O. rusticus is an aggressive species. It removes the native crayfish from their burrows by crayfish to crayfish competition, and increased predation. "O. rusticus have been shown to reduce aquatic plant abundance and species diversity which can be especially damaging in areas that are relatively unproductive such as the northern lakes. These aquatic plants are important for habitat for invertebrates, food for fish and ducks, shelter for young game fish, pinfish, or forage species of fish, nesting substrate for fish, and erosion control (by minimizing waves). Although other crayfish eat aquatic plants, O. rusticus eat even more because they have a higher metabolic rate and appetite." (from http://www.issg.org/database/species/ecology.asp?si=217 the invasive species database).

They are cannibalistic (and I have a link to a very ecological paper of a study done on the cannibalism rates in juveniles if you'd like to read it). Even though the link below says O. propinquus, it does mention O. rusticus.

Perhaps the events you noticed were during the peak predation time (in the case of the dead crayfish), and the crayfish at the pet store were probably getting along at the time you were there(that's my guess anyways). I wouldn't use that experience at the pet store as a given for the species. That is one instance (and an unnatural one at that).

O. rusticus does not appear to me to be a scavenger, but it looks like they are nocturnal. The reason why they are "successful" invasives are listed above. I don't like the term successful and invasive in the same sentence. It's just not right.

I have no experience with crayfish, but I did research all your questions. All but the invasive species database were from journal articles (science based- experience). Hope this helps.
The Effects of Gender and Density on the Rate of Cannibalism in Orconectes Propinquus


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Phishie
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