Implications and Potential Solutions
Invasion of the Round Goby
New York’s Waterways
Patrick McLaughlin and Monica Phillips
St. Lawrence University
Professor: Dr. Erika Barthelmess
29 April 2005
Table of Contents
Why is the Round Goby a successful invader?
Identification of Stakeholders
Description and Feasibility of Solutions
Interruption of Courtship Behavior
Manipulation of Nest Sites
Description and Feasibility of Best Solutions
Ease of Implementation of Best Solutions
Step-by-Step Implementation Plan
The Round Goby (Neogobius melanostomus) is an aquatic invasive species that invaded North America from Europe approximately 15 years ago. Since then the species range has grown to include all the Great Lakes and parts of the St. Lawrence Seaway, though official documentation has not yet recorded its actual range. The species was most likely brought here the same way many other aquatic species entered the Great Lakes, which is through the ballast water of transoceanic ships. Ballast water regulations are just now being permanently and universally regulated after identification of their incredible threat and already huge cost to the environment.
The round goby affects aquatic ecosystems in a variety of ways. It is a smaller fish that eats mainly mollusks and fish eggs, though studies have shown it to be aggressive in eating anything it can get its mouth around. Interestingly enough, its main food source comes in the form of another well established invasive species, the zebra mussel. The goby is changing the population dynamics of many species in ways which we do not yet understand, but continued research aims to predict and prevent its negative impact.
The round goby is a perfect example of a successful invasive species and poses many challenges in terms of management options. Our purpose was to develop potential solutions to the problems posed by the goby invasion, however we found most solutions were not adequate in solving the problems to our fullest desires. In the end we realized that there is no silver-bullet cure to invasive species, and eradication is not realistic. Only through community education and potential population managing techniques can we hope to stop the further spread of the round goby and limit its already negative effects upon our economy, environment, and human well-being.
To fully understand the problems associated with the Round goby (Neogobius melanostomus) we must first explore the concept of an invasive species. Invasive species are defined by the U.S. Congress as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health” (National Agricultural Library, 2005). Furthermore, “alien species” is used as a term within this definition, and Congress went on to define this as: “…with respect to a particular ecosystem, any species, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem” (National Agricultural Library, 2005). In other words, invasive species are organisms that have somehow established themselves in an ecosystem to which they are not native. The results of such an introduction could cause economic, environmental, or human-health problems due to the fact that this species will somehow disrupt the processes, relationships, and balances that exist in the invaded ecosystem.
Despite Congress’s distinct definitions, invasive species are also commonly referred to as alien species or exotic species. The definition set forth by Congress also does not fully explore some major characteristics about invasive species. Specifically, in regard to how such a species enters an ecosystem, there is distinct terminology used to explain how a species becomes invasive:
Imported- This terms actually refers to the act of a species being transported (either through natural or anthropogenic means) outside of its native range.
Introduced- This is the actual release or exposure of the species into the new ecosystem that it has been imported into.
Established- The introduced species becomes established when it finds a way to occupy a niche in the new ecosystem such that it is able to reproduce and maintain its persistent existence.
Pest- This is an essential part of the overall definition, because it refers to the ability or tendency of an established species to become a nuisance. “Nuisance” denotes the species is causing economic problems, environmental degradation, or harm to human health, which is a vital characteristic for it to be considered a true invasive species.
As a general rule, invasive species follow a pattern of invasion in reference to these terms. The “10% Rule” says that of all the imported organisms only 10% are actually introduced, and of those introduced only 10% become established, and only 10% of the established species become pests. In other words, most of the initial importations of species do not result in the creation of an invasive species because they simply fail to satisfy one of these components. Obviously other factors may affect the success rate of invaders, such as how many and how often a specific species is introduced, collectively referred to as invasion pressure (Barthelmess, 2005).
There are also certain characteristics of the potential invader species that improve its chances of becoming an established pest. Many of these characteristics have to do with the life-history traits of the species, and the characteristics are seen in many of the most famous invaders whether they are plants or animals, terrestrial or aquatic. Possibly the most important to establishing itself is the tendency for a good invader to have a high reproductive rate and a short generation time (i.e.- hits sexual maturity quickly). Complimenting this would be the trait of a long life span, such that each individual persists and reproduces many times. To successfully invade you must “conquer” the new ecosystem, so have high dispersal rates is crucial. Habitat generalists, or those who can survive in a variety of different environments, usually succeed, as do those species that are tolerant of a wide range of varying conditions (this trait is specifically important to the round goby success). Lastly, as the title “invader” implies, those that are successful also tend to be aggressive in one form or another (Barthelmess, 2005). Invasive species have become a huge problem due to the fact that because the successful ones have these characteristics, they are very hard if not impossible to eliminate after they have become established. In fact, invasive species are the second greatest threat to native species and thus biodiversity after habitat loss (National Agricultural Library, 2005).
There are countless invasive aquatic species in North American. The Great Lakes alone contain 162 invasive species (“Sea Grant”). Three well know examples of aquatic invasive species include: Zebra mussels (Dreissena polymorpha), Eurasian Watermilfoil (Myriophyllium spicatum), and the sea lamprey (Petromyzon Marinus).
Zebra mussels are native to the Black and Caspian Seas in Eastern Europe. They were transported across the Atlantic Ocean in the ballast water of an empty cargo ship. This zebra mussel was first sighted in the Great Lakes in the mid-1980’s and is now prevalent in the water systems of North America. The zebra mussel has completely changed the habitats that it invaded because it has increased the water clarity and the sunlight penetration. They colonize on docks, boat hulls, water intake pipes and valves. Their only known predators in North America are diving ducks, carp, and sturgeon. These few species do not ingest enough zebra mussels to manage the zebra mussel population (“Sea Grant”).
Eurasian watermilfoil is an invasive aquatic plant that is native to Europe. This plant invaded North American in the 1940’s. Today, it can be found in 45 of the lower United States and Canada. It has pushed out native plants, clogs boat propellers and degrades the shoreline. It does not seem to have any negative effects on the native flora of the ecosystems. Management techniques such as chemical, physical and biological have all been attempted to control Eurasian watermilfoil (“Sea Grant”).
The sea lamprey in another invasive fish species located in the Great Lakes. The first sighting of this parasitic fish was in 1846, and by 1946 there were successful reproducing population in all five of the Great Lakes. The sea lamprey had a huge negative impact on the predator/prey relationships between the native flora and fauna. Extensive management techniques have been used to decline the populations of the sea lamprey. These efforts have been successful however; they will need to be continually monitored so their populations do not get out of hand again (“Sea Grant”).
The round goby is an aquatic invasive species in North America, an obvious assumption based upon the fact that it is a fish. What is not so obvious is that the methods for importation, or vectors, for aquatic invasive species differ from those of terrestrial invaders. What is unique to aquatic invaders is that the vector usually must be one that somehow encompasses an aquatic habitat for the organism or its propagules throughout the journey from its native range to the new ecosystem. Terrestrial animals can generally survive such a journey as long as they have air to breath, and plants are even easier to transport in terms of seeds. However, aquatic organisms need water and the conditions of that water (temperature, salinity, oxygen content, etc.) must be within a tolerable range. This severely limits the potential vectors in comparison with terrestrial organisms, because it involves the actual transport of a small body of water along with the organism.
The main vector for aquatic invasive species has been found to be inside the ballast water of transoceanic tanker ships. Ballast water is water the ship pumps into its hull for stability and safety during the journey across an ocean. Once the ship enters a port or inland waterway, ballast water is no longer needed for stability and no longer desired as it requires more energy to power a ship weighted down by a large mass of ballast water. Thus, ballast water is pumped into a ship at the port of origin and pumped back out of the ship once it reaches the destination. All sorts of aquatic plants, seeds, larvae, eggs, and organisms can be sucked into a ship via the ballast water and survive the journey only to be spewed out into a new environment. Since the discovery of this vector of introduction there has been much debate as to how to regulate ballast water emissions (BWE) and more importantly how to enforce it. Proper ballast water management takes more time, which equals money, and thus many ship captains are reluctant to agree to voluntary regulations. The introduction of the round goby to North American waterways has been traced back to probable ballast water emissions along the St. Clair River which connects Lake Erie and Lake Huron (Figure 1).
Figure 1. Map of most probable locations for invasive species introductions via ballast water emissions in the Great Lakes waterways (Adapted from: Cangelosi, 2004).
We define an “internal vector” as a method of transport for an invasive species within the ecosystem it has already entered. Many times the spread of an invasive species is facilitated by the actions of humans in that region. Small fish such as minnows are often used by anglers for bait, and thus we have identified the most probable internal vector for the round goby as being through bait-bucket “emissions.” Many times anglers use live bait such as small fish, and may dump the remnants of the bait into the water body they are fishing after the day’s fishing is through. Unfortunately, the remaining live bait may not be native to the water body even if it is native to a nearby water body that the fisherman or the bait shop gathered it from. If gobies are gathered as bait in one area, and released as someone’s bait-bucket emissions in a new area, they can successfully disperse to new regions. To counteract this, fishing regulations such as those in New York State prohibit the use of the round goby as bait and attempt to remind anglers of the proper way to dispose of their bait-bucket emissions.
The round goby originates from the Black and Caspian Seas which are located in Eastern Europe (Charlebois et al. 1997, Figure 2). The goby expanded its range to the Sea of Marmara, tributaries of the Black and Caspian seas (Charlebois et al. 1997).
Figure 2. This image denotes the range of the round goby in Eastern European seas. This information was from October 1996 (Charlebois et al. 1997).
In the late 1980’s the round goby was transported from its native hemisphere to North America (Vanderploeg 2002). They were carried across the Atlantic in the ballast water of a tanker ship traveling from the Caspian Sea (Charlesbois et al. 2001). The first documented traces of this invasive species did not occur until June 28, 1990, when an angler caught a round goby in the St. Clair River (Charlebois et al. 1997) which connects the great lakes; Huron and Erie. By 1996, the goby had expanded its range from the western shores of Lake Superior to the eastern shores of Lake Ontario (Charlesbois et al. 1997, Figure 3). Unfortunately, the round goby’s success does not end in the Great Lakes.
In 2003, a study was completed in Pennsylvania tributary streams of Lake Erie to determine the status of the Round Goby (Phillips et al.) Six streams were sampled and four of those streams (Elk Creek, Walnut Creek, Twentymile Creek, and Sixteenmile Creek) contained round gobies (Phillips et al. 2003). Elk Creek showed the most extensive colonization of round gobies. Of the total number of fish present in the creek 17.1% were round gobies (Phillips et al. 2003).
During the summer of 2004, the round goby was sighted of the shores of Waddington, NY in the St. Lawrence River (pers. comm. Woodward). There are also regular sightings of the round goby reported to the New York State Department of Environmental Conservation every year (pers. comm. Carlson). Fortunately, there are presently no reported sightings of the round goby in the St. Lawrence River Watersheds (pers. comm. Carlson). This doesn’t necessarily mean they haven’t invaded these water systems yet, they just have not been consciously reported to the New York State Department of Environmental Conservation (NYS DEC).
Figure 3. This map displays round goby sightings in North America’s Great Lakes (“Sea Grant”).
The round goby has many unique characteristics that enable us to correctly identify this invasive fish. The goby is a small, soft bodied fish. They can grow to 250mm as adults and they are gray with blotches of black and brown. They are benthic, bottom dwelling, fish that perch on rocks and other substrate (Marsden 2003). The round goby is known for their large heads and large-round eyes (Figure 4). Their dorsal fins lack spines and there is a distinct large black spot on the front dorsal fin (Figure 4 & 6). An exclusive feature that the goby presents is fused pelvic fin (Marsden 2003). All native fish display two pelvic fins (Figure 5). These fins are used to create a suction disk on the ventral surface of the goby. The suction disk is used to stabilize the goby in waterways that have a stronger current or if there is an unexpected disturbance in the flow of water (Charlesbois et al. 1997).
Figure 4. Round Goby in the palm of a human hand (“Sea Grant”).
Figure 5. Comparison of two fish: the sculpin and the round goby (Charlesbois et al. 1997).
Figure 6. Diagram of distinguishing features for the round goby. This image was taken from a Round Goby Watch card (Sea Grant 1998).
Research conducted upon the round goby population in North America has found that they differ slightly from the population in their home range. Specifically, sexual maturity is reached at a younger age for round gobies in North America when compared to their European counterparts. In North America, females reach sexual maturity at 1-2 years, and males at 2-3 years (Corkum et al., 1998). Additionally, they may spawn up to five times during the year due to geographical and temperature differences as compared to Europe (Vanderploeg et al., 2002). During spawning, these fish may use chemical, acoustic, and visual communication to locate and attract potential partners. The larger gobies will also “push” the smaller gobies away from the optimal breeding areas, thus forcing mate selection of females with the largest, strongest males who have established a prime nest site. Nest sites are usually in rocky habitats, or near any type of shelter such as submerged logs and debris. After females have deposited their eggs in the nest, the male will aggressively guard the eggs from predation by other fish as well as cannibalism by other gobies. Egg clutches within one nest maybe be composed of eggs from up to 6 different females, all fertilized by the same male nest owner. An egg clutch for a nest that has received contributions from 4-6 females may be in the range of 8-10,000 in number. Fertilization rates for males have been recorded at 95%, and hatching success has also been recorded at 95% due to intense guarding of the nest by the male. During the larval maturation period, the males are so intent on guarding their nest that they will often times not feed. Thus many studies have asserted that it may be common for males to die after one spawning period due to this self-induced starvation, though more research needs to be done to verify this potentially widespread occurrence. The life span of gobies in North America has been verified as being up to 7-8 years, though average for gobies in Europe is around 4 years (Corkum et al., 1998). Round gobies also seem to prefer littoral areas with large cobbles or cavities. Depending on the body of water the goby may inhabit depths up to 30m deep (Charlebois et al., 1997).
Why is the Round Goby a Successful Invader?
Round gobies display several of the characteristics that determine whether or not an exotic species will become successive in its new habitat. The round goby proves to have a high reproductive and dispersal rates and they are considered habitat generalists. The goby is a habitat generalist because of its wide ranging diet, water temperature tolerance, salinity tolerance and their ability to withstand high flow rates and low oxygen concentrations.
The goby is considered to have a high reproductive rate because they are multiple spawners and have the ability to spawn six times in a single year (Vanderploeg et al. 2002). The goby can spawn in water that ranges between 9-26˚C in temperature (Corkum et al. 1998). However, in the Detroit River gobies reproduce in between the months of April to August and usually spawn three times (Corkum et al. 1998). Females have the ability to lay anywhere from 300-5000 eggs in a single spawning period (Charlesbois et al. 1997) whereas a study conducted in the Detroit River observed females laying 84-606 eggs (Corkum et al. 1998). The round goby also has successful fertilization rates and hatch rates of up to 95% (Charlebois et al. 1997).
The high dispersal rates of this invasive fish are both intraspecific and interspecific. The aggressive behavior of gobies has facilitated the dominance of optimal nesting sites. The round goby has been successful in pushing out native fish from nesting sites (French and Jude 2001). This allows gobies to be more successful reproductively than native fish occupying the same niche. An intraspecific behavior that increases the goby’s dispersal rate is when larger gobies displace smaller gobies out of the optimal, rocky, habitat into a more sandy area. The smaller gobies are then forced to find more suitable habitat that is not already inhabited by larger gobies. This in turn expands their range and leads to more interspecific competition among other native fish occupying the optimal habitat (Corkum et al. 1998).
As habitat generalists the round goby has the ability to survive in a wide range of ecosystems. The goby’s diet encompasses a wide range of aquatic organisms. Their diet consists of crustaceans and mollusks (zebra mussels), polychaetes, small fish, goby eggs, chironomid larvae (Charlebois et al. 1997), amphipods, cladocerans, crayfish, dragonflies, dreissenids, isopods, and mayflies (Corkum 2004). Studies of the round goby’s diet showed that 78% of their diet consisted of mollusks (Charlebois et al. 1997). They also prefer to ingest zebra mussels to any other mollusk (Ghedotti et al. 1995). This may relate to the fact that both species are originally from the Black and Caspian Seas and are therefore natural linked on the food chain.
The round goby thrives in water temperatures that range from -1 to +30˚C, and is therefore considered eurythermal (Charlebois et al. 1997). Eurythermal refers to animals that have the ability to tolerate large range of temperature (Webster Dictionary). Gobies will leave areas in which dissolved oxygen is less than 50-60% of saturation. Their threshold oxygen concentration ranges from 0.3-0.9 ml/L which comparatively low. This fish tolerates a flow rate of 0.34 m/s for 3-4 min and at faster flow rates they use their pelvic fins to brace against the current (Charlebois et al., 1997). Gobies are able to reproduce in fresh and saline water and embryonic development proceeds normally at salinities of 4.2-19.5% (Charlebois et al., 1997).
The Great Lakes and the St. Lawrence Seaway are at a high risk of invasion by aquatic invaders due to the major shipping routes along these waterways. Invasive species cause complex food webs to be dramatically restructured which can lead to changes in energy flow through trophic levels. Round gobies have an intense competition with mottled sculpin and threaten to cause their local extinction which can drastically impact the benthic invertebrate community structure. Nearly every fish species relies on this community at some point during its life cycle, and thus a dramatic change can have implications for all fish and the economically important fisheries via alteration of fish population dynamics (Berg & Janssen, 2002).
There are five smaller native fish that are being affected by the successful invasion of the round goby. These fish include: the mottled sculpin (Cottus bairidi), johnny darter (Etheostoma nigrum), brindled madtom (Noturus miurus), logperch (Percina caprodes) and the northern madtom (Noturus stigmosus). Gobies have had significant impacts upon the densities of mottled sculpin (Cottus bairdi) and logperch (Percina caprodes). Gobies interact negatively with the sculpin in two ways: aggressive competition forces the sculpin into deeper habitats where they are more susceptible to larger predators, and the goby has also been shown to interfere with sculpin spawning resulting in a loss of recruitment (Corkum, 2004). All of these fish are being out competed by the round goby for nest sites and food. However, the mottled sculpin has shown the greatest decline because the sculpin and the goby occupy very similar niches (French and Jude 2001). The round goby is also much more aggressive than these native fish.
As the round goby takes over the niche of the mottled sculpin, it is also taking on its predators. The fisheries of the Great Lakes are mainly composed of piscivore species, or fish eating fish. Thus the goby as a potential food source has direct implications on these fisheries. Round goby predation has been recorded for rock bass, smallmouth bass, stonecat, tubenose goby, brown trout, walleye, yellow perch, mottled sculpin, lake sturgeon and lake trout. Of most importance in this list is the endangered lake trout due to the unknown effects the goby will have on the maintenance or decline of this population (Jude, 1997).
The effects an invasive species has upon other organisms in an ecosystem are often hard to predict, and many times are realized after we begin to see overarching trends. Recruitment losses due to goby presence have been noted for lake trout (Salvelinus namaycush), lake sturgeon (Acipenser fulvescens), and smallmouth bass (Micropterus dolomieu) due to predation upon eggs and larvae (Corkum, 2004). Many studies have documented the aggressive foraging of round gobies specifically on smallmouth bass eggs. Gobies have the ability to consume, on average, an entire unguarded nest of smallmouth bass eggs in about 15 minutes (Jude, 1997). Only the future will tell if this new interaction will have devastating consequences for smallmouth bass populations.
Gobies feeding preferences include benthic organisms that have been exposed to contaminated sediments in waterways, resulting in bioaccumulation of toxins in the food web. For instance, the zebra mussel’s filter-feeding biomagnifies contaminants in the water column which are then passed to the predating goby. Since the goby has become a regular component of the diet in sport and commercial fishes, these toxins continue to accumulate and magnify in top predators. To assess the implications to human health, a study was done showing the concentrations of PCBs in aquatic biota before and after goby invasion, and results indicated an increase in PCB concentrations after invasion (Corkum, 2004). Gobies have also been identified as a potential cause of increased waterfowl death from botulism (Clostridium botulinum type E). Again, biomagnification of this disease from zebra mussels through gobies and into fish eating birds is the expected path of transmission. A higher concentration of round goby was found in the guts of infected migratory birds vs. uninfected birds for a variety of species: Common Loon (Gavia immer), Herring Gull (Larus argentatus), Ring-billed Gull (Larus delawarensis), Long-tailed Duck (Clangula hyemalis), and Red-breasted Merganser (Mergus serrator) (Corkum, 2004). Overall, alterations of the food web structure and coinciding shifts in predator diets has put the viability of these affected ecosystems, which are already plagued by a host of other invasive species and anthropogenic pressures, at further risk.
The round goby is a natural predator of the zebra mussel, the success of the zebra mussel’s invasion has facilitated the success of the round goby (Vanderplog et al. 2002). This facilitation occurred because not many native species used the zebra mussel as a food source because the mussel’s shell was much harder to break compared to the native clams’ shells. The round goby is able to ingest zebra mussels because they contain upper and lower molariform teeth (Figure 7) which all efficient molluscivores contain. Smaller gobies have a larger variety when it comes to their diet, whereas larger gobies almost purely rely on zebra mussels as their nutritional source (Djuricich and Janssen 2001). A round goby can eat about 36 gobies per day (Ghedotti et al. 1995) because of this figure the thought of biomanagment of the zebra mussel by the round goby was hypothesized. Unfortunately, the round goby would not act as an effective management technique for two reasons. First of all, round gobies are non-selective when it comes to food and therefore will eat “whatever is closer” (Ghedotti et al. 1995). Secondly, round gobies lack a swim bladder so they are not effect predators vertically in the water column (Ghedotti et al. 1995) gobies are only effective predators along the bottoms of water columns. Lastly, now that the zebra mussel has been included into the food web via the round goby all of the toxins now have another vector to enter the food chain. Round gobies have made the biomass of the zebra mussels indirectly available to piscivores and waterfowl.
Figure 7. This shows the upper and lower pharyngeal teeth of a round goby (Ghedotti et al., 1995).
Biomagnification is the accumulation of substances in a living organism with the food intake. Simple organisms such as algae can absorb minute quantities of a substance which are transferred through the food chain to higher living species such as fish and birds. Biomagnification along a food chain will result in the highest concentrations of a substance being found at the top of the food chain (“Glossary”). Since 1999 over 50,000 loons and other birds have died of botulinus poisoning in Lake Erie (“Exotic Species Invasion” 14 June 2004). Botulinus refers to the aquatic bacteria, Type E Botulism. This toxin occurs in lake bottoms that are rich in vegetative decomposition (Domske 2004). Type E botulism enters the food web via filter feeds, such as zebra mussels. The zebra mussels are filter feeders and therefore they receive their nutrients from the sediments in the water column. The zebra mussels are then ingested by round gobies, which are in turn eaten by piscivorous fish or waterfowl. The piscivorous fish could then be eaten by waterfowl and humans (Figure 8).
Figure 8. Displays the seven tiers of biomagnification with respect to Type E botulism (Adapted from: Domske 2004).
The botulinum toxin binds to nerve receptors which lead to descending paralysis (Domske 2004). Therefore infected individuals move slower become an easier target for predators. A study was done from May 2002 to May 2003 to determine the toxicity of gobies compared to other fish. About a hundred individual fish were collected (round gobies, smallmouth bass, largemouth bass (Micropterus salmoides), northern pike (Esox lucius), crappie (Pomoxis annularis), bluegill (Lepomis Macrochirus) and yellow perch (Perca flavescens)) from the Pennsylvania shores of Lake Erie and tested for botulinum and various metals (Domske 2004). All of the samples came back negative for botulism, but there was arsenic and mercury present. Therefore the scientists concluded by saying that multiple stressors need to be examined in order to better understand this problem of Type E botulism biomagnification. Arsenic and mercury do lower the immune systems of individuals containing certain concentrations (Domske 2004). This study did not coincide with the number of fish kills for those two years. At the end of 2002, 17301 avian birds had died of botulism and in 2003, 3008 avian birds died on Lake Erie due to botulism (Domske 2004). This shows that Type E botulism is not a problem throughout Lake Erie, but rather in certain locations. Type E botulism is harmful to humans and cannot be “cooked out” therefore the round goby has now acquired the potential ability to negatively affect human health as well (Domske 2004).
The round goby is obviously changing the North American ecosystems that it has invaded. The goby is out competing smaller fish that occupy the same niche or require similar resources. They are preying upon piscovorous fish eggs which are declining the number of young of the year for these native fish. By pushing out smaller native fish the larger piscovorous fish are being forced to change the composition of their diet. Also, they have increased the effect that botulism is having on the avian bird population in Lake Erie along with potentially threatening human health.
Humans have had a crucial role in the introduction and success of the round goby introduction. Most importantly, people are the ones who introduced the round goby into North America. As mentioned before, it is very probable that the round goby was brought to the Great Lakes through the discharging of ballast water (Camp et al. 1999).
Secondly, anglers have a large impact on the dispersal of the round goby. The lack of knowledge, type of bait used, and fishing during native species spawning seasons all affect the success rates of the round goby. The sculpin and round goby look very similar and are often times mistaken for the same fish. Many times anglers are “catch and release fishermen” and when a goby is caught it may be thrown back in the water not realizing it is an exotic species. Anglers also have the right to collect their own live bait or purchase it. Although, the use of gobies is illegal (New York State Department of Conservation) the option and availability of this fish still exists. Fishermen need to be aware of what type of live bait they are using and must properly dispose of any unused bait. Ignorant anglers may facilitate the spread of round gobies in an acute manner. By dumping unused bait into the water or using the round goby as bait creates another opportunity for the round gobies invasive success.
As mentioned in the round gobies life-cycle, this invasive species predates on native fish eggs, especially the smallmouth bass. Anglers promote this destructive act when fishing during native spawning seasons or purposefully pulling male bass off of their nests. According to the NYS DEC the season of large/smallmouth bass is the, 3rd Saturday in June through November 30th. These dates have been established in order to prevent anglers from fishing these species during their spawning times. However, fish do not spawn according to the human calendar but rather by climatic conditions such as temperature. Therefore, if we experience a longer winter and the waters of New York do not warm up to suitable spawning temperatures the bass will wait until suitable conditions. Therefore, the fishing regulations in some years may not accomplish their original goal. This promotes the success of the round goby because if a bass is pulled from its nest the goby has free access to the bass’ eggs. On average a male bass is kept off its nest for only three minutes, however, gobies eat twenty eggs per minute (Zappia 22 June 2003). Therefore, anglers are giving gobies a free meal along with decreasing the amount of native yearlings that hatch in a season.
There are currently different education attempts in the Great Lakes region on the Canadian and American sides. The Ontario Federation of Anglers and Hunters is trying to spread awareness and monitor the spread and impact of the round goby (Ontario Federation of Anglers and Hunters). The organization Sea Grant has been trying to spread awareness and monitor the goby also (“Sea Grant”). Resources such as fact sheets and watch cards have been created (Appendix I) and distributed. There have been countless publications concerning the round goby however; it seems we have yet to determine how to control this invasive species. Currently in northern New York State there is very little being done concerning the goby. Region 6 of the NYS DEC exclaimed that the North Country is not doing anything to control or eliminate the round goby. They do not have the resources at this point, and the resources would not become available until the round goby became a problem in watersheds of northern New York. Fortunately, a student at St. Lawrence University, Erin Woodward, and Dr. Brad Baldwin has been conducting research on the tolerance levels of the round goby in different salinities. Erin and Brad worked with Rivers Docs during the summer of 2004 to spread awareness of the round goby to citizens of Northern New York (pers. comm. Erin Woodward).
Our lack of knowledge of the effects of management techniques promotes the success of the round goby. There are many ideas and methods for controlling the round goby however, these methods have not been researched or tested to know the exact consequences of the technique. For example, electric grids and rotenone are two examples of suggested control techniques (Charlebois et al. 1997). An electrical barrier was constructed on the Des Plaines River, Illinois, to decrease the number of non-indigenous fish moving from the Great Lakes to the Mississippi River (Corkum 2004). Unfortunately, the barrier is not preventing the spread of the round goby because the goby moved downstream before the barrier was energized (Corkum 2004). Hopefully, the barrier will help reduce the spread of other exotic species such as the big head and silver carp (Hypophthalmichthys sp.).
The manipulation and redesign of waterways also has a major impact on the round goby expansion and other invasive species. For example, Niagara Falls is a natural barrier that prevents the safe passage of ships and fish in-between Lake Ontario and Lake Erie. However, that all changed in 1829 when the Welland Canal was established and enabled cargo ships, boats and even freshwater fish to move with ease throughout the Great Lakes (“Welland Canal”). This canal made it possible for exotic species to move throughout all the Great Lakes and attempt to invade the different rivers and tributaries that are connected.
Dams are anthropogenic disturbances that fragment waterways. Usually, resulting in negative connotations about their influence on the ecosystem, however, in some cases, such as the round goby, the fragmented waterways have helped prevent the spread of this exotic species into tributaries of the Great Lakes and more specifically the St. Lawrence River. In Northern New York there are eight watersheds that contain rivers, streams, lakes and ponds that are connected to the St. Lawrence River (Appendix II) Only one of these eight watersheds does not contain at least one dam on its system of waterways. The upper St. Lawrence watershed which borders the majority of the St. Lawrence River contains five dams where the seaway connects with its tributaries. There are over thirty dams within the Northern New York watersheds. These anthropogenic disturbances may have negatively altered the natural ecosystem, but it has created a barrier to prevent the exotic round goby from expanding its territory by swimming up the tributaries themselves. This shows that the fragmentation of habitat is not completely detrimental.
Anthropogenic activities have introduced and aided in the success of the invasion of the round goby. Our lack of knowledge led to the introduction and dispersal of the round goby. Our manipulations of waterways have had both a positive and negative impacts on the dispersal of the round goby. Attempts at education have not reached all people who have the ability to help prevent or decline the population of the round goby. Finally, we need to determine an efficient method for management.
The government issues surrounding the round goby situation revolve almost entirely around the regulation of BWE in one way or another. Our aim is to point out the general history of the issues as they relate to what is happening today at the international, national, and regional levels. In the interest of concision, and with regard to the fact that a review of the literature relating to ballast water management could span volumes, we will only review the main relevant issues and recent events.