The invasive snakehead fish, which is native to Africa, Asia, Indonesia, and Malaysia, has been found in nine states in the United States and has notably developed a reproducing population in South Florida, Maryland, and Hawaii. This case study discusses the environmental impact and policies surrounding the snakehead fish population in the United States’ waters, as well as three other fishes (smallmouth bass, largemouth bass, and trout) that are native to some bodies of water in the United States, but non-native to others. This case study will examine the paradox that exists when the support of anglers and/or other important stakeholders in wildlife management does not match the potential a species has to damage a native habitat. Readers should be able to think critically about how people have come to define what is seemingly good for the environment based on personal human interest rather than environmental interest. They should also think about how easily the environment can be changed, even permanently, due to small cases of invasive species spreading rapidly from human practices.

KEY MESSAGE

This case study analyzes the problem of invasive snakeheads found in the Southern Florida Canals and Potomac River. It also discusses the relationships between the public and other known non-native and invasive fish species in the eastern United States. Students should be able to think critically about how people have come to define what is seemingly good for the environment based on personal human interest rather than environmental interest. Students should also think about how easily the environment can be changed, even permanently, due to small cases of invasive species spreading rapidly from human practices. While reading, think about what truly native North America may have been like in comparison to its current state. Also, question the purpose of management practices used for aquatic environments that have changed substantially over time.

INTRODUCTION

Snakeheads (Figure 1) are aggressive air-breathing predatory fish with teeth that can devastate their prey [1]. They have an elongated body with long dorsal and ventral fins for speed in the water while also having the ability to slither short distances on land. Of the 29 recognized snakehead species coming from Africa, Asia, Malaysia, and Indonesia, 2 particular species of snakehead concern the state game commissions and biologists in Florida (Channa marulius, the bullseye snakehead) and Maryland (Channa argus, the northern snakehead) [1]. Both states have declared snakeheads an invasive species and made it illegal for anglers to release any live snakeheads back into the water.

Figure 1.

Snakehead (Channa striata). Photograph by Wibowo Djatmiko, CC BY-SA 3.0.

Figure 1.

Snakehead (Channa striata). Photograph by Wibowo Djatmiko, CC BY-SA 3.0.

There is an immense amount of controversy within the fishing community surrounding the snakehead’s current and future effects on the ecosystems it invades and will likely invade. With a warming climate, it is possible that the established range of both the warm water bullseye snakehead and the cold water northern snakehead could spread further northward. The publicity surrounding the snakehead’s status as an invasive species raises interesting questions about differences between environmental health impacts and human-perceived impacts, as well as how disputes can emerge between the public, anglers, and government officials over the acceptability of invasive species.

CASE EXAMINATION

This case study examination of the snakehead will also introduce important concepts like the distinctions between native, non-native, and invasive species, as well as the role of federal and state law in controlling non-native species.

Bullseye and Northern Snakehead Invasion

The first report of snakeheads in the United States came from Silverwood Lake, California in 1997, where a single fish was found [2]. Following the first report, two fishes were caught in the St. Johns River (Florida) in the early 2000s and then again in Lake Michigan, Maryland, Massachusetts, and New York. They can be found throughout the United States, but established northern snakehead populations are found in Maryland, Virginia, Pennsylvania, New York, Florida, and North Carolina [3]. It is possible that habitats as far north as the Hudson Bay could be favorable to snakeheads [4].

The northern snakehead is very aggressive in its strength and nature and is native to the Yangtze River in China. The first reproducing population was found in a pond in Maryland in 2002. While those snakeheads were subsequently eradicated, northern snakeheads were later found in the Potomac River, having been introduced as early as 1998 [5]. The northern snakehead has been projected to spread to the entire Chesapeake Bay sub-watershed within 52 years, thus it has a high invasive potential [6]. Snakeheads are able to survive up to 4 days outside the water and reproduce twice a year in May and August. During this period, male snakeheads create circular nests in shallow aquatic vegetation and sexually mature snakeheads are seen jumping on the surface of the water [7]. The snakehead can consume prey as large as one-third of their body weight, which shows how easily they can take over an ecosystem and threaten native fishes, crustaceans, or amphibians [3]. Northern snakeheads consume mostly larger fish in their diet, which is similar to the bass that live in the same waters [5].

Native, Non-native, and Invasive Species

When determining whether a species is native or non-native, one must first consider the geographical and temporal context. In terms of geography, the most basic unit of analysis is a specific body of water or watershed, such as the Chesapeake Bay. But other potential boundaries include municipal, state, and national borders. In fact, governmental entities at each level regulate non-native species, but their scope of concern is different. The U.S. federal government is concerned with preventing the movement of non-native species across the country’s borders, as well as interstate transport. States, however, are primarily concerned with the species crossing their borders and affecting their specific bodies of water and watersheds. This means that species native to some parts of the United States, and thus not considered invasive or injurious by the federal government, can be non-native and quite damaging in other states. The striped bass, for example, is native to the East Coast of the United States, but non-native in California, where it was introduced in 1879. Thus, it is necessary to consider both federal and state law when understanding the regulation of invasive species.

Species are typically defined using the following three terms:

  1. Native: A species historically existing in an ecosystem of interest.

  2. Non-native: A species that is not historically native in an ecosystem of interest.

  3. Invasive: A species that is not historically native to the ecosystem of interest, has the potential to colonize new environments, and puts at risk the native plant or animal populations, as well as the commercial and recreational qualities of the ecosystem [8, 9].

Traditionally, biologists, botanists, and zoologists use the terms native and non-native to describe a species’ historical presence in a habitat. In 1958, the term invasive was applied to non-native species and took on a decidedly militant and negative framing [10]. The term invasive implies that there is damage occurring to the local ecosystem. Granted, some species are more likely to be invasive than others [11]. Thus, species are strictly speaking either native or non-native, given the geographical and historical context, but some non-native species are further considered harmful and invasive. It is notable that there is disagreement among biologists as to whether non-native species should be automatically considered dangerous to a habitat [12]. Some argue that this can only be determined based on the species’ effects, as some species have positive effects on non-native ecosystems [12]. In fact, some non-native species are introduced to help control invasive species (called biological control) [13]. The federal government and each state play important roles in regulating non-native fish species.

Federal and State Regulations

The Lacey Act (18 U.S. Code 42) was passed by Congress in 1900 and deems it unlawful to import, transport across state lines, or sell in the United States or land possessions of the United States any species deemed injurious, unless permits are granted by the U.S. Fish and Wildlife Service [14]. The northern snakehead was deemed injurious under the Lacey Act in 2002, after its discovery in a Maryland pond [1]. There is a formal process for deeming a species injurious, thus not all non-native species are designated as such by federal law. The Act is enforced by the Department of the Interior’s Fish and Wildlife Service. President Clinton sought to augment efforts to combat invasive species through a 1999 Executive Order (No. 13112, 64 C.F.R. 6183) that defined non-native species as invasive when they damaged the environment or economy. The Order also created the National Invasive Species Council and called for additional executive departments and agencies to aid in the prevention of invasive species.

The states are key actors in setting rules for catch and release of non-native and invasive fish. For example, it is illegal to possess a live snakehead in Maryland, Pennsylvania, and Virginia. Anglers should kill any caught snakeheads and report if a tagged fish was caught and killed. Possession of live snakeheads in Florida is a misdemeanor and can come with a US$500 fine and/or 60 days in jail. In Pennsylvania, anglers violating state law can have their fishing and boating privileges revoked for a first offense and can be fined US$200 for a second offense. Thus, understanding the landscape of invasive species management requires knowledge of varying state rules.

Informal Actors

Other informal actors also play a role in setting the government’s invasive species agenda and establishing policy [15]. For example, anglers increase their voice when bonded together in fishing clubs and organizations. The Yellow Breeches Anglers and Conservation Association, for example, is a trout hatchery administered by a club of anglers located along the Yellow Breeches Creek in Pennsylvania. The group stocks hatchery-raised trout to maintain a productive trout fishery for local anglers. If an invasive fish, such as the snakehead, were to get into the Susquehanna River, they could potentially spread to the Yellow Breeches Creek. The possible devastation that snakeheads could cause to the quality of the Yellow Breeches Creek trout fishery would likely mobilize these anglers to press for solutions to the problem. Advocacy by such a coalition could then lead to action by the state [16].

Media coverage can be beneficial for bringing attention to invasive species, such as the snakehead. However, the media could also create misconceptions about the species’ degree of danger to the local ecosystem. If people see no serious changes in the ecosystem the snakeheads inhabit, environmental skepticism could develop within the local community [17]. In Asia, these fishes are seen as a delicacy [18]. Not only are they popular in Asian cuisine but also snakeheads are now being served in both Maryland and Virginia as an exotic food item [18]. Some chefs in Maryland have become creative in deep frying the fish and serving them as snakehead nuggets [18]. Greater assimilation in the local culture and economy could increase support for a species over time.

Stakeholder Perceptions

Thus, there can be important differences in perceptions of the dangers of a non-native species between the public, anglers, and conservation officials. Furthermore, angler’s support for non-native species does not always coincide with the health of the ecosystem. One research team in the United Kingdom surveyed conservation managers, anglers, and the public regarding their perceptions of threat from five non-native species (grey squirrel, Japanese knotweed, harlequin ladybird, signal crayfish, and topmouth gudgeon). The public rated the most visible—but actually least dangerous to habitat—grey squirrel as most concerning, whereas the most dangerous to habitat, the topmouth gudgeon (a parasite carrying fish), was rated the least concerning. In general, the public was far less aware of the concerns regarding aquatic invasive species (i.e., the crayfish and gudgeon) than terrestrial. Anglers were more aware of species, such as the gudgeon, that threatened their activities, though they still rated them as less concerning than conservation managers. Even conservation managers, however, rated the gudgeon as least concerning, even though it is more damaging to native habitats than the other four. According to the authors, it was media and Parliamentary pressure that fostered management action of aquatic species, not conservation managers.

Another example comes from the striped bass in California. Originally introduced for commercial fishing, overfishing led to a ban on that practice, but the fish subsequently grew in popularity among sport anglers. This support grew to the point that there are now concerns about declines in the bass population [19]. Nevertheless, the striped bass has threatened native fish, such as the Chinook salmon and longfin smelt. Due to the sport fishing popularity of the bass, however, the California Department of Fish and Game undertook a program in 1996 to substantially increase the size of the bass population. As the effects of the bass on native threatened species drew more attention, particularly of agricultural interests, associations representing anglers and businesses pushed back against more recent state attempts to limit the bass population [20].

Survey-based evidence demonstrates that anglers support for native versus invasive species is highly context-dependent [2123]. The introduction of striped bass in Tennessee (for the purpose of controlling gizzard shad) produced a rift among anglers, with some decrying the decline in native populations of walleye, crappie, and black bass while others enjoy catching large striped bass [22]. These examples illustrate the fact that there are multiple stakeholders in state regulations of non-native species, and regulators must consider not only the environmental and economic dimensions of non-native species but also the human/social dimension. Each is important to evaluate when managing non-native species [24]. A lack of awareness or concern among stakeholders, particularly anglers and conservation managers, undermines the effectiveness of invasive species management.

Angler Opinions of Snakehead Fishing

To our knowledge, there have been no systematic studies of angler opinions regarding the snakehead. Yet, in spite of the plentiful information available regarding the invasiveness of snakeheads and the procedure for catching and killing, arguments in support of snakeheads as game fish are emerging. A Washington Post opinion column in July 2018 argued that the log of fish catches maintained by the Maryland Department of Natural Resources is proof that anglers find the snakehead desirable. In fact, the author lamented the decline of snakehead populations in the Potomac due to Maryland and Virginia’s catch and kills policies. There is novelty to a fish that can spring “a foot in the air” and “scatter” anglers [25]. In addition, the snakehead are known for not only being “fun to catch” but also “delicious” [26]. This is not evidence of widespread angler support for the snakehead in Maryland and Northern Virginia, as a systematic study of opinion is required. Yet, it illustrates an emerging argument in support of the fish due to the excitement of catching them. Even if the snakehead population is declining, it is possible that increasing support among some key stakeholders, such as anglers and their organizations, could undercut enforcement of species control policies. This point is perhaps best illustrated by additional cases of interbasin fish transfers that occurred in the past within the United States and have proven difficult to reverse in recent decades.

INTERBASIN TRANSFERS OVER TIME

As briefly mentioned above with the striped bass, there are times when fishes native to North America are purposefully transplanted to a non-native body of water for the purpose of sport fishing, commercial fishing, or biological control of an invasive species. The Lacey Act does not apply in these cases. Instead, states have the sole responsibility for managing such transfers. Alas, such fish may have a similar negative impact on local habitats as species transferred across national borders. In the long-run, some introductions lose favor with key stakeholders, while others do not. The striped bass in California has become a prized sport fish, for which sport fishing groups are fighting to protect, whereas local anglers in Tennessee have fought against the striped bass and its impact on local native fish.

Largemouth Bass

The largemouth bass (Figure 2), originally native to only certain parts of the United States, has been widely stocked across the country for the purpose of freshwater sport fishing. The largemouth bass is detrimental to certain small native minnow and fish species populations through noticeable population decline and sometimes extinction in small fish species [27]. Both the largemouth bass and northern snakehead are arguably as harmful to the health of the Potomac River’s ecosystem due to their similar aggressive predatory eating habits. However, the snakehead is foreign in the eyes of local anglers and biologists with its sharp teeth, strange snake-like appearance, and air-breathing abilities, whereas the largemouth bass is familiar to the public and a popular game fish species. At this time, the public familiarity and economic and recreational benefits of the largemouth bass make the largemouth a more acceptable species in the Potomac River.

Figure 2.

Largemouth bass. Photograph was taken by Hans Shollenberger.

Figure 2.

Largemouth bass. Photograph was taken by Hans Shollenberger.

Smallmouth Bass

Smallmouth bass (Figure 3) are predatory fish originally transported from the native range in the Great Lakes and Mississippi River basin to the Susquehanna River and surrounding Chesapeake Bay region for sport fishing in the 1850s [28]. Smallmouth bass have become such an important part of the Susquehanna River that its population numbers are currently used to gauge the River’s health and water quality [28]. Healthy smallmouth bass can be used as an indicator of water quality due to its low tolerance to pollution, but on the other hand, it is a carnivorous generalist fish that feeds on many different aquatic animals. This disrupts the network among native aquatic life. Thus, do healthy bass populations necessarily correlate with a healthy environment and river ecosystem? Using the smallmouth bass as the top health indicator of the Susquehanna River rather than assessing other health factors, such as native underwater plant life, frog population numbers, shoreline health, and more, could be seen as a predominantly economic view of the River’s health.

Figure 3.

Smallmouth bass. Photograph was taken by Hans Shollenberger.

Figure 3.

Smallmouth bass. Photograph was taken by Hans Shollenberger.

Smallmouth bass yields an estimated US$630 million in annual sales in Maryland, Pennsylvania, Virginia, and West Virginia [28]. Smallmouth bass is favored by anglers and protected during spawning times due to recent declines in young-of-the-year bass numbers. With the positive economic ties and recreational opportunities for local anglers, it is clear why the smallmouth bass is an accepted non-native in the Susquehanna River. The question remains whether the smallmouth bass was actually beneficial to the environment after its introduction in the 1850s. Did the economic interests of the time overlook the importance of the environmental health of the Susquehanna River? Human settlement and the introduction of non-native species have undoubtedly changed the local ecosystems, and thus it can be difficult to determine the full environmental impact of introducing smallmouth bass into the Susquehanna River.

Brook Trout

The brook trout (Figure 4) is Pennsylvania’s official state fish and the Commonwealth boasts the best trout fishing in the world, but native brook trout have been crowded by introductions (including annual stocking) of (collectively) more popular brown and rainbow trout. Among the effects of acid mine drainage, agriculture, deforestation, and other invasive species, non-native trout are part of the story of brook trout declines in over 70% of their native waters in the state [29]. Brown and rainbow trout were initially introduced to counteract declining brook trout populations, though they also compete in some streams [30]. In a 2008 survey of anglers by the Pennsylvania Fish and Boat Commission, only 20% of 1,562 respondents preferred fishing for the native brook trout [31]. While a total of 46% preferred either the rainbow or brown and 34% had no preference (Figure 5).

Figure 4.

Brook trout. Photograph was taken by Hans Shollenberger.

Figure 4.

Brook trout. Photograph was taken by Hans Shollenberger.

Figure 5.

Angler preference for trout types in 2008 Pennsylvania Trout Fishing Survey [31].

Figure 5.

Angler preference for trout types in 2008 Pennsylvania Trout Fishing Survey [31].

CONCLUSION

This case study was meant to stimulate discussion on the topic of non-native fish species, by initially looking at the northern snakehead, which migrated internationally, as well as other fish species that were transferred within the United States. Many of the interbasin transfers were for sport or commercial fishing and had broad support at the time of their transfer, whereas the snakehead was not intentionally introduced as beneficial. Stakeholder support for some non-native species fluctuates over time. One main take away is how perceptions of different stakeholders (the public, anglers, industry, and government) shapes the acceptability and management of non-native species. Economic and recreational benefits can and have outweighed environmental health in several of the fish discussed above. The clearest example being the smallmouth bass in the Susquehanna River, whose introduction over 150 years ago and popularity among anglers has made it a marker of health in an ecosystem to which it is not native.

It must be mentioned that invasive species do not have to be large fish or mammals to be harmful to the environment. Invasive bacteria, fungi, and insects can also harm foreign ecosystems. The cases of mile-a-minute weed, emerald ash borers, gypsy moths, lantern flies, Dutch elm disease, and many more in Pennsylvania illustrate the large and growing threat of invasive species. There are two primary modes of addressing invasive species through policy: (1) by targeting pathways of transfer from other ecosystems or (2) by targeting specific species [32]. While it is important to enforce both policy practices for invasive species management, invasive fish species cases tend to be uncontrollable once a population is established. Once a fish species is noticed in a river system, it is challenging to succeed in eradication of that species from the waterway. The solution to prevent the establishment and spread of invasive species requires the efforts and acceptance of multiple stakeholders. It also requires the dissemination of information regarding the ways in which invasive species endanger local habitats and how established invasive populations can be controlled.

CASE STUDY QUESTIONS

This case study can either be discussed as a whole or in two different parts. We suggest using the whole case, if time permits, but then choosing questions that are most directly relevant to the instructor’s lesson goals. For instance, if the focus is how conflicting preferences affect species management policy, questions 1, 3, and 4 are particularly relevant. If the focus is the impact of species management on the environment, questions 2, 3, and 6 are most relevant. If only focusing on intercontinental invasive species, without discussing interbasin transfer decisions, questions 2 through 5 are relevant. The whole case, however, gives students a more comprehensive picture of the complexities of non-native species policy.

Entire Case

  • 1.

    What major factors affect the public’s perception of what is an acceptable non-native species versus an unacceptable invasive species that needs to be eradicated? (Hint: Think of the largemouth bass and northern snakehead in the Potomac River. Both fish potentially affect the ecosystem in similar predatory ways.) How does public opinion and economics weigh in on this?

  • 2.

    How are human morals and the safety of the environment at play in the choosing of which species to accept and which to attempt eradication?

International Transfer (Snakehead)

  • 3.

    Consider the environmental, economic, and social aspects of species management. What kinds of information are necessary for weighing the costs and benefits of managing a non-native/invasive species? How should governments weigh scientific, economic, and public opinion data? How can differing stakeholder views be balanced in a way that enhances the health of local ecosystems?

  • 4.

    In terms of value, snakeheads are fun to catch and good to eat (considered a delicacy in Asia). Do these mentioned benefits of the snakehead to local anglers and the community outweigh the possible negative effects on native species and the environment? Think economically as well as environmentally and argue both sides.

  • 5.

    As mentioned, some anglers are starting to promote the excitement of catching snakeheads, as well as the tastiness of their meat. Do you think the game commissions of Virginia and Maryland will continue to require the killing of any snakeheads caught in the Potomac or will they accept it as here to stay and remove the unlawfulness of catch and release? What factors might change their minds? How do you think each decision would affect the impacted ecosystem and public view of the species in the long term?

Interbasin Transfer

  • 6.

    Think about and discuss what an untouched North America looked like before serious human intervention. For example, think about the abundance of brook trout in Pennsylvania before widespread deforestation, agricultural and industrial runoff, and river damming. Brown and rainbow trout were introduced to counteract native brook trout declines. Both are now widely accepted fish among anglers, but they do compete with native brook trout in some streams. Discuss how environmental management may change over time with the changing idea of what is considered environmentally healthy due to human-driven changes in local ecosystems.

AUTHOR CONTRIBUTIONS

Conceptualization—HS, ED, DJM. Investigation—HS, ED. Project administration—HS, ED. Supervision—DJM. Visualization—HS, ED. Writing—original draft—HS, ED. Writing—review and editing—HS, ED, DJM.

FUNDING

No funding was used for this case study.

COMPETING INTERESTS

No competing interests existed for this case study.

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