Pacific Northwest Research Station

You've probably heard of, or maybe even seen, the massive die-offs of fish that sometimes occur in lakes and coastal areas worldwide. But do you know what one major cause of fish die-offs is? Hypoxia, or extremely low levels of dissolved oxygen in water. When water is hypoxic, the low amount of oxygen can severely damage, and even kill, hundreds to thousands of fish at once.

In Alaska, scientists observed significant salmon die-offs in rivers right before the fish were able to spawn and they suspected hypoxia was the culprit. Pacific Northwest Research Station fish biologist Ryan Bellmore collaborated on a study investigating hypoxia in Alaska and found that high salmon densities in streams along with low stream flow best predicted hypoxic conditions. This work can help fisheries managers better manage salmon populations.

Check out the complete story below and view a short video on why understanding hypoxia is important to fisheries management.