Invasive Species in USA Waterways - Part 32
The Virile Crayfish is an invasive species of crayfish. Native to the Eastern United States and South East Canada. The native range extends from New Hampshire and Maine, across the Midwest including much of the Mississippi River and tributaries. As far west as Colorado, south to Texas and North to Ontario, Canada.
Other names for the crayfish are Northern Crayfish, Eastern Crayfish, Lake Crayfish and Common Crawfish.
Invasive Species Definition
The definition of an invasive species is any species that is not native to our ecosystems and cause harm when introduced to the ecosystems. Furthermore, these may include amphibians, plants, insects, fish, fungus, bacteria and more. Impacts on the environment may cause economic loss or affect human health.
While, Invasive species tend to grow and reproduce quickly and spread aggressively with the potential to cause harm on the environment, economy or even human health. Therefore, given the label “invasive”.
Description of the Virile Crayfish
Adult crayfish grow to around 45 – 125mm. While, males are larger than females. While, the Virile crayfish are reddish brown or olive brown color. Often numerous yellows bumps occur on the head side of the abdomen and pinches.
The large chelipeds are blue with orange or orange-red tips. Furthermore, dark specks occur on the pinchers. While, paired black blotches run along the abdomen.
Especially, prominent in younger individuals that have recently molted.
Biology of the Virile Crayfish
Capable of tolerating temperatures between 32°F and 90°F. While, preferring water temperature between 75°F and 77°F. With locomotion slowed or stopped at temperatures below 50°F. Therefore, resulting in dormancy.
The Virile Crayfish hide from predators under stones in lakes, streams and wetlands. While, the crayfish prefer streams with moderate water flow and turbidity with rocky sediment.
Where there is abundant cover and stable water levels. Often use rocks, logs and other organic debris as cover. Meanwhile, they occasionally dig pits in riverbanks and under rocks especially when water levels are low.
Omnivores with a wide dietary range. Including live and dead animals and plant materials. While, consuming macro-invertebrates such as snails and insects. As well as, small fish, fish eggs and tadpoles.
However, majority of the crayfishes nutrition comes from scavenging dead animals.
Breeding begins in the fall and continues to early spring. Extending until the adults retreat to deep waters and become inactive. While, breeding sometimes occurs for a brief period in the spring when water temperatures warm.
However, females store sperm for up to months and fertilize their eggs in the spring. While, attaching eggs to their tails in large balls resembling raspberries. Hatching takes one to two months from laying.
While, young hatchlings resemble their parents in miniature form. They can grow up to about 2 – 3cm long by the fall.
Virile crayfish live up to 3 years. Undergoing several molts in the first few months. However, they typically reach 23 – 56mm in their first year and 58 – 84mm in their second year.
Generally, reaching maturity during their second summer, around 24mm.
Uses of the Common Crawfish
The Virile Crayfish are used as fishing bait and for food for humans. As well as, as an aquarium food for carnivorous fish. A popularly consumed food in the United States with increasing popularity in Europe.
Distribution of the Virile Crayfish
Occurs in Southern Canada from Alberta to Quebec and in the Northern United States. However, has become invasive in some parts of Northern America, outside the native range. Furthermore, discovered in the United Kingdom.
Effect on the Ecosystem
The Virile Crayfish have many negative effects on the ecosystem. Drastically decreasing some macrophyte populations and macro-invertebrate communities. Further, displacing native crayfish, such as the endangered Pacifastacus nigrescens, Orconectes obscurus, Cambarus bartonii, Orconectes limosus and Cambarus bartonii bartonii.
Furthermore, causing declines in the Chiricahua Leopard Frog (Rana chiricahuensis), Three Forks Spring Snail (Pyrgulopsis trivialis), Canadian Native Snails such as Stagnicola elodes and Physa gyrina. As well as, a decline in other snails and invertebrates.
As well as, causing a decline in fish species, including the desert suckers (Catostomus clarkii), Sonora Sucker (Catostomus insignis), Speckled Dace (Rhinichthys osculus), Little Colorado Spinedace (Lepidomeda vittata), Flannelmouth Sucker (Catostomus latipinnis) and White Sands Pupfish (Cyprinodon Tularosa). While, further consuming fish eggs leading to a reduction in populations of the sunfish, bluegill and trout.
Meanwhile, these fish carry diseases that they spread to other. Including the White Spot Syndrome Virus from shrimps which was found to be highly pathogenic and readily passed on to the crayfish by their cannibalistic behavior. While, having one of the highest infestation rates of the Crayfish Plague found in the United Kingdom.
Furthermore, alterations of structures and composition of littoral zones. Causing an increase in turbidity of waters and impacts to irrigation networks and levees as a result of their burrowing habits. Therefore, causing economic impacts to humans such as damages to riverbanks and flood fences.
Introductions of the Virile Crayfish
The use of Virile Crayfish as a live bait could possibly be a main reason of non-native spread of the crayfish. While, invasive species in Alabama, Arizona, California, Colorado, Connecticut, District of Columbia, Idaho, Illinois, Kansas, Kentucky, Maine, Maryland and Massachusetts.
As well as, Mississippi, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia and Wyoming.
Deliberately introduced to France in 1897 and Sweden in 1960s. However, these attempts were unsuccessful. Currently, occurs in the Netherlands and the United Kingdom. Where introduction was via the aquarium trade in 2004.
Management of the Common Crawfish
Pesticides and chemical controls should only be used according to the national list of relevant authorities determined by country and state. Governments of Canada and the United States have banned the use of live crayfish as bait, which has ben a main cause of spread.
While, public awareness of the non-native invasive crayfish between regions and countries varies considerably. Therefore, where possible, water users should be educated, especially recreational anglers who can play a role in introductions and detections of populations.
However, there is currently no known sanctioned methods for eradication of crayfish populations in place. While, biocide and trapping have been attempted, reducing numbers but not capable of eradicating the virile crayfish. Therefore, due to the difficulty in eradicating populations, inter-regional movement and spread must be reduced.