Black Gill Disease Blamed for Poor Shrimp Crop12 November 2013
US - Black gill has infected nearly half the shrimp caught in South Carolina since August. Shrimpers are blaming the disease for a poor crop and researchers are working to find a cause.
“The shrimp will survive; they will rebound. But this is a fishery on the edge of sustainability economically,” said Professor Marc Frischer, of the University of Georgia’s Skidaway Institute of Oceanography, one of the researchers.
“They’re already competing against a stacked market of farm-raised, imported shrimp. This may be the last straw.”
Black gill disease, or syndrome, is not lethal to shrimp by itself, but with a weakened ability to breathe, the shrimp are more vulnerable to predators. It is not harmful to humans, reports ThePostandCourier.
The disease has shown up in a year that already was trending toward a poorer catch; a fair spring crop was followed by a poor summer crop, mostly likely caused by heavy rains flushing shrimp too far and wide.
Black gill has tended to show up in at least some shrimp each year since it first was found here in 1999. But this year has been particularly bad. The outbreak apparently is worse the farther south you go; Georgia shrimpers are reporting as much as 90 per cent of the crop has black gill.
Black gill can be caused by a number of things from algae to heavy metals in the water, but this outbreak has been tied to a ciliate, a microscopic parasitic organism. It infects the gills, which respond by building a crust around it that turns the head black.
Not a lot is known about the ciliate. Frischer is working with S.C. Department of Natural Resources biologists and plans DNA sequencing at the Hollings Marine Laboratory in Charleston, to try to find where it came from — a first step to getting a handle on controlling the outbreaks. It’s possibly an invasive species, he said.
One thing researchers do know, it’s extremely infectious. A head removed from an infected shrimp and placed near a healthy shrimp, can infect it. Shrimpers themselves might be helping to spread the disease by heading the crop on the boat and discarding heads, Frischer said.
TheFishSite News Desk