"Black gill parasite causes misery for shrimp and it’s hard to detect" By Nicole Pilson Coastal & Marine Resources Texas A&M AgriLife Matagorda County

   If you fish with shrimp or are in the shrimping business, you may have come across something rather peculiar. 
   You might have noticed that shrimp gills are black or dark in color - definitely not the norm for shrimp gills. 
   You try to clean it off in the water thinking it’s some mud or oil, and it just will not wash out. 
   So what is it and is it harmful to us? While this discoloration is harmless to you and I, it is harmful to the populations of shrimp and consequently those that depend on shrimp. 
   This plague on shrimp is called black gill.
   This phenomenon is caused by a parasitic ciliate, a single-celled organism. This condition first showed up in the 90s in Georgia and has since increased or declined with the seasons. 
   The ciliate affecting shrimp causes infected specimens to live about half as long as uninfected shrimp, and as you can imagine, this results in life cycles being cut short. 
   The gills of the shrimp turn black due to an immune response triggered that engulfs the parasites in the hope to eradicate it. 
   However, this increased gill pigmentation makes the shrimp more susceptible to predation because they are now easier to spot. 
   The shrimp also try to molt in another attempt to get rid of the pesky parasite. 
   Unfortunately, molting uses up a lot of the shrimp’s energy and the parasite is likely unbothered by the process. 
   The ciliate will switch to its free-swimming form and feed on the molted shell and wait for a new host. 
   This infection makes it harder for shrimp to breathe, and again, increases their chances of being preyed upon. 
   A lot of us may never see black gill in shrimp for a couple of reasons, the first being that shrimp might carry the parasite but be asymptomatic. 
   Depending on the stage and severity of the infection, the shrimp’s gill may not have darkened yet and we would have no way of knowing if we came across a sick shrimp. 
   Another reason is that many of us buy de-headed shrimp, so we definitely would have no chance of spotting the “disease.” 
   The heads of the shrimp are thrown overboard, which is great for marine scavengers but also potentially ensures that the ciliate can move on to new hosts. 
   There is great evidence showing the prevalence of black gill in Texas bays, but the research has not been done on gulf populations yet.
   In an effort to learn about more about this parasite and its scope, Texas Sea Grant has partnered with a local Texas Parks & Wildlife biologist and Palacios shrimpers. 
   Results will not be developed for quite some time, but we are eager to find out if this devastating ciliate is making its way to our beloved gulf shrimp. 
   Ridding our waters of the parasite is quite a big task, and frankly we may not be able to do very much to mitigate the spread completely. However, we can take small steps to ensure we are doing our best to protect shrimp populations. Whether its bait shrimp or table shrimp, be mindful of where you discard the heads. 
   If you can, save the unwanted heads on your boat until you can throw them away on land. 
   This is also an anticipated conversation we will have with shrimpers in working with them to find ways of safely removing heads from their vessels. 
   If you are at home and keep your heads to later throw in the bay - hold onto them! 
   Shrimp heads and shells, mixed with a few other ingredients, can make a delicious stock full of vitamins and minerals and great for making soups or adding flavor to various dishes. 
   The parasite does not affect the quality or health of tail meat and the ciliate does not cause illness in humans. 
   So do not hesitate to keep supporting the Texas shrimping industry! 

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