Source: Lake Weeders Digest LLC New Hope, Minnesota

Rusty crayfish is an aggressive invasive species of fresh water fish and is native to some of the states such as Indiana, Ohio, Tennessee and Kentucky. But lately a large amount of crayfish has been found in the northern lakes and rivers which have in turn been causing some environmental problems. The presence of the rusty crayfish in the lakes and rivers is believed to have been resulted from the use of the rusty crayfish as bait by some of the fisherman form the surrounding areas. The rusty crayfish has a brown body along with a more robust claws and which is larger than the other native species of the crayfish. On average, it can measure up to 10 cm.

Rusty crayfish have been believed to spread to the waters of Ontario, Minnesota, New York, Wisconsin and others with the use of the fish by anglers for bait. They have also invaded the portions of Quetico Provincial Park, Lake Superior and its tributaries. In the southern region they are found in the Ottawa River Drainage, the Trent Severn waterway, eastern Toronto region, upper Mississippi drainage, Eramosa river near the Guelph area.

Due to the rapid spread of the rusty crayfish in the lakes and rivers of other regions, it is being considered as a threat to the ecosystems. One of the main reasons being considered for their unatural spread is the use of the rusty crayfish by the anglers as a bait. Once the crayfish is introduced to a lake or river, it causes displacement of the native crayfish as it is more aggressive species of the crayfish and can also result in the complete wipe out of the native species. The rusty crayfish can consume twice as much food as the native species because of its high metabolic rate and a ravenous appetite for the aquatic plants.

Rusty Cray Fish properly know as “Orconectes rusticus” also have the ability to destroy the aquatic plants by clipping them on the base and consuming them at an exponential rate. Some studies also show that they are less prone to the predators as they have larger claws and their self defence is also more effective compared to other species. Other damage that the rust crayfish results is in the reduction of the population of the other submissive fish species such as the sunfish as they are not able to protect their nesting habitats and this can also result in the extinction of some of the weaker species as they lose their offspring too quickly. Some research has also shown that the ability of the rusty crayfish to abolish the aquatic plants also results in the increase of its population as it destroys the ability of the growth of the sunfish which acts as the predator of the crayfish as the off springs are not able to feed on the aquatic plants. Another impact of the rusty crayfish is the native species being more vulnerable to the predator attack. the birds like to feed on the native species of the crayfish as they have a softer shell as compared to the rusty crayfish species and this also results in the reduction in the fish population and limit for the food source for the fish.

Once a rusty crayfish is introduced in a water body, its control is difficult as it can spread rapidly. It is important to prevent their spraed to other water bodies in order to prevent the extinction of other fish species. A way to prevent the spread of rusty crayfish is to limit their use to their native water bodies. In addition to that, care should be taken that the fish is not transported as bait to other water bodies. Regulations like prohibition if overland transportation of crayfish helps in the further spread of the rusty crayfish.

Identification of the crayfish can be a difficult task. Some of the general characteristics that are used to identify the rusty crayfish species are the robust and longer claws that eh other species. There ar e also dark rusty spots on either sides of the carapace. The claws of the rusty crayfish are greyish-green or reddish-brown and are comparatively smoother.

Prevention of the crayfish is vital for the preservation of the ecosystems. Immediate quarantine of the affected farms and water bodies should be done and without any delay once the presence of the rusty crayfish is identified. Some of the steps that are taken are the ban on recreation fishing in the restricted areas along with ban on movement of the people in and out of the restricted areas. There are some chemicals which might kill a selective crayfish but they are not that effective. Some researches show that the healthy restoration of sunfish and bass can be helpful in depleting the rusty crayfish as they act as predators to the said species.

Education of the anglers, bait dealers and crayfish trappers about the harmful effects of the rusty crayfish on the environment also goes ion long way in prevention of the spread of the harmful species of the crayfish in newer areas. The water should always be drained from the boat, bilge, live well before leaving any access point of the water. The unwanted bait should be disposed in the trash or land. The only positive impact can be the commercial harvesting of the crayfish for human consumption.

For more more information this and other invasive species found in Minnesota as well as other sates, contact The Weeders Digest at 877-224-4899