Invasive Species in USA Waterways - Part 33
The Louisiana Crawfish is an invasive species of freshwater arthropod. Native to Northern Mexico, South Eastern New Mexico through the Gulf States to Florida Panhandle and north through the Mississippi Basin to Southern Illinois and Ohio. Other names for the Red Swamp Crawfish include Red Swamp Crayfish, Louisiana Crayfish or Mudbug.
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 Louisiana Crawfish
Generally, dark red with elongated claws and head. While, having small or no spines on the side of the carapace just below the head. Further, have a triangular rostrum tapering anteriorly without a central keel.
Furthermore, has a linear to obliterate the dorsal surface between the two carapace plates, which converge. Meanwhile, rows of bright red bumps occur on the front and side margin and palm of the first walking leg (cheliped).
Generally, adults’ range in length from 2.2 inches to 4.7 inches. However, they may attain weights in excess of 50 grams.
In mature reproductive males there are hooks on the third segment of the third and fourth pairs of walking legs. The first swimmeret ends in four projections with the most anterior terminal end being a sperm transfer structure rounded with a sharp angle on the outer margin which lacks hairs at the tip.
While, there are setae on the anterior surface of the swimmeret closest to the terminal elements which have strong angular shoulders. Meanwhile, the right swimmeret is wrapped around the side, making it appear reduced or absent.
While, possessing a spur on the inner margin on the fifth joint. Furthermore, strong spines project from the inner face of the sixth joint. While, knots are present on the dorsal face of this joint.
However, the juveniles are not red and therefore difficult to distinguish from other juvenile species.
Biology of the Louisiana Crawfish
The Louisiana Crawfish has two types of behavior patterns. The one includes a wandering phase which involves short peaks of high speed of movement. While, the other is an immobile stage during which it hides in burrows by day and only comes out at dusk to forage.
Meanwhile, breeding male crawfish in the wandering phase may travel as far as 10.5 miles from the site of origin within four days. While, the nocturnal activity in the stationary phase does not appear to be driven by predatory avoidance or prey capture.
This species lives in a variety of freshwater habitats including rivers, lakes, ponds, streams, canals, seasonally flooded swamps and marshes. As well as, ditches with mud or sand bottoms and ample organic debris.
However, it frequently colonizes rice fields, irrigation channels and reservoirs. Able to tolerate a range of salinities up to 35ppt, pH levels, oxygen levels, pollution levels and temperatures. Provided that water in their burrows never freeze or exceed 203°F.
Though some species prefer water temperatures between 70°F and 86°F. However, prefers areas of lower flow velocity and low elevation. Further, establishing itself in warm, shallow natural and agricultural wetlands or small permanent ponds free from fish predation.
An ecosystem engineer, constructing simple two-crayfish burrows consisting of a single opening covered with a mug plug or chimney to reduce evaporative loss further from the water’s edge.
With the tunnel widening to an enlarged terminal chamber. Therefore, in periods of drought or elevated temperatures, the burrows extend 40 – 90cm down to the water table.
Fine sediments encourage deeper burrows than sand, gravel or cobble. Logs and vegetation encourage greater burrow density. While, water hyacinth has provided habitat for this crawfish in other introduced populations.
An opportunistic omnivore consuming plant material, animals, detritus and sediment. While, plants and detritus are consumed in greatest frequency and volume.
Meanwhile, the animal constituents of the Louisiana Crawfish diet include insects, crayfish, molluscs and fish.
Life cycles for crawfish are relatively short with sexual maturity in the species occurring in as few as two months. Breeding takes place in the fall, though in warmer and wetter regions there may be a second reproductive period in the spring.
Reproduces sexually. However, recent studies suggest it may also reproduce by parthenogenesis. High fertility rates and 10cm females can produce up to 500 eggs. While, smaller females produce around 100 eggs.
Egg production takes a period of six weeks, followed by a three-week period of incubation and maternal attachment. Followed by an additional eight-week period until egg maturation.
Females, incubating eggs or carrying young, may be found year-round contributing to their great success rate and the abundance of the species.
Optimal temperatures of 70°F to 80°F, allow for maximum growth while, temperature below 53°F inhibit growth. While, recently hatched crawfish remain in the burrow with their mothers and must molt twice before being self-sufficient.
Generally, adult crawfish live between two and five years.
The Louisiana Crawfish accounts for the largest majority of crayfish produced in the United States and elsewhere. With crayfish farming originating in Louisiana in the 18th century in rice fields as concurrent or alternate culture systems.
While, the concurrent culture of rice and crayfish makes good use of land, resources, equipment and infrastructure. Furthermore, crawfish are a good food source.
Generally, boiled in a large pot of heavy seasoning (salt, cayenne pepper, lemon, garlic and bay leaves) and other items such as potatoes and corn on the cob.
While, there are various different methods used to season the dish, there are equal number of opinions as to which is correct. However, generally served at a gathering known as a crawfish boil.
Distribution of the Louisiana Crawfish
The range of the Louisiana Crawfish includes the native range of Northern Mexico and far South Eastern New Mexico through the Gulf States to the Florida Panhandle. North through the Mississippi Basin to southern Illinois and Ohio. As well as, introduced countries in Asia, Africa, Europe and elsewhere in America.
Effect on the Ecosystem
The crawfish is a burrowing crayfish that can cause damage to water courses and crops, especially rice fields. While, the feeding habits can disrupt native ecosystems. Where it may outcompete native crayfish species. While, being a vector for the Crayfish Plague (Aphanomyces astaci).
As well as, several worms parasitic to vertebrates. Moreover, to humans, their burrowing habits may pose a threat to civil infrastructures such as storm ponds and levees. Therefore, resulting in economic loss.
Spread in the USA of the Louisiana Crawfish
The spread throughout the USA probably resulted from releases from aqua-culture or from the aquarium trade. Furthermore, is a popular live bait for largemouth bass and may have been thrown out of bait buckets. While, the Louisiana crawfish, could have been flushed down the toilet as they also occur in waste-water treatment areas.
Therefore, non-indigenous occurrences have been seen in Alaska, Arizona, California, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Maine, Maryland, Michigan, Minnesota, Mississippi, Missouri, Nebraska, Nevada, New Jersey, New Mexico, North Carolina, Ohio, Oklahoma, Oregon, South Carolina, Texas, Utah, Virginia, Washington and Wisconsin.
Conservation and management of the red swamp crawfish
The best management option for crawfish include catching and consuming crawfish. However, in Louisiana you required a license issued by the LDWF to commercially harvest wild crawfish.