Invasion of the Round Goby

Benthic predator threatens sport fishery but eats zebra mussels

Dec 20, 2019

First posted 20 Dec 2019; Modified 28 July 2021

Round Goby (Neogobius melanostomus) is a European fish that has invaded the Mohawk Watershed from waterway connections to the Great Lakes. They first invaded the Great Lakes by hitchhiking in ballast water from ships arriving from Europe. But now that they have spread across the Great Lakes, they are starting to move into tributaries. The Erie Canal allows passage across watershed boundaries, including the Hudson Watershed. At this point, the species has migrated from west to east down the Mohawk: in 2019 the Round Goby had only been documented in the Erie Canal in the westernmost part of the Watershed (* see note at end of the post: four fish were captured in the Hudson River in July 2021). Three important points fall from these observations: they are here, they eat eggs of other fish, and they also eat zebra mussels, an invader already here.

At this point in the invasion it is downhill to the Hudson, so there is a major concern that this species will spread quickly as it invades the first watershed outside the Great Lakes. This little fish may cause big trouble for the sport fishery in the Mohawk, which is primarily focused on Smallmouth bass and Walleye. My interest in this invasion was piqued earlier this year when Scott George and colleagues at the USGS presented their findings at the Mohawk Watershed Conference (George and others, 2019). After looking into the details of the invasion, I now have a better appreciation of the gravity of this situation.

The success of the Round Goby is based on several characteristics that make it a major problem: it tolerates a wide range of environmental conditions and it has a diverse diet. It apparently has aggressive behavior in feeding and spawning and as a result has become the dominant benthic fish in many areas of the Great Lakes. Its aggressive feeding, especially on eggs of local native fishes, is seen as a particular issue (Johansson and others, 2018).

The accidental introduction of the Round Goby from ballast water into Lake St Clair in 1990 was a big deal, as was the subsequent spread to all the Great Lakes in the following five years. Dumping freshwater ballast from outside the Great Lakes basin is now prohibited, but dumping ballast water within the basin has been blamed for the spread of the Round Goby across the Great Lakes. The spread out of the Great lakes and into the Mohawk and Hudson watershed is also a big deal because of the consequences for the ecosystem, explored below. Round Goby was first documented in the Mohawk Watershed in 2014.

From Europe to your doorstep in thirty years. The invasive Round Goby (Neogobius melanostomus) – one of the world’s top invasive fish in fresh water ecosystems. Photo by Peter van der Sluijs, reproduced here under Creative Commons license (background modified).

To address invasion, the USGS initiated a three-year study in 2016 on the occurrence of the Round Goby in the Mohawk Watershed. The study was lead by Barry Baldigo and Scott George of the US Geological Survey (USGS) and Christopher Rees and Meredith Bartronof the NE Fishery Center (US FWS). The primary goal of their study was to evaluate and establish the nature and extent of the Round Goby in the watershed. The objective was to use different methods to determine the occurrence of fish, including seining, trawling, electrofishing, and eDNA analysis.

The invasive highway

From the beginning, the very purpose of the Erie Canal was to connect waterways. Thus from opening day nearly 200 years ago it has allowed invasive fish species to migrate into the basin from both the east and the west. Recall that on the east end of the basin, the 90 ft Cohoes Falls was a natural barrier to most typical fish migration, but the Waterford Flight of locks allowed a new passage avenue. I recently wrote about River Herring, which use the locks to access the Mohawk. On the west end of the basin, the Erie Canal goes up and over the drainage divide and connects the watershed to the Great Lakes. In 2009 Norm McBride of the NYS DEC Fisheries division remarked on the effect that the Canal has on fish passage (see McBride 2009 below):

Completion of the Erie Canal in 1825 and the Erie Barge Canal in 1918 created a bypass around the Cohoes Falls that resulted in a direct waterway link between the Hudson River and Great Lakes. This bypass allowed fish to move east or west through the canal system to establish populations in other watersheds or within the Mohawk River. Fish moving west through the canal system include sea lamprey, alewife, and white perch. Fish moving eastward include smallmouth bass and gizzard shad. This movement through the canal system is still occurring. Freshwater drum, moving eastward, were first documented in 1990 at Lock 7 and are now present throughout the river.

The Round Goby is recognized as one of the top 100 invasive species globally (Johansson and others, 2018). So once the Round Goby was established in the Great Lakes, it seems like a matter of time before it found the western door to the Mohawk and Hudson watersheds.

Great Lakes invasion

The Round Goby came to the Great Lakes in ballast water from ships that transported them from the Ponto-Caspian region of Eastern Europe. Since establishment of a founding population in Lake St Clair in 1990, the Round Goby have been successful in spreading across all the Great Lakes in five years largely through ballast water transfer within the Great Lakes. Thus the rapid basin-wide establishment appears to be human-aided and less of a natural steppingstone migration, which would be much slower (Johansson et al., 2018).

Mattias Johansson and colleagues at the Great Lakes Institute for Environmental Research and the University of Windsor in Windsor, Ontario have been looking into the occurrence and dispersal of Round Goby in the Great Lakes, and a tool that they use is DNA from captured specimens.

The spread of these fish is partly natural (“steppingstone”), but in general is is thought that this process is relatively slow. These fish tend to have a high “site fidelity” measured in meters, but annual movements of kilometers have been documented. Commercial shipping and recreational boating are thought to facilitate movement across waterways, including rivers, streams, and canals. Round Gobies are no longer used as fish bait, but bait-bucket transfers have occurred and have the primary problem in several areas (Johansson and others, 2018).

DNA from Round Goby in the Great Lakes show that although fish may be largely related to the founding population in Lake St. Clair, they are relatively distinct in different geographic areas. The fish in eastern Lake Erie are thought to have been transferred there in dumping of freshwater ballast before entering the Welland Canal. The eastern Lake Erie fish are genetically distinct from western Lake Erie fish. Interestingly fish in eastern Lake Ontario are distinct from those in eastern Lake Erie, but more closely related to those in western Lake Erie and the Lake St. Clair founding population (Johansson et al., 2018). Thus it may be possible to use DNA to determine whether populations of fish in the Erie Canal from either Lake Erie or Lake Ontario - pathways are possible from both lakes.

eDNA

The work of Scott George and colleagues at the USGS and USNWS show that the Round Goby are here in the Mohawk Watershed. They have entered the watershed from the Great Lakes, but expansion eastward toward the Hudson has been slower then expected given capture rates and eDNA results. Capture of specimens by traditional means (seining trawling and trapping) have produced fish from Sylvan Beach (on Oneida) and in Rome. Thus the fish are clearly in the westernmost part of the watershed.

The early detection of invasive species in the aquatic environment has been revolutionized by eDNA (environmental DNA) testing. This technique allows the detection of cells from targeted species from a sample of water using quantitative polymerase chain reaction (qPCR). This technique has been used to show that the invasion of Asian Carp into the Great Lakes has begun (Jerde and others, 2011).

The results from eDNA testing for Round Goby in Mohawk River water is more ominous, and these analyses show the their presence in Rome and Marcy, just west of Utica. This is ominous because eDNA relies on the presences of cells from the fish in small water samples, so a hit (or repeated hits) means the fish are around and that it is unlikely that these are simply stray or lost individuals.

Invasion impacts

The fish have used Oneida Lake as a stepping stone to get to the Mohawk, so lessons learned there may be useful. Oneida Lake is part of the Erie Canal system on the Great Lakes side of the watershed divide; the canal continues east to Rome where it enters the Mohawk Watershed. Round Goby were first documented in nearby Onondaga Lake in 2011 and in western Oneida Lake in 2013; they had spread throughout the 80 sq mile Oneida Lake by 2014 (Rudstam and others, 2016). As noted above, the fish were first discovered in the upper reaches of the Mohawk, near Utica, in 2014. The recent (2021) capture of four fish in the Hudson River below the confluence with the Mohawk means that it appears to have taken eight years to transit the Mohawk.

Map showing Erie Canal and the Mohawk Watershed with reported arrival times of the Round Goby. Arrival in 2020 as far as Schenectady was reported on social media. Arrival in the Hudson River was reported and confirmed by the NYS DEC in July 2021 (see announcement here).

In a recent book entitled “Oneida Lake: Long-term dynamics of a managed ecosystem and its fishery,” Rudstam and colleagues consider the fate of the lake and the impact that the Round Goby may have on the sport fishery. They note that Round Goby feed on mussels, including the Zebra mussel that has fully invaded this and other waterways in this area.

Given the irreversible changes in the lake associated with dreissenid mussels [i.e. Quagga and Zebra], the effect of Round Goby is likely mainly positive as they represent a vector for moving energy bound in mussel biomass to the sportfish of interest to anglers. Potential negative effects include increased predation on fish eggs. However, there has been no negative effect of Round Goby on Smallmouth Bass populations in Lake Erie...

Scott George and colleagues (2016) wrote: “Round Goby populations have had profound impacts on fish assemblages in the Great Lakes drainage and other areas, although it is unlikely that they have substantially affected fish assemblages in the study area [Mohawk River] at this time.” But in 2019 George and colleagues warned:

This observed and anticipated expansion is concerning because Round Goby can outcompete native benthic fishes, consume the eggs of nest-building fishes such as Smallmouth Bass (Micropterus dolomieu), transfer contaminants to higher trophic levels (e.g., desirable gamefish), and carry the viral hemorrhagic septicemia (VHS) virus which has been linked to multiple fish kills in New York.

In 2019 I contacted Scott George at the USGS to get an update on the study. He wrote that the work is ongoing, and that in 2019 he and his team captured Round Goby as far east as the mouth of the Harbor Lock in Utica. The eDNA samples were positive 20-30 miles downstream from there, but there is a possibility of downstream transport, especially given the high flows on the Mohawk during sampling in 2019. Nonetheless, the recent data confirm the progressive march of these fish downriver toward the Hudson. At the time, he noted that the good news is that George wrote that the invasion is slower than expected. He noted:

A goby was captured in the canal in Utica in 2014 and the fact that we don't have any captures more than a mile or so downstream from that location by December 2019 is pretty remarkable. Goby have become more abundant in the Utica-Rome area during that period - but 5 years ago many of us expected goby would have already hit the Hudson by 2019.

Update 21 July 2021. The NYS DEC announced that four Round Gobies were captured in the Hudson River at two locations below the Troy Dam. A conclusion from this news is that this fish has apparently successfully used the Erie Canal to expand its range from the Great Lakes to the Mohawk River and now into the Hudson River. It seems likely that the fish now occur along the length of the entire main stem of the Mohawk River. The DEC reports that “...Marine Fisheries captured four round gobies at two locations in the Hudson River approximately 12 and 25 miles downstream of the Troy dam during routine fish sampling on July 13 and 14 marking the first documented occurrence of this invasive fish in the Hudson River.”

The announcement has worried John Waldman, Professor of Biology at Queens College, who has warned about the detrimental effect these fish may have on fishery in the lower Hudson, including Atlantic Sturgeon. In July 2021 he tweeted “…this little fish has the potential to become an ecological game changer and another example why prevention of invasives is the only good cure.”

This and other Notes from a Watershed are available at: https://mohawk.substack.com/

Notes from a Watershed - The Mohawk River

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