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.
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.
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!