Echinogammarus ischnus

Invasion History

First Non-native North American Tidal Record: 1999
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 1999

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General Invasion History:

Echinogammarus ischnus is native to the Black and Caspian Sea basins and the surrounding inflowing rivers (Dediu 1980; Cristescu et al. 2004). It is known to survive and reproduce in salinities of 0 to18 PSU (Mordukhai-Boltovskoi 1964; Dediu 1980). Black Sea and Caspian populations show considerable genetic divergence (Cristescu et al. 2004). The development of canal systems permitted its spread into river systems of the Baltic and North Sea drainages (Jazdsewski 1980; Bij de Vaate et al. 2002; Konapacka 2002). By the 1990s, it reached the Elbe, Weser, and Ems rivers and the Rhine Delta (Bij de Vaate et al. 2002). In 1994 and 1995, E. ischnus was collected in North America in the Lake Erie and the Detroit River (Witt et al. 1995; Dermott et al. 1998). By 2009, its range extended from Duluth Harbor on Lake Superior (Trebitz et al. 2012) to Berthier-sur-Mer, about 40 km downstream of Quebec City, in the St. Lawrence River estuary (Radulovici et al. 2009). It has also colonized the upper Mississippi and lower Ohio rivers (Grigorovich et al. 2008), the Finger Lakes and Oneida Lake, in the interior of New York State (Cooper et al. 2012; USGS Nonindigenous Aquatic Species Program 2016), probably by canals, or possibly, trailered boats. Echinogammarus ischnus is a possible future invader in the Hudson River estuary, through the New York State Barge Canal, and could be transported by ballast water to other East Coast estuaries. Transport from the Great Lakes and upper Mississippi basin on trailered boats or fishing gear is also possible.

North American Invasion History:

Invasion History on the East Coast:

In 1994 and 1995, E. ischnus was collected in North America in the Lake Erie and the Detroit River (Witt et al. 1995; Dermott et al. 1998; USGS Nonindigenous Aquatic Species Program 2016). By 1998, it was found in Lake Huron, Lake Michigan, Lake Ontario and the upper St. Lawrence River (Dermott 1998; Nalepa 2001; USGS Nonindigenous Aquatic Species Program 2016). It was collected in Thunder Bay, Lake Superior in 2003 (Grigorevich 2005), and by 2005, it was found in Duluth-Superior Harbor (Trebitz et al. 2010). By 1999, it was collected in the St. Lawrence River estuary at Quebec City (Vanderploeg et al. 2002). In samples collected between 2000 and 2008, at Berthier-sur-Mer, about 40 km downstream of Quebec City, E. ischnus was identified by DNA barcoding (Radulovici et al. 2009).

Echinogammarus ischnus has colonized waterbodies adjacent to the Great Lakes, including the upper Mississippi-Ohio basin, and the Finger Lakes and Oneida Lakes in New York (NY). In 2004, E. ischnus was found at five locations on the upper Mississippi between River Miles 477 and 835, and at two sites on the Ohio River, at miles 471 and 584. By 2006, its distribution on the middle reaches of the two rivers was continuous. It has been recorded from sites in Iowa, Illinois, Kentucky, and Ohio. By 2012, it was extensively distributed in the Finger Lakes system in NY (USGS Nonindigenous Aquatic Species Program 2016). It was collected in Oneida Lake, NY in 2001 and is abundant there. The Finger and Oneida Lakes are connected to the Great Lakes by the New York State Barge (Erie) Canal (Cooper et al. 2012). Transport from the Great Lakes on barge fouling or on trailered boats is possible (Grigorovich et al. 2008; Cooper et al. 2012). Echinogammarus ischnus is expected to reach the Hudson River though the canal, but has not been reported yet.

Invasion History Elsewhere in the World:

Echinogammarus ischnus was first found outside the Ponto-Caspian basin in the Vistula River, Poland, in 1928, which it reached from the Dnieper River, a Black Sea tributary, via the Pripet-Bug canal (Jazdsewski 1980; Bij de Vaate et al. 2002; Konapacka 2002). In 1967-1971, it was dominant in the Vistula Lagoon, but it was absent in surveys in 1998-2000 and 2007, having been replaced by Dikerogammarus haemobaphes and Pontogammarus robustoides (Surowiec and Dobrzycka-Krahel 2008). It reached the Neman River, Lithuania by 1960 and by 1964, colonized the Curonian Lagoon (Latvia-Lithuania) (Olenin and Leppakoski 2008), probably also by canals linked to the Pripyat-Bug Canal (Bij de Vaate et al. 2002). Echinogammarus ischnus spread west, reaching Germany through canals joining the Elbe, Weser, and Ems rivers in the 1970s, the Rhine River by 1989, and the Rhine estuary by 1991 (Bij de Vaate et al. 2002). In 2008-2009, it was found in the Rhine, Meuse, and Seine River basins in France (Labat et al. 2011).

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Description

The body of Echinogammarus ischnus is laterally compressed, and lacks dorsal teeth. This species has strong sexual dimorphism, with the male longer than the female, and the male having a densely setose Antenna 2. It has a short, triangular rostrum. The eyes are kidney-shaped and twice as long as wide. Antennae 1 and 2 are roughly equal in length. Antenna 1 has a prominent accessory flagellum, with 17-22 segments. Antenna 2 has dense, long, curly setae in males, and moderate, shorter setae in females. Gnathopod 2 is larger than Gnathopod 1. The palms of the gnathopods are oblique and the dactyls are slender. The basipodite of pereiopod V is distally narrowed, without a postero-dorsal projection. Uropod 3 has a small scale-like inner ramus, less than half the length of the outer ramus. The exopod is relatively long, encircled by up to five rows of setae and tipped with a short spine. The telson is cleft to the base with two dorsal and three apical spines on each lobe. Males are 6-15 mm and females are 5-13 mm in size. This description is based on Köhn and Waterstraat 1990; Witt et al. 1997; and Crosier and Molloy 2003.

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Taxonomy

Ecology

General:

Echinogammarus ischnus has separate sexes, the young are brooded, and development is direct (Bousfield 1973). The animals mature at ~4.8 mm (Crosier and Molloy 2003). This amphipod bears up to 20 eggs, depending on body size (Kohn and Waterstraat 1990). They mature in 44-65 days over the temperature range of 20-24°C, and have 2-3 generations per year (Kohn and Waterstraat 1990; Crosier and Molloy 2003).

Echinogammarus ischnus tolerates a wide temperature range, from near-freezing to above 30°C (Dediu 1980). In its native range, it occurs in the Caspian Sea and Black Sea estuaries (Mordukhai-Boltovskoi 1964; Dediu 1980). It ranges widely into freshwater, but is sensitive to water of low ionic content (conductivity). Growth and survival was reduced at low conductivities (108 µS/cm), after heavy river flow, and better at higher conductivity (300 µS/cm), reflecting its evolution in saline waters (Kestup et al. 2010). In tests of simulated ballast water exchange, a small proportion (~1-5%) of E. ischnus survive after exposure for 48 hours to a salinity of 30 PSU. In its introduced range, E. ischnus is abundant on rocky and cobble shores, but especially favors clumps of Zebra and Quagga Mussel (Dreissena) shells. It is not strongly associated with vegetation (Dermott et al. 1998; Nalepa 2001) and may be more vulnerable to fish predation in vegetation than the North American native Gammarus fasciatus (Gonalez and Burkett 2004). The Dreissena invasion in Europe and the Great Lakes-St. Lawrence River may have facilitated the spread of E. ischnus by providing shelter from predation (Kohn and Waterstraat 1990; Kang et al. 2007). In the St. Lawrence River, it was positively correlated with dreissenid mussels, coarse gravel sediment, and increasing current (Palmer and Ricciardi 2004).

Echinogammarus ischnus is an omnivore, feeding on algae, aquatic plants, and occasional invertebrates (Barnes 1983; Krisp and Maier 2005), including other amphipods, such as G. fasciatus (Kestrup and Ricciardi 2009). However, in a comparison of adults and juveniles of five introduced and one native gammarid amphipod in Poland, had a relatively low trophic level (Bacela-Spychalska et al. 2013). Aside from Gammarus fasciatus in North America, and several Ponto-Caspian amphipods in Europe, fishes are the major predators of E. ischnus (Palmer et al. 2005). In the St. Lawrence River, a fungus of the Saprolegniaceae infects E. ischnus, and causes greater mortality to it, than to G. fasciatus, facilitating the coexistence of the two species (Kestrup et al. 2011).

Food:

detritus, algae, invertebrates

Consumers:

Fishes

Trophic Status:

Omnivore

Omni

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Habitats

General Habitat	Nontidal Freshwater	None
General Habitat	Grass Bed	None
General Habitat	Coarse Woody Debris	None
General Habitat	Rocky	None
General Habitat	Marinas & Docks	None
Salinity Range	Limnetic	0-0.5 PSU
Salinity Range	Oligohaline	0.5-5 PSU
Salinity Range	Mesohaline	5-18 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None

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Tolerances and Life History Parameters

Minimum Temperature (ºC)	0	Dediu 1980
Maximum Temperature (ºC)	30	Dediu 1980
Minimum Salinity (‰)	0	None
Maximum Salinity (‰)	18	Mordukhai-Boltovskoi 1964; Dediu 1980)
Maximum Length (mm)	15	Males, Females 13 mm, Europe (Crosier and Malloy 2003); Lake Kummerow, Germany. Females reached 8 mm (Kohn et al. 1990; 9.1 mm adult male, 5.3 adult female (Witt et al.1997, Detroit River, Ontario)
Broad Temperature Range	None	Cold temperate-Warm temperate
Broad Salinity Range	None	Nontidal Limnetic-Mesohaline

General Impacts

Echinogammarus ischnus has replaced the native Gammarus fasciatus (Dermott et al. 1998) at many locations in the Great Lakes and St. Lawrence River through predation and competition, but this may also be due to selective predation by the Round Goby (Neogobius melanostomus) (Van Overdijk et al. 2003; Kestrup et al. 2011a). However, G. fasciatus persists in many locations, with competition mediated by environmental factors. Low conductivity, due to spring river flows, reduces the competitiveness of E. ischnus, as does a fungus, to which E. ischnus is more vulnerable (Kestrup and Ricciardi 2009; Kestrup et al. 2011b).

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Regional Impacts

GL-III	Lake Ontario		Ecological Impact	Competition
Echinogammarus ischnus has largely replaced the native Gammarus fasciatus (Dermott et al. 1998), in the upper St. Lawrence River, but this may be due to selective predation by the Round Goby [Neogobius melanostomus (Overdijk et al. 2003)], or due to abiotic factors such as calcium concentration and conductivity (Kestrup and Ricciardi 2009).
B-VII	None		Ecological Impact	Competition
In the Vistula Lagoon, E. ischnus was classified as having a moderate level of community impacts (Zaiko et al. 2011).
GL-III	Lake Ontario		Ecological Impact	Predation
In the upper St. Lawrence River, Echinogammarus ischnus and Gammarus fasciatus are mutual predators, with E. ischnus prevailing at higher conductivity, and declining due to predation duiring periods of lower conductivity and heavy spring riverflows (Kestrup and Ricciardi 2009).

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