Formerly known as Bythotrephes cederstroemii (Berg and Garton, 1994; Yan and Pawson, 1998; Berg et al., 2002; Therriault et al., 2002).  spiny water-flea

Bythotrephes longimanus is a visual predator, using its large compound eye to detect zooplankton (Azan et al., 2015). They consume 75% of their body weight each day in prey items (Lehman et al., 1997).

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

Environmental	Socioeconomic	Beneficial

Bythotrephes reproduce rapidly and consume small zooplankton such as small cladocerans, copepods, and rotifers, potentially competing directly with planktivorous larval fish for food (Berg and Garton, 1988; Evans, 1988; USEPA, 2008; Vanderploeg et al., 1993). At times, its consumption may even exceed that of zooplankton production (Bunnell et al., 2011).

A decline in native cladocerans following the introduction of Bythotrephes has been observed in Lake Huron and Lake Michigan (Barbiero and Tuchman, 2004). In Lake Erie, the detection of Bythotrephes in 1985 was also accompanied by a decline in multiple species of cladocerans (e.g., Eubosmina coregoni, Daphnia mendotae, D. retrocurva), including an almost complete absence of Diaphanosoma spp. wherever Bythotrephes was present in 1986 (Barbiero and Rockwell, 2008). This study further documented a lack of spatial overlap between Bythotrephes and Leptodora (a native water flea). This is in concordance with many other studies which have documented a negative correlation between abundance of the two species, implying that competition and/or predation from Bythotrephes has played a significant role in declines of Leptodora (e.g., Branstrator, 1995; Fernandez et al., 2009; Foster and Sprules, 2009; Garton et al., 1990; Lehman and Cáceres, 1993; Yan and Pawson, 1997). Interestingly, Leptodora coexists with and often outnumbers Bythotrephes in European lakes, which could be due to higher abundance of available zooplankton prey or lower levels of planktivory in combination with the greater conspicuousness of Bythotrephes (Foster and Sprules, 2009). In Lake Michigan, the decline of D. retrocurva and D. pulicaria populations in contrast to relatively stable populations of D. mendotae has been attributed to the latter’s markedly faster escape responses (Pichlová-Ptácníková and Vanderploeg, 2011).

Some studies have documented an increase in chlorophyll a abundance with the invasion of Bythotrephes, potentially due to a release from grazing following increased predation pressure on zooplankton species (Barbiero and Rockwell, 2009; Hovius et al., 2007). This would imply that Bythotrephes is capable of affecting multiple trophic levels of the freshwater community. However, an increase in Bythotrephes abundance is not always correlated with an increase in chlorophyll a (Foster and Sprules, 2009; Strecker and Arnott, 2008). Notably, Strecker and Arnott (2008) demonstrated that invaded lakes experienced a significant reduction in secondary production, and hence a reduction in resources available in the epilimnion.

In some cases, Bythotrephes has been associated with a shift in cladoceran communities towards larger taxa over small possibly due to Bythotrephes predation of smaller species (Barbiero and Rockwell, 2008; Hovius et al., 2007; Yan and Pawson, 1997). Yet not all of Bythotrephes’ effects can be attributed to direct consumption. Vertical migration has also been observed in Daphnia spp. and copepod (e.g., Diacyclops thomasi, Leptomdiaptomus ashlandi, L. minutus) populations following Bythotrephes invasion, indicating that some species may migrate to deeper waters during the day to avoid Bythotrephes predation or competition (Bourdeau et al., 2011; Jokela et al., 2011; Lehman and Cáceres, 1993). Diel vertical migration may lead to an indirect negative effect on these native prey species, including reduced individual and population growth rates at lower temperatures (Pangle and Peacor, 2006; Pangle et al., 2007).

Meanwhile, the invasion of Bythotrephes has evidently had little or no negative effects on mysids (Foster and Sprules, 2009; Nordin et al., 2008) and rotifers (Barbiero and Warren, 2011; Hovius et al., 2007), and has sometimes been associated with increases in these populations. Bythotrephes has been implicated as a factor in the decline of alewife (Alosa pseudoharengus) in Lakes Ontario, Erie, Huron, and Michigan (Evans, 1988). However, recent studies suggest that Bythotrephes is a significant and even preferred prey item of alewife (Pothoven et al., 2007; Stewart et al., 2009).

Potential:
Significant increases in the trophic position of zooplankton (reduced herbivorous cladoceran biomass and increased omnivorous/predatory copepod biomass) and planktivorous fish such as the lake herring (Coregonus artedi) with the introduction of Bythotrephes has the potential to lead to substantial contaminant biomagnification in consumers (Rennie et al., 2011). However, increased mercury concentrations in consumers has not been observed following invasion; this may be attributed to increased increased foraging and growth efficiencies of consumers or to changes in the feeding habits of omnivorous prey (Rennie et al., 2011).
 

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

Realized:
The first noticeable impact of Bythotrephes was on fishermen. The tail spines of Bythotrephes hook on fishing lines, fouling fishing gear. This problem has largely been eliminated with a switch to line/gear types less susceptible to Bythotrephes fouling.

There is little or no evidence to support that Bythotrephes longimanus has significant beneficial effects in the Great Lakes.

Realized:
Bythotrephes is a food source for fish including yellow perch, white perch, walleye, white bass, alewife, bloater chub, Chinook salmon, emerald shiner, spottail shiner, rainbow smelt, lake herring, lake whitefish, and deepwater sculpin (Branstrator and Lehman, 1996; Bur et al., 1986; Makarewicz and Jones, 1990). However due to its long tail spine, predation of Bythotrephes is mainly restricted to larger fish and non-gape limited species (Pothoven et al., 2007).
 

Potential:
There is speculation that Bythotrephes may control the abundance of Cercopagis pengoi through competition and predation (Vanderploeg et al., 2002).

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

Control
Like the confamilial fishhook waterflea (Cercopagis pengoi), the spiny waterflea is most likely to be spread on aquatic equipment, especially fishing lines. Consequently, public education is a significant method of control which can greatly reduce incidences of species transfer by unaware or incautious anglers (Jacobs and MacIsaac, 2007; Lui et al., 2010).
 

Biological
Bythotrephes longimanus is consumed by rainbow smelt, lake herring, lake whitefish, yellow perch, white perch, white bass, walleye, alewife, bloater chub, emerald shiner, spottail shiner, deepwater sculpin, and chinook salmon in the Great Lakes (Bur et al., 1986; Makarewicz and Jones, 1990; Branstrator and Lehman, 1996). Bythotrephes longimanus’ defensive tailspine has been observed increasing in size throughout the summer in response to predation pressure (Straile and Halbich, 2000). Consequently, larger fish are more likely to be successful predators (Branstrator and Lehman, 1996).  The opossum shrimp (Mysis relicta) has been observed eating B. longimanus in Ontario lakes, but the frequency of consumption appeared related to abundance of the invader and alternate prey (Nordin, 2008).

Physical
Bythotrephes longimanus collects in gelatinous clumps on fishing lines, downrigger cables, and other aquatic equipment (Lui et al., 2010). Responsible maintenance and cleaning methods are recommended to prevent spread between water bodies, including cleaning all aquatic equipment with high pressure (>250 psi) or hot (>50°C) water after each use (Ontario’s Invading Species Awareness Program). The acute upper lethal temperature level for B. longimanus, at which death occurs rapidly, is 40°C (GLMRIS, 2012), and a study found that B. longimanus specifically requires 10 minutes treatment with 43°C water to ensure 100% mortality (Beyer et al., 2011). Fishing lines designed specifically to prevent the spread of waterfleas, such as the Flea Flicker brand, have been proven effective in significantly reducing fouling on lines, indicating their importance as a management tool (Jacobs and MacIsaac, 2007).

Electron beam irradiation has been used to control microorganisms in aquatic pathways, including Bythotrephes longimanus (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 B. longimanus 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
There are no known 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.