About 200 fish died last week in Davidson Pond, off Griffith Street. (David Boraks/DavidsonNews.net)

Gizzard Shad. Click to see a brochure about NC Shad. (SOURCE: N.C. Wildlife Resources Commission)

By DAVID BORAKS
DavidsonNews.net

Warm water and rapid algae growth are being blamed for an unusual fish kill last week at the pond in Roosevelt Wilson Park, off Griffith Street. Town and county officials say the recent warm, clear weather has spurred algae growth, which has reduced oxygen in the water, and likely caused the deaths of about 200 Gizzard Shad.

Davidson Public Works Director Doug Wright has been keeping in touch with county water quality experts as they investigate the incident, which a resident reported on June 19. He was a bit relieved at the explanation.

“It’s not any kind of herbicide or chemicals. We’re glad it’s not that,” Mr. Wright said in an interview.

He said officials are waiting for tests, but they’re pretty sure they will confirm the algae bloom and low oxygen as the cause. The next question is how the loss of the Gizzard Shad might affect other fish in Davidson Pond, which feed on the shad. Gizzard Shad grow up to 10-12 inches and up to 2 pounds, and can be a food source for larger fish, including bass,

“We want to make sure (the fish kill) doesn’t affect fish that feed on shad,” Mr. Wright said.

Two Mecklenburg County water quality specialists – Corey Priddy and David Buetow – have told Mr. Wright that they believe the warm water an algae are to blame. In an email Tuesday to Mr. Wright, Mr. Beutow said:

The cause of the low dissolved oxygen that led to the fish kill was most likely due to warm water temperatures and high algae growth in the pond. I am referring to suspended algae, or phytoplankton, which are the microscopic plants in the water that give it a green cast. The recent warm, clear weather and elevated nutrients in the pond are ideal conditions for algae growth. Suspended algae increase dissolved oxygen during the day when they photosynthesize but pull oxygen out of the water at night when there is no sunlight and they respire.

Mr. Wright said no more dead fish have been found since the incident last week.

Experts recommend that ponds have fountains or other aeration devices to help ensure oxygen levels. Visits to Davidson Pond this week found that the fountain there is working.

RELATED LINKS

N.C. Wildlife Resources Commission brochure on the types of shad in N.C. (PDF)

June 21, 2012, DavidsonNews.net, “Investigation seeks cause after 200 fish die in Davidson Pond.”