Hurricane Florence dumped more than 30 inches of rain in parts of coastal North Carolina, causing unprecedented flooding that triggered septic malfunctions, overflowed sewer systems and flushed wildlife fecal waste into rivers and sounds.

In anticipation of these impacts, the N.C. Division of Marine Fisheries preemptively closed all coastal waters to shellfish harvest beginning at sunrise Sept. 13, and some shellfish waters have yet to reopen.

The division never closed waters to fishing due to the storm, and the Department of Health and Human Services never issued a fish consumption advisory related to Hurricane Florence. Here’s why.

Shellfish — oysters, clams and mussels — are filter feeders, which means they gather food particles by pumping water through their gills almost constantly. As they feed, they also take in any bacteria and viruses present in the water and concentrate them in their gills and gut. Because the animals are consumed whole, if they contain high concentrations of bacteria or viruses, they could cause severe illness to the consumer. Therefore, it is mandatory to close shellfish waters after heavy rains that cause runoff or flooding that washes fecal waste into the waters. You can stay up-to-date on shellfish closures by going to the division’s Shellfish Polluted Areas Proclamations Page.

Fish (including shrimp and crabs), on the other hand, are biologically different. Typically, contaminants accumulate in fish tissue over time, and acute events, like hurricane flooding, do not result in significant increases of contaminants in fish that are consumed. However, caught fish should always be properly filleted, cleaned and cooked.

The Department of Health and Human Services does have standing fish consumption advisories (not related to Hurricane Florence) that are still applicable to the area. For more information, the DHHS Occupational and Environmental Epidemiology Branch webpage on fish consumption advisories has information on how fish consumption advisories are developed and what fish are safe to eat.