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

Environmental	Socioeconomic

Current research on the environmental impact of Argulus japonicus in the Great Lakes is inadequate to support proper assessment.

Realized:
Argulus japonicus parasitizes the introduced channel catfish (Ictalurus punctatus) in Tichigan Lake, which adjoins the Fox River in Wisconsin as part of the Lake Michigan drainage system. However, it is most typically found on Carassius auratus and Cyprinus carpio in drainages in the United States (Amin 1981).

Potential:
Argulus japonicus can cause severe damage to the integument of its hosts, sometimes resulting in death. It can influence the appetite of a fish, subsequently affecting growth rates. It attaches to the skin, fins, or gills by way of suckers, and then feeds. It may also aid in the transmission of the spring viraemia of carp rhabdovirus (Rhabdovirus carpio), larval nematodes, and the fungal disease caused by Saprolegnia in some parts of the world (Avenant-Oldewage 2001, Gresty et al. 1993). Experiments indicate that it does not prefer its common host C. auratus over native North American species such as the fathead minnow (Pimephales promelas), nor is it more likely to detach from the latter as compared to the former (Lamarre and Cochran 1992).

Argulus japonicus is now widely distributed around the world and parasitizes many species of fish. In fact, it is probably capable of infecting almost all species of freshwater fish. It has been recorded on Labeo rohita, Catla catla, and Cirrhina mrigala in Pakistan; various cyprinids in Malaysia; tilapias, barbs, I. punctatus, Ctenopharyngodon idella, and other species in Puerto Rico and Cuba; and many species in South Africa, New Zealand, Britain, and other parts of Europe. It has the potential to cause increased stress in rainbow trout (Oncorhynchus mykiss), when it occurs in high densities. In South Africa it has been known to reach near epidemic levels in all fish species present in some water bodies, and has the potential to cause drastic effects in local fish populations (Avenant-Oldewage 2001, Bunkley-Williams and Williams 1994, Haond et al. 2003, Jafri and Ahmed 1991, Kruger et al. 1983, Pilgrim 1967, Rushton-Mellor 1992, Seng 1986).

Current research on the socio-economic impact of Argulus japonicus in the Great Lakes is inadequate to support proper assessment.

Potential:
Because it is capable of parasitizing many freshwater fish, it has the potential to affect populations of commercially or recreationally valuable species (e.g., catfish Ictalurus punctatus, tilapia Tilapia spp., or rainbow trout Oncorhynchus mykiss) (see above).

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

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

Control
Most control research conducted for Argulus spp. has been in the context of aquaculture and recreational fisheries pond management.

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

Physical
Gault et al. (2005) documented the effectiveness of “egg-laying boards” in control of the confamilial Argulus foliacus in a rainbow trout (Oncorhynchus mykiss) fishery. Lightweight, corrugated polypropylene boards were anchored and submerged within 6 mm of the water surface in a horizontal plane or floated vertically at varying depths to provide ideal egg-depositing surfaces for A. foliacus (Gault et al. 2005). Replacement of the boards at 2-week intervals and constant deployment throughout the A. foliacus breeding season significantly reduced the prevalence and intensity of parasite infection in trout, but the boards do not stop all egg hatching due to clutches laid on other pond surfaces (Gault et al. 2005).  The most effective method of removing Argulus spp. from recreational fisheries and aquaculture ponds is complete drainage and removal/restocking of fish, possibly combined with a treatment of lime, but this is not economically or physically possible in many cases (Gault et al. 2005; Taylor et al. 2006).

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 branchiurans. It should be noted that the effectiveness of these methods is likely significantly diminished against branchiuran ephippia.

Chemical
The compound organophosphate trichlorphon has been used to control argulids in ponds and aquaculture (Tonguthai 1997). Argulid adults and larvae fall off parasitized fish and die within 12-24 hours after treatments of 0.2-0.3 ppm, sprinkled or sprayed uniformly on the pond surface (Tonguthai 1997). However, argulid ephippia are not affected by organophosphate trichlorphon—multiple treatments must be applied over the hatching period for effective reduction.  In a study on chemotherapeutic control of ectoparasites in aquaculture, Singhal et al. (1986) found gammexane (1-6-hexachlorocyclohexane) to be most effective in removing Argulus indicus from host fish Indian carp (Catla catla), Rohu (Labeo rohita), Mrigal carp (Cirrhinus mrigala), grass carp (Ctenopharyngoden idella), and silver carp (Hypophthalmichthys molitrix) after a treatment was sprayed over the pond surface at 0.2 mg L-1 three times at weekly intervals. Placing Catla catla, L. rohita, and Ctenopharyngoden idella in 30 mg L-1 sodium chloride solution for 2-5 minutes was effective in removing A. indicus, and 1-2 minutes sufficed for H. molitrix and Cirrhinus mrigala (Singhal et al. 1986). Placement of fish in 0.5 mg L-1 potassium permanganate achieved 60% reduction of parasites within 5 minutes (Singhal et al. 1986). For severe infestations, 0.2 g L-1 of lime was used to treat drained, dried ponds, after which they were restocked (Singhal et al. 1986). Combinations of organophosphate pesticides and salt are reported to have controlled Argulus japonicus after four treatments at one week intervals (Avenant-Oldewage 2001). As with organophosphate trichlorphon, it should be assumed that the above treatments are ineffective against argulid ephippia, as the effects have only been studied on hatched branchiurans.

None of the above chemical control measures are effective under natural (unconfined) conditions. Attempting to control Argulus spp. using the above methods in natural settings would likely have severe financial implications and cause unpredictable ecological damage.

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