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

Socioeconomic	Beneficial

H. anomala has a broader, more flexible diet than other zooplankton native to the Great Lakes (Evans et al., 2018; Marty et al., 2012). Additionally, this species has higher attack rates and lower prey handling times when compared to native species of Mysis (Dick et al., 2012). These characteristics give them a competitive advantage compared to native zooplankton species, and may affect the characteristics of plankton assemblages in the Great Lakes. In a mesocosm experiment, H. anomala predation selected for larger daphnia (Sinclair et al., 2016).

Potential:
Ponto-Caspian mysids differ from the North American mysid, Mysis relicta, in their adaptation to warmer temperatures (Bondarenko and Yablonskaya 1979). Therefore, H. anomala could become abundant in many areas of the Great Lakes, including littoral zones that are currently devoid of mysids. However, increased water clarity in shallow waters may instead inhibit such migration (Ricciardi et al. in press).

Based on its impacts in some European reservoirs (Ketelaars et al. 1999), H. anomala may reduce zooplankton biomass and diversity in invaded areas, with cladocerans, rotifers, and ostracods being most affected. Hemimysis anomala may compete with, or prey upon, other invertebrate predators, such as Bythotrephes longimanus and Leptodora kindti. Its omnivory may also reduce local phytoplankton if small-sized juvenile mysids are abundant (Ketelaars et al. 1999); however, phytoplankton biomass typically increases (sometimes doubling) in lakes following mysid invasions (Borcherding et al. 2006). It is not known whether plankton consumption by H. anomala affects other planktivorous organisms. Dumont and Muller (2010) remarked that there was no decrease in zooplanktonic hydra (Pelmatohydra oligactis) or juvenile roach (Rutilus rutilus) in areas with large H. anomala densities, although this evidence was largely anecdotal. In general, lake productivity seems to influence the degree of mysid impact, with less productive, nutrient-poor lakes being more affected by the competition and predation following mysid invasions (Ricciardi et al. in press).

Hemimysis anomala feeds rapidly, even at low prey densities, and its fecal pellets may alter the local physico-chemical environment (Ketelaars et al. 1999, Olenin and Leppäkoski 1999, Pienimäki and Leppäkoski 2004). A mysid introduction can also increase the biomagnification of contaminants in piscivores through a lengthening of the food chain; for example, concentrations of polychlorinated biphenyls and mercury in fishes have been shown to be higher in lakes containing mysids than in mysid-free lakes (Cabana et al. 1994, cf. Rasmussen et al. 1990). Furthermore, through direct transmission and indirect effects on the food web, introduced mysids may cause increased parasitism by nematodes, cestodes, and acanthocephalans in fishes (Lasenby et al. 1986, Northcote 1991).

There is little or no evidence to support that Hemimysis anomala has significant socio-economic impacts in the Great Lakes.

There is little evidence to support that Hemimysis anomala has significant beneficial effects in the Great Lakes.

Hemimysis anomala is considered a high-energy food source due to its lipid content, which can increase growth rates for planktivores (Borcherding et al. 2006). However, the nutritional value of H. anomala can vary depending on the food source and trophic position of the individual (Marty et al. 2010). A recent caloric density analysis in Lake Ontario indicates that H. anomala appears to be a lower quality food source than native mysid M. diluviana but higher than most zooplankton (Walsh et al. 2010).

In many regions, including the Great Lakes basin, perch (Perca spp. and Morone americana) is known to feed on H. anomala, as is rock bass (Ambloplites rupestris) (Brooking et al. 2010, Lantry et al. 2010). In Lake Ontario, recent surveys indicated that H. anomala was a predominant food item of alewife (Alosa pseudoharengus), an important forage fish, in the sampled area (Lantry et al. 2010). Moreover, stable isotope analysis suggests that H. anomala may be replacing zooplankton in the diet of young yellow perch (Yuille et al. in press). It appears that as H. anomala density increases, this species plays a more substantial role in supporting higher trophic levels (Yuille et al. in press).

However, the net effect of this new prey item on its predators’ populations in the Great Lakes is currently unknown. In some lakes, mysid (Mysis spp.) introductions have preceded the increased growth of salmonids; in contrast, in other lakes they are associated with rapid declines in abundance and productivity of pelagic fishes (Lasenby et al. 1986, Langeland et al. 1991, Spencer et al. 1991). Through its predation on benthic invertebrates and detritus, H. anomala could become a significant part of the local benthic food web in areas containing appropriate habitat and shelter for H. anomala (Kestrup and Ricciardi 2008). Furthermore, analysis of carbon and nitrogen stable isotopes indicate that H. anomala may obtain carbon from both littoral and pelagic sources, potentially linking these two zones in the food web (Marty et al. 2010).

Regulations
 

Hemimysis anomala is listed in New York as a prohibited invasive species (6 NYCRR Part 575). In Wisconsin, Hemimysis anomala is a prohibited invasive species (Wis. Admin. Code § NR 40.04), meaning that it is unlawful to transport, possess, transfer, or introduce the species within or into the state without a permit as defined under Wis. Admin. Code § NR 40.06.

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

Control
Biological
In Lake Ontario, H. anomala has been documented in the stomachs of alewife (Alosa pseudoharengus), rock bass (Ambloplites rupestris), yellow perch (Perca flavescens), and white perch (Morone americana) (Lantry et al. 2010, Brooking et al. 2010). Alewives were the only predators exhibiting significant consumption of H. anomala, likely due to their nocturnal feeding habits (H. anomala exhibits diel vertical migration, remaining near the lakebed during the day and emerging at night), and their prior experience consuming the Great Lakes native mysid Mysis relicta (now referred to as M. diluvania), which exhibits similar swimming behavior to H. anomala (Lantry et al. 2010). Lantry et al. (2010) suggest that as the density and spatial distribution of H. anomala expands, more Great Lakes fish will become successful predators. Round goby (Apollonia melanostoma) are accomplished molluscivores, but have also demonstrated specific predatory behavior enabling them to consume M. relicta, and may become significant predators of H. anomala in the absence of dreissenids (Lantry et al. 2010). H. anomala has also been documented in yellow perch and white perch diets in Lake Oneida, New York (Brooking et al. 2010).  The significance of fish predation on control of H. anomala is currently unknown, but there is potential for adaptation towards consumption among Great Lakes zooplanktivores, especially because it is considered a high-energy food source (Borcherding et al. 2006).

Physical
H. anomala exhibits mortality at temperatures below 0° C (Borcherding et al. 2006). Because H. anomala is a new, quickly spreading invasive species, preventative measures are encouraged for boaters traveling between water bodies, including visually inspecting boats, trailers, and equipment for plants, animals, and mud after each use, draining water from the motor, live well, bilge, and transom wells while on land, and rinsing all equipment with high pressure (>250 psi) or hot (>50°) water (Ontario’s Invading Species Awareness Program).

Electron beam irradiation can be used to control microorganisms in aquatic pathways, including Hemimysis anomala (GLMRIS 2012). Electron beam irradiation is a non-selective control method which exposes water to low doses of radiation using gamma-sterilizers or electron accelerators, breaking down DNA in living organisms while leaving behind no by-products (GLMRIS 2012). Ultraviolet (UV) light can also effectively control microorganisms including H. anomala in water treatment facilities and narrow channels, where UV filters can be used to emit UV light into passing water, penetrating cell walls and rearranging DNA of microorganisms (GLMRIS 2012).

Chemical
H. anomala tolerates salinity of 0-19 ppt (parts per thousand) (Bij de Vaate et al. 2002). Ellis and MacIsaac (2008) tested the salinity tolerance of Great Lakes Invaders in ballast water exchange (BWE) simulations. They documented 100% mortality for H. anomala after 5 hours in a simultaneous BWE treatment, in which salinity was gradually increased from 4-30 ppt, and 100% mortality after 3 hours in a sequential BWE treatment, in which species are immediately exposed to 30 ppt salinity.

The Great Lakes and Mississippi River Interbasin Study (GLMRIS 2012) suggests that alteration of water quality using carbon dioxide, ozone, nitrogen, and/or sodium thiosulfate could be effective in preventing upstream and downstream movement of crustaceans.

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