatic change, changes in water temperature, and circulation and mixing, all factors that influence how well cod reproduce.
To update this recommendation system, researchers set out to create a statistical model that would link fish quantities to dynamic predictions of sea surface temperature based on climate models while also considering variance in fish stocks from mortality. Their final model starts with today’s temperature and carbon dioxide conditions before calculating how these factors will change over time, and how they translate into fish abundance and stock sizes.
To test the model, the researchers conducted retrospective forecasts from the 1960’s to the present. In doing so, they were able to correctly estimate fish stocks for ten-year periods since the early 1960’s. The researchers thus have confidence that their predictions for the next 10 years based on the model will be correct.
Their predictions for the next 10 years state that temperatures will continue to be high in the North Sea, meaning that cod stocks are unlikely to recover or reach earlier levels. As such, they say that catches are likely to remain low. The outlook is better however for the Barents Sea, where they say stocks can be managed sustainably.
"The 10-year estimates will help the fishing industry better plan catches in the future - so that cod stocks are fished sustainably and gently despite changes in climate," says Vimal Koul, lead author of the research.