Feral Hogs: An Aquatic Nuisance Species Weakens the Resiliency of Coastal Marshes

By Rebecca Brown and Jim Page

Wilbur.  For many of us who grew up watching Charlotte’s Web, the site of America’s Favorite Pig is a welcome one.  However, though Charlotte’s porky friend was certainly cute and friendly, we have come to learn in our adulthood that such is not always the case with pigs and hogs, specifically for those who have no farm to call home.  Feral hogs, or wild pigs, have caused some of the most significant negative impacts on our ecosystems.  In fact, some scientists say wild pigs are the greatest vertebrate modifier of natural communities in the United States. 

Now found throughout the state of Georgia, these menacing pests create a multitude of issues.  A walking vacuum, they will eat just about anything that can fit into their mouth.  In the process of searching for food, they root around in the soil, causing significant destruction to many of our native plant communities, some of which may be endangered or threatened. 

Their destruction isn’t just a byproduct of their rooting and feeding behavior; sometimes, it is a direct consequence of their feeding behavior.  Scientists have learned that one of the favorite foods of wild pigs residing on Georgia’s barrier islands is also one of Georgia’s most threatened species:  sea turtles, specifically their eggs.  Research has shown that wild pigs will often use their enhanced sense of smell to locate a sea turtle nest, dig them up, and eat the eggs, thereby negatively impacting a sea turtle population already struggling to rebound. Though such negative impacts on sea turtles along our coast have been known for years, it wasn’t until recently that additional coastal impacts by these pests were realized.   A recent study in the marshes of the Sapelo Island National Estuarine Research Reserve has discovered feral hogs can also reduce the resilience of our southeastern United States salt marshes.

Feral hogs have a hefty appetite for ribbed mussels, a bi-valve that grows together in mounds and is commonly found in the marshes of Georgia.  These mussels have a non-trophic relationship with cordgrass, or Spartina, that regulates the ecosystem structure and resilience of salt marshes.  Scientists have learned that cordgrass and ribbed mussel have a positive mutualistic relationship in that the waste produced by the mussels provides nutrients for the growth of cordgrass and the cordgrass provides substrate and shade for the mussel.

Though their aesthetic beauty is well documented in the poetry of Sidney Lanier, cordgrass serves a much more important purpose.  Cordgrass is the base of the coastal marsh ecosystem that provides many ecosystem services. 

Additionally, cordgrass are essential for saltmarsh recovery after a catastrophic event such as a severe drought.  Recovery time after a large die-off of cordgrass can be a few years when ribbed mussels are present, as compared to many decades to recover when mussels are not present.

The discovery of the impacts of increased mussel predation by wild pigs along the coast is certainly alarming.  The loss of ribbed mussels can significantly weaken the resilience of our coastal marshes and thereby reduce the ecosystem services these marshes provide us.  Our coastal ecosystems are already facing increased pressure as global climate change increases the length and severity of droughts, increases storm intensity and frequency, and causes sea levels to rise. The facilitating species in non-trophic positive interactions can buffer against abiotic stress, widen niches, increase population densities, and strengthen ecosystem multi-functionality.  As a result of the learned negative impacts these pot-bellied pests can create, management plans created by resource managers need to adjust accordingly.  This means taking a wider approach to factor in how invasive species like wild hogs can alter non-trophic positive interactions (e.g. cordgrass and ribbed mussel).  We must consider how we as resource managers can prevent when possible and overcome when challenged with these unfortunate scenarios.  If we don’t, we may be left with less than nothing, and even a pig like Wilbur knows that’s the lowest you can go.

More Information: https://www.nature.com/articles/s41467-021-26504-4 

Boating Safety: Don’t Become a Statistic

An estimated 100 million Americans go boating each year. In 2020, the Coast Guard counted 5,265 accidents that involved 767 deaths and 3,191 injuries. Compared to 2019, the number of accidents increased 26.3%, the number of deaths increased 25.1%, and the number of injuries increased 24.7%. Where the cause of death was known, 75% of fatal boating accident victims in 2020 drowned. Of those drowning victims with reported life jacket usage, 86% were not wearing a lifejacket. Where instruction was known, 77% of deaths occurred on boats where the operator did not receive boating safety instruction. Only 12% percent of deaths occurred on vessels where the operator had received a nationally-approved boating safety education certificate. Operator inattention, operator inexperience, improper lookout, excessive speed, and machinery failure rank as the top five primary contributing factors in boating accidents. (americanboating.org)

Do you consider yourself a competent boater?

You are headed toward open water and we see only one green buoy ahead, would you keep the buoy on your right side or keep the buoy on your left side? You are boating at night and you see a red and white light, would you maintain your current speed or slow down?

Georgia Boating Laws require all persons born on or after January 1, 1998, that operate any motorized vessel on the waters of the state must have completed a boat education course approved by the department prior to such operation. Even if you are of the age that you are not required to take the course, you should at least review the Georgia boating laws and responsibilities. A person is exempt if he or she is:

  • a person licensed by the U.S. Coast Guard as a master of a vessel;
  • a person operating on a private lake or pond;
  • a non-resident who has in his or her possession proof that he or she has completed a NASBLA-approved boater education course or equivalency examination from another state.

You can take a boating education course in a classroom setting with the Department of Natural Resources, the United States Coast Guard, or the United States Power Squadrons. You can also take one of our approved online courses from the service providers listed below under On-Line Courses. Some courses have an associated cost, while others may be free.

More information: https://gadnrle.org/boating-education

Lake Lanier, Georgia

Preventing Accidental Introduction of Invasive Species

Several fisheries professionals, marina owners, fishing guides, and others attended the Watercraft Inspection and Decontamination Training (WIT) workshop the first week of May at Red Top Mountain State Park. Lead instructors Dee Davis (Pacific States Marine Fisheries Commission) and Colleen Allen (National Park Service Aquatic Nuisance Species Coordinator) shared their vast knowledge of aquatic invasive species and how to prevent them from entering our state. Participants learned how to thoroughly inspect watercraft for zebra and quagga mussels and other aquatic nuisance species from stern to bow and the trailer too. Proper decontamination procedures were demonstrated onsite and participants had an opportunity to practice what they had learned.

Hazard Analysis and Critical Point (HACCP) training was also held at Red Top Mountain State Park that same week. HACCP examines our day-to-day activities (i.e. fish sampling, raising and/or stocking fish, habitat restoration projects, etc.) to determine if and when invasive species might be unintentionally moved. HACCP helps to identify the most effective opportunities during these activities to reduce the risk and the specific control measures that are needed. After learning the steps of HACCP the participants separated into individual teams to design a HACCP plan for an activity of their choice. The lead instructors, Cindy Williams (US Fish and Wildlife Service) and Colleen Allen (National Park Service) provided effective feedback to each team as they presented their plans.

Aquatic Plant Treatment Survey

The Small Impoundments Technical Committee is planning to host an aquatic plant workshop at the 2023 SDAFS annual meeting. Our goal is to provide identification as well as up-to-date control information for the most problematic aquatic species we are faced with within the Southeast. By polling SDAFS representatives from each state, we have developed a list of the top 23 problematic aquatic plants in southeastern impoundments. As new products and techniques are being used to control aquatic vegetation in both private and public water bodies in the Southeast, the informational literature is outdated. Therefore, we are polling professional applicators across the Southeast to gather more up-to-date control information that can be available to applicators. Please use this form and answer the questions for each plant listed below based on your own personal experiences, and in as much detail as you are willing.

NOTE: Obviously, choosing the best and most comprehensive weed control program for a particular body of water can be very subjective and requires a level of experience literature can’t provide. This poll is just intended to provide the best biological and chemical tools available to battle each plant species. Thus, for now, there is no need to mention other techniques such as retreatment, combining biological and chemical, shading with fertilization or dyes, deepening shallow areas, nutrient reduction, etc. There is no need to indicate any state restrictions for biological control or chemical control agents. Applicators should be aware of this already. Also, refrain from listing specific chemical application rates or possible water quality/toxicity issues as this information is listed in the product label and should be left to the discretion of the applicator in each situation.   

ANOTHER NOTE: You will be asked to provide the most effective chemical treatment for each plant; however, a different chemical treatment may be more practical or affordable in some situations. Provide that info in the “Additional Notes or Comments” section at the bottom. Also, if your control information for one plant is the same as another plant on the list, then you can just indicate that besides the plant’s name. If you have no experience controlling a particular plant, just leave blank.

Link: https://forms.gle/TEoQRESKwq1Eonrh9

Aquatic Invasive Species Training

Two training workshops are scheduled for May 2022 at Red Top Mountain State Park.

The Georgia DNR Wildlife Resources Division is partnering with the Pacific States Marine Fisheries Commission to host a FREE training session to educate marina owners, boat owners, bait shop owners, fishing guides, and others about helping prevent the spread of Aquatic Invasive Species in our state. Zebra mussels and other aquatic invasives continue to be a threat, and our best chance to minimize their impacts is to prevent their introduction. Join us and learn how YOU CAN HELP in these efforts. Space is limited. Register online: https://form.jotform.com/220475746059159

Click on the image below to download the PDF

The Georgia DNR Wildlife Resources Division is partnering with the U.S. Fish and Wildlife Service to host a Hazard Analysis & Critical Control Point (HACCP) training session. This is a valuable training session for anyone who works with natural resources field projects, manages property and/or facilities, manages or produces wildlife, fish, or terrestrial plants species on state, federal, or private lands including hatchery operations. This is a FREE course and space is limited and on a first-come, first-served basis. Anyone interested needs to register online (https://arcg.is/vu91x)

Click on the image to download the PDF

WHD and IHNV Found in Georgia

The Georgia Department of Natural Resources Wildlife Resources Division (WRD) announced on August 21, 2021, they are investigating Whirling Disease (WHD) and Infectious Hematopoietic Necrosis Virus (IHNV) in the hatchery-raised trout at both the Buford and Summerville trout hatcheries. Preliminary test results were positive for both hatcheries. Georgia WRD is taking steps to prevent the spread of these infectious diseases and has temporarily suspended the stocking of trout and is collecting more samples for disease analysis from the hatchery fish as well as wild populations in the Chattahoochee River downstream of the Buford Hatchery. Additional steps being taken include investigating the source for both pathogens and identifying disinfectant methodologies for treating the hatcheries. These are the first documented cases in Georgia.

Whirling disease is an infectious disease of salmonid fish, caused by Myxobolus cerebralis, a microscopic parasite, was first discovered in the U.S. in 1958 and is currently found in several states. Up until now, the closest outbreak to Georgia is when it was discovered in North Carolina’s Watauga River in 2015. Physical symptoms of WHD include blackened tail, whirling behavior, and deformities of the head and spine. Whirling disease does not infect humans, mammals, or fish that are not members of the salmonid family.

The disease IHNV is an infectious disease of salmonids. It was first recognized in the 1950s in sockeye and Chinook salmon. Young fish are more susceptible, and those that survive may become carriers of the virus and shed IHNV virus particles in their feces, urine, and external mucus. Symptoms of fish infected by IHNV include darkening, protruding eyes, pale gills, lethargy, distended abdomen, and abnormal swimming behavior. Humans are not susceptible to becoming infected by IHNV and fish with IHNV can be consumed.

Both of these diseases can be detrimental to Georgia’s trout species. Mortality rates are very high in both hatchery-raised trout as well as our wild trout populations. Visit the WRD website for more information about these invasive diseases and learn more about what you can do to help prevent the spread of WHD and IHNV. https://georgiawildlife.com/ans#diseases

Georgia Chapter 2021 Outstanding AFS Small Chapter

The Chapter was notified early August that we were the recipients of the 2021 Outstanding AFS Small Chapter Award. The Outstanding Chapter Award recognizes outstanding professionalism, active resource protection, and enhancement programs, as well as a strong commitment to the mission of the Society.

The award will be officially announced during the business meeting at the 2021 AFS Annual Meeting in Baltimore.

This prestigious award is a tribute to many people’s hard work and dedication, particularly the 2020 ExCom and Committee chairs. The rest of the country is learning what many of us have known for some time- we have a truly inspiring and talented group of fisheries professionals committed to conserving, managing, and improving our aquatic resources for today and the future.

As part of the application process, we had to answer the question – What makes your chapter unique and why is it outstanding? Our answer…

The Georgia Chapter possesses a unique sense of cohesiveness and can-do spirit among its professional, faculty, and student members, which helped us not only “get through” an unprecedentedly difficult year but rise to the challenges by adopting new modes of communication, education, and networking. As a result, our membership rolls, meeting attendance, outreach footprint, fundraising, and sense of camaraderie hardly missed a beat in 2020. In fact, we were able to reach an even larger audience, including citizens and potential fisheries recruits whom we might not have reached under traditional circumstances. Although every unit of AFS faced similar Covid-related issues, we are particularly proud of what we were able to accomplish in 2020. These accomplishments are detailed in the sections below and the attachments provided. In brief, they include (1) ramping up our information-dissemination campaigns through adding active Twitter and Instagram accounts (we already had Facebook) and periodic blog posts on topics like aquatic nuisance species and aquatic connectivity, (2) working with the GA DNR to develop and fund educational media (digital flyers, posters, and teaching workbooks) on various fishy topics, (3) developing a new set of web-based resources to connect Georgia high-school and college students to fish-related programs and faculty at colleges throughout the state, and to better understand what skills are needed for different careers in the fisheries field, and (4) for our student subunit at UGA, broadening the monthly seminar series to a much more geographically widespread field of guest speakers, thanks to using a Zoom virtual meeting format. Although we hope 2021 sees the restoration of more in-person interaction, we learned a number of useful lessons and skills in 2020 that we think maintained our effectiveness as a chapter and will enhance our relevance and reach moving forward.

The rest of the country is learning what many have known for some time- we have a truly inspiring and talented group of fisheries professionals committed to conserving, managing, and improving our aquatic resources for today and the future.

Decades of Detective Work Highlighted on the SciShow

Last year Susan Wilde, professor at the University of Georgia Warnell School of Forestry and Natural Resources, along with an international research team finally discovered the cause of avian vacuolar myelinopathy (AVM).

This mystery began in 1994 when dozens of dead bald eagles were discovered along DeGray Lake in Arkansas. During a necropsy, lesions were discovered on the brain around the myelin sheath which impacted communication to the nerve cells.

The cause of AVM was a mystery. It seemed to occur only in some freshwater reservoirs in the southeastern part of the United States. Scientists focused on the environmental conditions in AVM-positive waters. They suspected a connection between the non-native invasive aquatic plant Hydrilla verticillata and AVM. Susan later identified a cyanobacterium on the leaves of the hydrilla in 2005. She named the bacterium Aetokthonos hydrillicola (“eagle killer that grows on Hydrilla”). They suspected eagles were preying upon coots and other animals that fed upon the hydrilla and then themselves succumbing to the effects of AVM. The problem was they could not reproduce the toxin in the lab.

Using a more sensitive spectrometer, Timo Niedermeyer, a chemist with the University of Halle-Wittenberg in Germany, was able to identify a substance that is only made on the leaves where the cyanobacteria grow. He revealed the presence of a brominated molecule. The production of this toxin depends on the bromide in the water. This compound was named aetokthonotoxin (“poison that kills the eagle”).

The next step – find out where the bromide is coming from.

More information: Case closed on decades old mystery of American bald eagle deaths

SciShow, a web series hosted by Hank Green with over 6 million subscribers, on June 21 published a short video about this story.

Attention Aquarium Owners


It was March 3, 2021 when wildlife agencies all across the United States were issued a warning about the discovery of zebra mussels found in aquarium moss balls.  After further investigation viable zebra mussels were found in multiple pet stores including Georgia.  Although zebra mussels have established populations in numerous locations in the U.S. Georgia has been lucky enough to keep them out of our waterways.

The pet stores have removed the moss balls from the shelves, but some people may have purchased contaminated moss balls.  It is important you check your aquariums if you have purchased moss balls in 2021.  There are steps you can take to remove them from your aquarium and dispose of them properly.  Detailed instructions for disposal of the moss balls and zebra mussels and how you can sanitize your aquariums can be found at https://www.fws.gov/fisheries/ANS/zebra-mussel-disposal.pdf.  NEVER DUMP YOUR AQUARIUM CONTENTS IN ANY LOCATION WHERE THEY COULD REACH LOCAL WATERWAYS.  https://georgiawildlife.com/ans

Zebra mussels are an aquatic invasive species that get their name from their dark zig-zag stripes.  They are a freshwater bivalve that has a maximum shell size of about 3 centimeters, and are usually found in large clusters. They are native to the Black, Caspian, and Azov Seas.

Zebra mussels probably arrived in the Great Lakes in the 1980s via ballast water that was discharged by large ships from Europe. They have spread rapidly throughout the Great Lakes region and into the large rivers of the eastern Mississippi drainage. They have also been found in Texas, Colorado, Utah, Nevada, and California.

One unique feature the zebra mussel has that our native mussels lack are byssal threads extending from underneath their shell that allow it to attach to hard objects, surfaces, or other mussels.  Zebra mussels are suspension feeders, eating phytoplankton, small zooplankton, large bacteria, and organic detritus by filtering the water and straining out the edible material.

Zebra mussels can cause damage in many ways.

  • They filter out algae that native mussels, fish, and other primary consumers need for food.
  • Clutches of zebra mussels will attach to native mussels causing the native mussel to starve.
  • Power plants spend millions of dollars removing zebra mussels from clogged water intakes.
  • They can damage boats by encrusting boat hulls and clog water systems used in boat motors

Learn more about zebra mussels and how they impact aquatic ecosystems and the economy

Threats to Our Aquatic Ecosystems

Written by Jim Page and Rebecca Brown

Aquatic Nuisance Species.  When many folks in Georgia think of those terms, several species may immediately come to mind: flathead catfish, spotted bass, hydrilla, water hyacinth, snakeheads, or blueback herring, just to name a few.  While each of these are classic examples of aquatic nuisance species (ANS) that have been found in Georgia, there are other ANS that occur here that may not be at the tip of the tongue.  Two of these critters are animals that impact both our aquatic AND terrestrial ecosystems:  nutria and feral hogs.   

The Swamp Rat

It’s easy to think of fish when discussing ANS, but rarely do people think about the “swamp rat” that also bears the ANS title.  Native to South America, nutria is a large rodent similar to a cross between a beaver and a muskrat, having a long slender tail and webbed feet.  Introduced into the U.S. during the early 1900’s by fur traders, it was believed that the species would boost the fur industry and generate easy money.  Nutria were kept and raised in captivity in several locales throughout the U.S. as fur-traders banked on the species being the future of the fur industry.  However, the crash of the fur trade brought about the release of hundreds/thousands of nutria nationwide.  The subsequent consequences of such releases were felt soon after.  A voracious eater, these herbivores can consume 25% of their body weight each day (similar to grass carp) munching on the roots of wetland vegetation.  The consumption of these roots caused historical wetlands to transition into open water habitat.  Additionally, the species was found to tunnel along the banks of streams and rivers, causing damage and increasing soil erosion.  Thus, what started as a release with no intentional harm of a cute furry critter resulted in significant ecological impacts and the loss of precious wetlands around the country.  The impacts of nutria continue to this day, and the International Union for Conservation of Nature (IUCN) lists the nutria as one of the top 100 world’s worst invasive species.


The Opportunistic Omnivore

Unfortunately, nutria were not the only furry critters to be introduced into the U.S. that have ended up being a nuisance in the aquatic world.  As early as the early 1500’s, early European settlers brought with them domestic pigs.  Unfortunately, some of these pigs escaped captivity and began life anew in the wild.  The additional introduction of wild boar into the U.S. by hunters in the 1900’s resulted in what we now have today:  a feral swine population which is a mix of wild boar, escaped domestic pigs, or a hybrid of the two. 

For many of us, the memories of Wilbur in “Charlotte’s Web” makes us question what can be so wrong with have these potbellied porkies running loose in our ecosystem.  Though they may seem innocent, feral swine, or wild pigs, have caused some of the most significant negative impacts to our ecosystems.  In fact, some scientists say wild pigs are the greatest vertebrate modifier of natural communities in the United States.  A walking vacuum, they will eat just about anything that can fit into their mouth.  In the process of searching for food, they root around in the soil, causing significant destruction to many of our native plant communities and agricultural crops.  The USDA estimates feral pigs cause around two billion dollars of damage each year!

The feeding habits of feral pigs have reduced plant and forest communities and caused an increase in soil erosion.   Adding to the damage is their love for wallowing in moist soil located in and near riparian zones and wetlands, destroying vegetation and loosening the soil in these sensitive areas.  Loosened soil is later washed into local streams and rivers, creating sedimentation and water clarity issues.  Additionally, the waste from pigs contains vectors for disease and nutrients which are added to waterways as part of surface runoff.  Too many nutrients can cause algal blooms or hypoxic zones, which can easily lead to a fish kill.   

The aquatic impacts of feral swine are not limited to freshwater ecosystems.  Since their arrival onto barrier islands along the Georgia coast hundreds of years ago, feral pigs have created significant problems in the marine ecosystem.  In addition to destroying plants on these island ecosystems, the feral pig has created significant harm to one of our most treasured coastal inhabitants – sea turtles.  Egg-bearing sea turtles utilize the beaches of barrier islands for nesting, digging shallow holes above the high-tide mark and depositing several dozen eggs before covering them up and returning to the ocean.  The keen nose of the feral swine has proven to be efficient in detecting the nest of these endangered and threatened turtles, and upon discovering a nest feral pigs will dig up the nest and destroy the eggs.  Such destruction can have detrimental impacts to the stability of sea turtle populations and to our continued efforts to protect them.  

Feral pigs in South Georgia

Our Choices

The introduction of ANS species like feral swine and nutria have taught us many lessons, perhaps none more important than the fact that releasing species in areas outside their native range can have devastating ecological and economic impacts.  Though the introduction of these 2 species was not done with ill intention, it should be a lesson to us that such actions, well intended or not, can create significant challenges and hardships for our native species and environments.  As humans, it is the responsibility of each of us to aid in the proper management of the ecosystems in which we live and call home.  We need protection of sea turtle nests if growth and sustainability of the species our goal.  We need protection of our sensitive wetlands and other terrestrial habitats susceptible to destruction by introduced species like nutria.  We need stable plant communities along riparian zones to reduce the amount of sediments that are washed into our waterways during rainfall, creating turbidity issues and reducing the amount of sunlight in the water needed by plants for photosynthesis.  Sediment pollution in aquatic ecosystems can clog fish gills, causing increased stress for and decreased ability of the fish to resist disease.  An excess of suspended sediments can decrease visibility for visual predators like trout and black bass species.  Eventually these suspended sediments begin to settle and blanket gravel beds with sediments, possibly covering fish eggs and other aquatic organisms.  This sedimentation process alters the geology and diversity of the aquatic ecosystem and degrades viable habitat for aquatic organisms.  Both the nutria and the feral pig contribute to these and other problems, and thus we need to learn from the choices of our past and not continue to repeat them.

Educate Others

Feral swine and nutria are now well-established and, though we wish we could turn back the hands of time, we cannot and thus must live with our choices.  However, the choices of tomorrow do not have to mirror the choices of our past.  It is important as fisheries professionals that we educate the public about the consequences of introducing non-native species into aquatic ecosystems.  It is imperative that we take the time to visit schools, speak to civic groups, utilize social media and other outreach platforms, and share with this generation and the next the importance of understanding the negative impacts our native species will endure should we choose to continue introducing ANS in our state and beyond.  How many of us have reached out to our own family members or friends and shared our knowledge and expertise?    Knowledge is power…spread the word…stop the ignorance!