Warming waters, disease threaten Georgia shrimp

https://www.ajc.com/lifestyles/environment/warming-waters-mysterious-parasite-warns-change-georgia-coast/wXGRYjfM3FTdJVR0xThK4M/?fbclid=IwAR1ul3cJnzo0j1El3igOgayYrwgM76LgR-ZdQmuk4ljkXvuy72V0Tk1dV-g

By Meris Lutz, The Atlanta Journal-Constitution
Dec. 1, 2019

The fall of 2013 should have been a blessing for Georgia shrimpers.

A bacterial infection had wiped out the Asian shrimp farms that drove many Americans out of business. Early sampling at the time indicated a bumper crop of white shrimp on the way. Many poured money into fixing up their boats in preparation for long, rewarding days on the water.

But the nets came up empty.

“They were gone,” recalled Dr. Marc Frischer, a microbiologist at the University of Georgia’s Skidaway Institute of Oceanography near Savannah. “There were no shrimp.”

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As shrimpers follow their crop north into colder waters, and a new shrimp parasite reaches epidemic proportions, scientists are investigating how changes in climate could influence the future of shrimp and shrimping in the Southeast.

“Temperature, current, rainflow — all of those are related to climate and all of those play very critical roles in the complicated biology and ecology of the system,” said Frischer. “Not just for shrimp, for everything.”

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Experts say there appears to be a strong correlation between black gill and climate conditions. While correlation does not equal causation, this theory is supported by experiments in the lab on the shrimp themselves.

In one study, changing water temperature by just two degrees had a huge impact on mortality rates for shrimp exposed to the parasite—a difference of up to 70 percent.

Coastal water temperatures in Georgia have increased by nearly five degrees over the past four decades, according to data collected by the state. Even with seasonal variation, the increasing trend is clear. Using a commonly employed statistical test developed by U.S. government scientists, the AJC concluded that such a consistent and steady increase is unlikely to arise randomly.

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