NC Wildlife Biologists Investigate Widespread Fish Kills after Hurricane Florence

Cape Fear River fish kill following Hurricane Florence 2018. Credit Kyle Rachels/NC Wildlife Resources Commission
Cape Fear River fish kill following Hurricane Florence 2018. Credit Kyle Rachels/NC Wildlife Resources Commission

Fisheries biologists with the North Carolina Wildlife Resources Commission continue to document widespread fish kills in eastern North Carolina in the wake of Hurricane Florence.

The fish kills are the result of significant declines in dissolved oxygen.  As of October 4, 2018, the rivers experiencing low dissolved oxygen levels and reported fish kills are:

  • Cape Fear River from Tar Heel to Southport
  • Sutton Lake near Wilmington
  • Northeast Cape Fear River from Kenansville to Wilmington
  • Black River from Garland to the Cape Fear River
  • South River from Garland to the Black River
  • Lumber River from Lumberton into South Carolina
  • Waccamaw River from the headwaters into South Carolina
  • Pungo River upstream of Belhaven
  • Neuse River from Goldsboro to Fort Barnwell
  • Contentnea Creek downstream of Hookerton
  • Trent River from Pleasant Hill downstream to the mouth at New Bern
  • White Oak River from the headwaters to Stella
  • Cashie River from Windsor to the mouth at Albemarle Sound
  • Roanoke River downstream of Highway 45 to the mouth at Albemarle Sound
  • Chowan River upstream of Winton

Many other rivers and streams, canals, lakes, and private ponds in eastern NC have also experienced dissolved oxygen declines and smaller, isolated fish kills.

As oxygen levels remain depressed, biologists expect the fish kills will persist for several more weeks.

Said Chad Thomas the Commission’s Coastal Region fishery supervisor:

“These fish kills, while unfortunate, are naturally occurring events that typically follow a major hurricane. Like we saw with Hurricane Irene in 2011 and Hurricane Isabel in 2003, low dissolved oxygen is the main culprit in these fish kills, rather than contaminants, pollution or other factors.”

Fish absorb oxygen from the water through their gills, and background oxygen levels of 5-6 ppm (parts per million) or higher are considered optimal for most species. Flood waters associated with Hurricane Florence inundated vast areas of swamp habitats that were naturally much lower in dissolved oxygen. As water levels recede, a flushing effect occurs. The result is a significant drop in dissolved oxygen in the mainstem rivers and creeks. When oxygen levels decline to 2 ppm, fish will become lethargic and often gasp at the surface. Thomas said:

“Many river basins have become anoxic, meaning they contain little if any dissolved oxygen. Numerous strandings of fish on roadways and adjacent to various water bodies have also been observed following substantial flooding.”

As water levels return to normal and water temperatures begin to cool, Thomas expects dissolved oxygen levels to gradually recover. Commission biologists will continue to monitor the affected water bodies through November to get a better understanding of the extent and severity of the fish kills. Next spring, they will sample the waters to determine fish species composition and abundance so they can determine strategies for recovery of fish stocks.  Thomas said:

“These coastal systems are resilient, and with time, the fish populations in the impacted waters will recover, as they did after Hurricane Irene in 2011.”

 

Source: Jodie Owen, NC Wildlife Resources Commission

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