Fall black gill cruise rolls out new research

The University of Georgia Skidaway Institute of Oceanography entered the fourth year of its black gill research program with a daylong cruise on board the Research Vessel Savannah and the introduction of a new smartphone app that will allow shrimpers to help scientists collect data on the problem.

Led by UGA scientists Marc Frischer, Richard Lee, Kyle Johnsen and Jeb Byers, the black gill study is being conducted in partnership with UGA Marine Extension and Georgia Sea Grant, and is funded by Georgia Sea Grant.

Black gill is a condition Georgia shrimpers first noticed in the mid-1990s. Many shrimpers have blamed black gill for poor shrimp harvests in recent years, but until Frischer began his study, almost nothing was known about the condition. Now the researchers know black gill is caused by a parasite—a single-cell animal called a ciliate—although the exact type of ciliate is still a mystery.

The October cruise had three goals. The first was simply to collect data and live shrimp for additional experiments.

 

“We were able to collect enough live shrimp in good shape to set up our next experiment,” Frischer said. “We are planning on running another direct mortality study to investigate the relationship between temperature and black gill mortality. This time, instead of comparing ambient temperature to cooler temperatures as we did last spring and summer, we will investigate the effects of warming.”

Researchers Marc Frischer (UGA Skidaway Institute), Brian Fluech and Lisa Gentit (both UGA Marine Extension and Georgia Sea Grant) examine shrimp for signs of black gill.

If his hypothesis is correct, Frischer believes researchers would expect that raising fall water temperatures to warmer summer levels in a laboratory setting will induce black gill associated mortality in the shrimp caught in the fall.

Those studies will be compared to those that are being conducted in South Carolina in a slightly different manner. Frischer expects the results should be similar.

“However, as it goes with research, we are expecting surprises,” Frischer continued. “We also collected a good set of samples that will contribute to our understanding of the distribution and impact of black gill.”

A second goal was to introduce and begin field testing a new smartphone application developed by Johnsen. The app is intended to be a tool that will allow shrimp boat captains and recreational shrimpers to assist the researchers by filling some of the holes in the data by documenting the extent of black gill throughout the shrimp season. The Georgia Department of Natural Resources conducts surveys of the shrimp population up and down the coast throughout the year. However, those surveys do not provide the researchers with the rich data set they need to really get an accurate assessment of the black gill problem.

A sample screen shot of the black gill smartphone application.

“Instead of having just one boat surveying the prevalence of black gill, imagine if we had a dozen, or 50 or a hundred boats all working with us,” Frischer said. “That’s the idea behind this app.”

The fishermen will use the app to document their trawls and report their data to a central database. Using GPS and the camera on their smartphone, they will record the location and images of the shrimp catch, allowing the researchers to see what the shrimpers see. If repeated by many shrimpers throughout the shrimping season, the information would give scientists a much more detailed picture of the prevalence and distribution of black gill.

“The app is complete and available on the app store, but we are still in the testing stages,” Johnsen said. “We want to make sure that it will be robust and as easy to use on a ship as possible before widely deploying it.”

Recruiting, training and coordinating the shrimpers will be the responsibility of UGA Marine Extension and Georgia Sea Grant.

“I think it should be entirely possible to at least have a small group of captains comfortable and ready to start using it when the 2017 season begins,” Frischer said.

Johnsen is excited about the app for what it can provide to the shrimping and research community, but also the implications it has for using apps to involve communities in general.

“There is still work to be done to improve the usability of these systems,” he said. “But I’m confident that we are going to see an increasing number of these ‘citizen science’ applications going forward.”

The final aim of the cruise was to bring together diverse stakeholders, including fishery managers, shrimpers and scientists, to spend the day together and share ideas.

“This was a good venue for promoting cross-talk among the stakeholder groups,” Frischer said. “I had many good conversations and appreciated the opportunity to provide a few more research updates.”

Georgia DNR’s Pat Geer sorts through the marine life caught in a trawl net.

Frischer says he thinks the communication and cooperation among the various stakeholder groups has improved dramatically since the beginning of the study. He recalled that when the study began in 2013, tensions were high. Shrimpers were angry and demanded that something be done to address the problem of black gill. Meanwhile, fishery managers were unclear if black gill was even causing a problem and frustrated that no one could provide them any reliable scientific advice. The research community had not been engaged and given the resources to pursue valid investigations.

“In 2016, we still have black gill. The fishery is still in trouble, but it does feel like we are at least understanding a bit more about the issue,” Frischer said. “Most importantly, it is clear that all of us are now working together.

“My feeling is that the opportunity for us to spend a day like that together helps promote understanding, communication and trust among the shrimpers, managers and researchers.”

Skidaway Institute scientists study black gill in shrimp

Scientists at the University of Georgia Skidaway Institute of Oceanography are investigating black gill in shrimp, a condition Georgia shrimpers are blaming for an ongoing downturn in shrimp harvests. Very little is known about black gill, so professors Marc Frischer and Dick Lee are working with shrimpers and a number of agencies in a collaborative project to answer some key questions about the condition.

R/V Savannah crewman Chris Keene prepares to dump a load of shrimp and other marine life for inspection and study.

 Black gill is a symptom of a health problem in the shrimp. The affected shrimp are easy to identify because they exhibit large black areas on their gills, which are right behind their head. The black gill has no effect on the edible qualities of the shrimp. Shrimp affected with black gill are perfectly safe to eat, and the condition has no effect on the taste of the shrimp.

 Black gill has been an issue for pond-raised shrimp for more than a decade, but it has only been within the last several years it has become a problem for wild shrimp fishermen. Black gill can be triggered by several factors among pond-raised shrimp. Skidaway researchers believe black gill in wild Georgia shrimp is caused by a microscopic parasite classified as a ciliate—a single cell animal with tiny hairs called cilia that help them move. The scientists don’t know yet exactly which ciliate is to blame. The blackened gills are the result of the shrimp’s immune system reacting to the ciliate invasion. It creates black nodules around the invasive ciliates in the shrimp’s gills.

Three shrimp with black gill.

 Beyond the blackened gills, it is not known how the condition affects the health and morbidity of the shrimp. Shrimp shed their gills through their normal molting process. Scientists suspect the parasite triggers a molting response, causing the shrimp to shed their shells and gills repeatedly in an effort to rid themselves of the parasite. This may cause them to use up extra energy and leave them stressed and vulnerable to predators. Examination of infected gill tissue also reveals the ciliate can damage the shrimp gill and directly impact the ability of the shrimp to breathe.

 The Georgia Department of Natural Resources statistics indicate that at its peak in October 2013, 40 percent of the shrimp captured in its surveys had black gill. Shrimpers are blaming black gill for reduced catches last year and so far this season.

 “That may turn out that is the case, or it may not,” said Frischer. “As of right now, we have no scientific evidence to support it. That would be a good question to address in an additional research project beyond this one.”

 Frischer, Lee and their collaborators will try to determine how black gill is transmitted, and if it is infectious. They also want to determine the distribution of the condition and its causative agent, and also see if the parasite exists in other crustaceans, in sediments or in the water.

 According to Frischer, the black gill ciliate may always be present in the shrimp and probably other places too. For most of the year, shrimp are able to handle it. “However, in the late summer the water warms and the oxygen level drops, the shrimp may become stressed,” he said. “This may stress the shrimp and allow the parasite to proliferate.”

 The two-year project will be sponsored by a $140,000 grant from Georgia Sea Grant, a unit of UGA Public Service and Outreach. The funding is not yet official, but Skidaway Institute scientists began their work early because this is the time of year when black gill is prevalent. 

 Anna Walker of Mercer University is working with the Skidaway Institute researchers to conduct pathological tissue studies.

 Other collaborators on the project include UGA Marine Extension Service, Georgia Department of Natural Resources – Coastal Resources Division, the Georgia Shrimp Association, the South Carolina Department of Natural Resources, Southern Shrimp Alliance, the Florida Fish and Wildlife Conservation Commission and the North Carolina Division of Marine Fisheries.