Gammarus obesus G.O. Sars, 1894, Pontogammarus obesus G.O. Sars, 1894, Niphargoides (Pontogammarus) obesus (Grimm.)

Nonindigenous Occurrences: Obesogammarus obesus occurs in Austria (NOBANIS 2014). It was recorded in the Pripyat River, Belarus in June 2008 (Semenchenko and Vezhnovetz 2008). In Germany, this species was first found in the Rhine River in 2004, and is reported to occur in the Danube River (Tittizer et al. 2000; Nehring 2006). Obesogammarus obesus has been collected in Szentendrei Duna, Dunaújváros, and Harta Rivers near Budapest, Hungary (Nesemann et al. 1995). It occurs in the Volga River, Russia as well as Ukraine (Bacela and Konopacka 2005; Berezina 2007). Reported in 2012 for the first time in the Amsterdam-Rhine canal near Nigtevecht, Netherlands and has since become established in the canal (Boonstra et al. 2016).

Potential pathway(s) of introduction: Transoceanic shipping (ballast water).

From its native range, Obesogammarus obesus was introduced to Germany through ballast water and sediment, and to Austria via floating structures, ballast water, and sediments (NOBANIS 2014). Cooling water systems of ships may also be a vector for the introduction of Obesogammarus obesus (Tittizer and Banning 2000). Currently, Obesogammarus obesus does not occur near waters connected to the Great Lakes basin. Obesogammarus obesus occurs within a major shipping route in Europe (Locke et al. 1993; Mills et al. 1993) and has established populations in the Amsterdam-Rhine canal in Amsterdam, a port city with direct trade to the Great Lakes. Ship assisted transport was the most likely vector of introduction into the Amsterdam-Rhine canal (Boonstra et al. 2016). Obesogammarus obesus is capable of surviving oceanic transport (Ricciardi and Rasmussen 1998). It does not produce resistant resting egg stages; ballast water exchange and flushing may limit egg transport and survival (Grigorovich et al. 2003).

Obesogammarus obesus has a high probability of establishment if introduced to the Great Lakes (Confidence level: High).

The native and introduced ranges of Obesogammarus obesus have similar climate and abiotic conditions to that of the Great Lakes (Reid and Orlova 2002; Grigorovich et al. 2003; U.S. EPA 2008). This species occurs in Belarus, which is located in similar latitudes as the Great Lakes basin (Semenchenko and Vezhnovetz 2008). This species can tolerate and adapt to a variety of environmental conditions and habitats (Pjatakova and Tarasov 1996; Bacela and Konopacka 2005). It is able to avoid unsuitable conditions and migrate to locate more suitable habitats (Berezina 2007). It can tolerate salinities from 0.1 – 20 ppt (Bij de Vaate et al. 2002; Berezina 2007). It is likely that Obesogammarus obesus can overwinter in the Great Lakes; it occurs in waters that have low temperatures and ice cover (Reid and Orlova 2002). Climate change may facilitate the establishment of this species in the Great Lakes basin; it occurs in areas that are warmer than the Great Lakes and is capable of surviving in higher salinities.

Obesogammarus obesus is a dietary generalist (Bij de Vaate et al. 2002; Elexová and Némethová 2003); it is likely that the Great Lakes contain an abundant food source for this species. This species is a significant portion of the diet of round gobies (Neogobius melanostomus), which are nonindigenous fish established in the Great Lakes basin; however, predation by these fish has not prevented the establishment of other amphipods to the Great Lakes such as Echinogammarus ischnus and Gammarus tigrinus, nor the establishment of Obesogammarus obesus where it has been introduced beyond its native range (Borza et al. 2009). Obesogammarus obesus can fit into narrow gaps in gravel and burrow in sediment to avoid predators, which is expected to account for its higher invasion potential relative to other Ponto-Capsian amphipods (Borza et al. 2018). The short generation time of Obesogammarus obesus may facilitate its establishment (Bij de Vaate et al. 2002). Dreissenid mussels, which are already established in the Great Lakes, may aid the establishment of Obesogammarus obesus; evidence suggests there is a positive relationship between the density of Obesogammarus obesus and the biomass of dreissenid mussels (Alexander Protasov pers comm). A closely related scud species, Echinogammarus ischnus, has a greater dominance over native Gammarus fasciatus in dreissenid beds (Dermott et al. 1998).

In the upper reaches of impoundments of the Danube River, Germany, Obesogammarus obesus attained densities up to 3,300 individuals/m2, which was associated with a displacement of several other amphipod species such as Dikerogammarus species. In other invaded portions of the Danube River, it occurred in densities as high as 10,668 ind/m2 (Borza et al. 2018). Obesogammarus obesus reaches high densities that are greater than or similar to the densities of the serious invaders or dominant species in the community (Žganec et al. 2009). This species is capable of migrating and dispersing with an average rate of 130 km/year (Leuven et al. 2009).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental

Obesogammarus obesus is an intermediate host of the tapeworm Amphilina foliacea (Dubinina 1974). Amphilina foliacea affects Acipenseridae species at 20–93% infection rates and reduces reproductive success (Bauer et al. 2002). Acipenseridae fish are infected by this tapeworm when it feeds on amphipods that carry it. Amphilina foliacea can potentially pose a hazard to lake sturgeon (Acipenser fulvescens), a near-threatened species of concern in the Great Lakes. Another host of Amphilina foliacea, Gammarus fasciatus currently occurs in the Great Lakes (Kipp 2014). Amphilina foliacea has not been reported in the Great Lakes but occurs in western North America (Choudhury and Dick 2001), so the threat of Amphilina foliacea due to the introduction of Obesogammarus obesus may be novel, but it is likely that its effects would be local.

There is evidence that it may outcompete other species; the high density of Obesogammarus obesus (3,300–10,668 individuals/m2) in the Danube River in Germany was associated with the displacement of several other amphipod species (Tittizer et al. 2000; Borza et al. 2018). By reaching high densities and preying on zoobenthos, Obesogammarus obesus has the potential to negatively impact zoobenthic populations (Elexová and Némethová 2003). As a prey of non-native round goby (Neogobius melanostomus), the presence of Obesogammarus obesus may result in an increase in population size of these invasive fish (Borza et al. 2009).

There is little or no evidence to support that Obesogammarus obesus has the potential for significant socio-economic impact if introduced to the Great Lakes.

It has not been reported that Obesogammarus obesus poses a threat to human health or water quality. There is no evidence that this species negatively impacts infrastructure, economic sectors, or the aesthetic appeal of the areas it inhabit. It has the potential to impact recreation by reducing the abundance of lake sturgeon; however, it is unknown if it has significant impacts.

There is little or no evidence to support that Obesogammarus obesus has the potential for significant beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Obesogammarus obesus can be used for the control of other organisms or improving water quality. There is no evidence to suggest that this species is commercially, recreationally, or medically valuable. It does not have significant positive ecological impacts.

*Ballast water regulations applicable to this species are currently in place to prevent the introduction of nonindigenous species to the Great Lakes via shipping. See Title 33: Code of Federal Regulations, Part 151, Subparts C and D (33 CFR 151 C) for the most recent federal ballast water regulations applying to the Great Lakes and Hudson River.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Biological
There are no known biological control methods for this species.

Physical
There are no known physical control methods for this species.

Chemical
There are no chemical control methods for this species.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.