Fish Size Offers Clues to the State of the Climate

A NSF graduate research fellow and collaborators have shown that, throughout the 20th century, warmer summer temperatures have limited the size of Atlantic cod along the Norwegian Skagerrak coast.

The health of commercial fish stocks is of growing concern as the climate changes. Atlantic cod (Gadus morhua) are listed as "vulnerable" by the IUCN (International Union for Conservation of Nature) Red List of Threatened Species.

The recent research shows that, if temperatures continue to rise, the negative effects of warmer summers on size of young fish will likely outweigh the positive effects of warmer springs, resulting in a negative impact on Atlantic cod populations in the Skagerrak.

Lauren Rogers, who received her doctorate from the University of Washington, spent six months as a Nordic Research Opportunity Fellow sponsored by NSF and the Research Council of Norway. Analyzing 91 years of data from surveys along the Skagerrak coast, she compared long-term records of fish size with historical data on water temperatures and found that that spring and summer temperatures had opposing effects on the size of young Atlantic cod. While warmer springs resulted in larger cod, warmer summers were often too warm, exceeding the optimum temperature for growth and resulting in smaller cod.

The results of this collaboration were published in the Proceedings of the National Academy of Sciences in January 2011 and highlighted in other news articles.