What Happened to the Pacific Grey Cod?

Why Did One of Alaska’s Most Valuable Fisheries Crash?

In October 2017, the National Oceanic and Atmospheric Administration (NOAA) made a shocking announcement. Pacific cod (or grey cod) stocks in the Gulf of Alaska had declined 71% since 2015 and 83% since 2013. Cod, once one of the most plentiful fish in Alaskan waters, suddenly became a rare catch, devastating one of the most lucrative commercial fisheries in the state. Biologists scrambled to learn why cod were dying and why the few cod caught weighed less than normal and appeared malnourished.

While researchers yet do not have empirical evidence to support their theory, they have a good idea why cod populations have crashed. During the winter of 2013/2014, scientists mapped an unusually warm, large, circular body of seawater in the North Pacific Ocean. This mass of water didn’t cool as winter progressed but instead hovered several degrees above the normal winter temperature. Scientists nicknamed the mass of warm water the “Blob.” In February 2014, the Blob remained 4.5° F (2.5°C) warmer than the average February ocean temperature.

Warm water temperatures persisted throughout 2014, and oceanographers noted these were the warmest temperatures ever measured in the North Pacific Ocean since climatologists began recording ocean temperatures. Along with these warm water…