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Crayfish

Crayfish (also called crawfish and crawdads) occur throughout the region. There are many species, some of which are listed below. They are important food of fish, birds, and especially furbearing animals. They are intermediate hosts of certain parasites. They are significant indicators of geologic relations in watersheds. Their relative size is related to local nutritional conditions. The richer the area, the larger or more abundant the animals. The mix of species is likely to be expressive of important ecological conditions and gradients, that is, they will be found to correlate well with topics of interest in the ecosystem, especially how populations change as communities age and mature. They are scavengers. They are also called "shredders" and help breakup leaves and plant materials which are then used by smaller creatures and plants in the decomposition process.

They may be an organism like the land snails, beginning the vegetation breakdown process rapidly (shredding leaves and organic matter in streams), producing the large surface areas to which the bacteria, fungi, and algae attach, and providing the digestible particles eaten by large stream fauna. They typically forage at night, seeking shelter in the day. Then they go after habitats with food when there are no predators, but after shelter first when there are predators present.

There are situations in which some species invade and out-compete other species of crayfish.

In some areas some species can be considered "keystone" organisms for they remove algae mats, enabling other life forms to attach, feed, and function (Creed, 1994). The effects is, as expected, related to the density and size of the crayfish.

The following is a list of the crayfish now known for the area. There are few studies and more work is strongly recommended. Information about new, verified collections is welcome. Red color letters and numbers are being used to designate data from forms or from computations resulting from the work of The Trevey's software.

There are 14 (B) total crayfish species known for Virginia.

The total crayfish species or taxa likely to be found in your area is 3(A)

The relative crayfish richness score for your area is 0.23(A / (B-i))

Crayfish management has rarely been achieved. It includes

• paying special attention to the species which have specific faunal space requirements,
• providing organic matter for food (leaves, animal waste, offal, dogfood)
• reducing pollution
• providing substantial protection from predators and trampling (by cattle and recreationists)
• protecting them and their egg masses during breeding periods
• providing different size protective areas for different size adults (Casitas are used for lobsters)
• providing intensive management areas, for multi-purpose population peaks, by supplying fertilized leaf litter (a truck load at a stream edge and occasional slaughter-house bone waste)
• providing pools in streams and also an open canopy (daylighted stream pools) for algae for those algae-feeding species
• promoting studies of their distribution and biology,
• promote studies of ground tides and the possible relations of crayfish (and other organisms) to such a phenomenon
• encouraging photography and art work
• creating observation areas and devices for underwater and night viewing
• monitoring signs of furbearer feeding activity
• monitoring changes in the population and making adjustments in tactics if they are ineffective in increasing numbers, species, or sitings

In some areas crayfish are considered pests (lawns, etc.) but we encourage asking the question of whether any real damage is being done. If their effects are substantial, then call or write to The Trevey staff and arrangements will be made with a qualified agent to reduce the damage.

(Please do not dump bait crayfish in areas other than where they are caught. Great competition can exist and some species may be lost due to the competitors.)

The list of crayfish known from the area, from the information system of the Department of Game and Inland Fisheries, Richmond, is as follows (under development):

Common Name (if one exists)	Scientific Name
1.xxx	1a. aaa
2.yyy	2a. bbb
3.zzz	3a. ccc
4. Unidentified	4a. ddd

Notes

The North Carolina crayfish can now be seen. They are likely to be strongly related to Virginia species.

In the lab, crayfish can be fed Tetramin, TetraWerke, Melle, Germany, fish food daily.

Traps used include: Lodge et al. 1986. Long term dynamics of three crayfish species in Trout Lake, Wisconsin. Can. J. Fisheries and Aquatic Sciences 43:993-998.

Fruit-juice size cans have been used in streams. Baited and with a hardware wire cloth inverted funnel over the entrance, they seem effective.

See the extensive work of Robert J. DiStefano (Bob DiStefano ) on his plan for the Missouri Non-Cave Crayfish resource.

References

Creed, R.P., Jr. 1994. Direct and indirect effects of crayfish grazing in a stream community, Ecology 75 (7): 2091-2103

Hill, A.M. and D.M. Lodge. 1994. Diel changes in resource demand: competition and predation in species replacement among crayfish, Ecology 75(7):2118-2126

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This Web site is maintained by R. H. Giles, Jr.
Last revision January 17, 2000.