Here in Arizona ,the Game and Fish commission encourages catching as many crawdads as possible as they are illegally introduced and damage the aquatic environment. I just dont get it. As far as I know they hide under stuff during the day and are active at night and are primarily scavengers/garbage eaters. How does that damage the environment or is there something Im missing? Could it be they invade spawn beds of fish and munch on thier eggs? Why do these critters get such a bad rap?

They are omnivores, eating plants, animals like fish, insect larvae & nymphs, worms, as well as dead decaying stuff. Exotic crayfish can easily damage native species, but might not survive as well under tough conditions, resulting in a drastic loss of fish forage once the hardy species are gone. The wrong species can wipe out another species of plant or animal that's needed to complete the food chain.

Jim

I am inclined to agree with Jim. But I think that most of his remarks are based on a worst case scenario to say the least. But that being said it is a possiblitity. I wuld say that most of the uproar is created by ignorance and hysteria. I major in biology and at first glance I can't see how crawfish would have a major effect. I could be wrong though.

Peter

I have great respect for state game and fish departments.  They are usually very pro sportsman.  If they say something is a problem.  Then I would trust that it probably is.

Anything specie that isn't introduced to it's environment  by nature comes with the risks of unbalancing a food chain.  Much like Jim said but the reasons are countless.  Forage, disease, over and under population,etc.

There may very well be places in the country that could use more of them but according to your DNR, your state AIN'T one of 'em!   Any Marine biologists out there?

Catch those crawdads, hook them through the back and toss them out with no weight.  They will often get bit on the way down.  Let them hit bottom and reel in slowly.  You will run out of crawdads!

When the usual food supply begins to falter crayfish will feed on other crayfish. Some exotics grow larger and are more aggressive, capable of wiping out native species. http://www.esajournals.org/esaonline/?request=get-abstract&issn=1051-0761&volume=009&issue=02&page=0678

One species can decimate a whole class year of smaller species before they ar able to fend for themselves. Normally the native species in a fishery are somewhat compatible, one species often eating what another passes up. Some exotic crayfish are known to feed on endangered fish the native species ignore. http://www.usgs.gov/invasive_species/plw/crayfish.html  Some are displacing native species for a host of reasons. "Exotic crayfish...  The rusty crayfish, Orconectes rusticus, is a large, aggressive species that is rapidly expanding its range in North America, displacing native crayfishes in the process...." http://www.inhs.uiuc.edu/annualreports/94_95/CBD.html

Jim

Great reply, thanks Jim