Giant Crawdads

[denjac]

JEFFERSON CITY-One person’s dream can be another’s nightmare. The

Australian red-claw crayfish is a perfect example, with serious

implications for ecological damage to Missouri.

The Australian red-claw, Cherax quadricarinatus, sometimes is called

the “freshwater lobster,” because it grows much larger than most

crayfish, topping out at more than a pound. Under favorable conditions,

it can grow much more rapidly than crayfish native to Missouri, reaching

three-quarters of a pound in its first year of life.

Naturally, commercial crayfish growers are interested in a species with

that kind of growth potential. Actually, that is just the start. Equally

important to crayfish culturists are the red-claw’s ability to

tolerate a wide range of living conditions and spawn several times a

year. On top of that, Australian red-claws lack the burrowing habit that

makes some crayfish species difficult to maintain in man-made ponds with

earthen dams.

In short, the red-claw seems to be an aquaculturist’s dream. So it is

not surprising that the Missouri Department of Conservation receives

periodic inquiries from crayfish producers asking about the possibility

of importing the Australian species. Those calls send cold shivers up

Resource Scientist Bob DiStefano’s spine.

DiStefano’s experience with crayfish goes back to graduate research

into the effect of acid rain on North American species. His early work

for the Conservation Department included studies of the importance of

crayfish as food for smallmouth bass and other sport fish. He also is

active in the International Association of Astacology (IAA), a group

whose members include both scientists and commercial crayfish

culturists.

DiStefano says that crayfish form a tremendously important link in

Missouri’s aquatic food chain. They inhabit every watery habitat in

the state, from muddy Mississippi River bayous to pristine springs and

caves. In many habitats they are extremely abundant.

Crayfish will eat almost anything. One of their staple foods is

detritus - bits of leaves, dead insects and other organic debris that

settles to the bottom of lakes and streams. Crayfish are, in turn, eaten

by everything from bullfrogs to herons. They make up the overwhelming

majority of the diets of some predators, such as goggle-eye sunfish,

smallmouth bass and, in the warm months, river otters.

“The more than 30 crayfish species native to Missouri are a huge part

of the food chain that sustains our lakes and streams,” said

DiStefano. “Our studies showed that goggle-eye eat almost exclusively

medium-sized crayfish, hardly ever large ones. There is no telling what

would happen to fish populations if those native species disappeared and

were replaced by crayfish that grow too large for most fish to eat.”

DiStefano said there is reason for concern that red-claw crayfish could

replace native species if the Australian species was ever introduced

into Missouri waters.

“Their size is a concern,” he said. “In the crayfish world, size

is a very big factor in competition. Large crayfish usually displace

smaller ones. We are worried about our native crayfish fauna because

these Australian crayfish are so much bigger.”

Competition is not the only worrisome prospect for DiStefano. He says

the introduction of North American crayfish into Europe provides a

sobering case study in what can happen when people transplant crayfish

to new areas. A fungus carried by new world crayfish without ill effects

proved devastating to European species, decimating the native crayfish

fauna.

“We have very little idea what these Australian crayfish might carry

or what effect their parasites and diseases might have on our local

fauna. Based on the European situation, it is not unreasonable to think

that these Australian crayfish might carry some pathogen that could get

out into our environment and cause a lot of damage. It has been a huge

problem in Europe and a wake-up call to those of us who work with

crayfish.”

For instance, said DiStefano, the red-claw crayfish is known to carry a

1-inch parasitic flatworm. Whether this parasite might devastate

Missouri crayfish species is unknown.

He said Australian red-claw crayfish can survive out of water and often

move short distances overland to new habitats.

“I have a friend who is a crayfish biologist in Australia who raises

these crayfish,” says DiStefano. “He cautions me that they are

nearly impossible to contain in a culture situation, even indoors. He

says he would be very skeptical of anyone’s claim that they could

totally contain Australian red-claw crayfish in a culture situation

without a few of them escaping to the wild.”

DiStefano said the Conservation Department is not opposed to crayfish

culture. In fact, he routinely advises people on crayfish culture, and

has contacts in the crayfish culturing community both in Missouri and

worldwide through the IAA.

He said many international crayfish biologists and crayfish culturists

do not support the establishment of red-claw crayfish in the United

States until they are thoroughly researched. He said he is not aware of

any federal restrictions on importation of Australian crayfish, but the

Conservation Department is taking a cautious approach and trying to

keep them out of the state at this time.

The Wildlife Code of Missouri prohibits the importation or possession

of Australian crayfish. Only species on the Approved Aquatic Species

List may be cultured.

“I’m not sure if that will be forever,” said DiStefano, “or if

at some point, years down the road, these crayfish will be researched

well enough to convince us that they are not a potential threat.”

The Approved Aquatic Species List is available at

http://www.sos.mo.gov/adrules/csr/current/3csr/3c10-4.pdf. DiStefano

urged people who want to import crayfish or other aquatic plants or

animals into Missouri to contact the Conservation Department first.

Further information about invasive aquatic species is available at

www.protectyourwaters.net/.

-Jim Low-

[Invert Interest]

Hi. I am doing some research and investigation into the possible problems and benefits of raising the Australian Red Claw, or perhaps one of the other large Australian crayfish species. Im not a scientist, or scholar, so all please forgive the bad spellings on occasion. I am currently on SSI, and as my choices of fancy cuisine is rather limited on my income- I started looking into raising, for my own benefit and entertainment some of these very curious creatures. Some very interesting facts did pop up if i was to ever get permission to raise some, either in my own home, or a connecting greenhouse type situation-that may, or may not, make raising them difficult or cost prohibitive. Important to me is how/if my chosen species could survive in my neighborhood , causing harm, without human intervention. some of the facts that put my mind best at ease regarding the possibilities of Crawfish escapees: (I will use Red Claw as my example as it is the species most adaptable and most under commercial consideration) Missouri Climate: Death will occur at temps below 60 or above 90. growth and reproduction stops at more restrictive temperatures. Nonviable / Non Typical behavior for surviving a trek on land- Non Burrowing behavior.= open and vulnerable to our own natural crawfish predators-and anything that would be attracted to its movements. INTERESTING: gills that become dry enough to breath on land, can now no longer support life in the water. Red Claw may now live up to 3 wks above ground,save predation, but will drown. Hypothetical direct release in water: Temperature restrictions still apply: Death will occur on release depending on depth of water or season - Non burrowing behavior is Non Typical behavior for survival in Missouri waters, its coloring is also bold - attracting immediate attention to itself.The Australian species do not hibernate. Adaptations are VERY DIFFERENT for survival in temperate Australia or our own gulf coasts, than in the state of Missouri. It appears to me they would make a great project for sheltered aquaponics or home aquaria.. and any reasonable management in that direction can be easily inspected for safety, if needed.

[Bird Watcher]

I think that's what the Arkansas Fish farmer said right before he dumped some harmless Asian silver carp in his pond.

[Invert Interest]

One of countless examples of why doing ones homework, and working closely with local conservationists is IMPERATIVE. Case by Case considerations with focus on real, provable, facts/impacts of approved content of study (in my case the above Red Claw as stated in my original post, re reading is recommended for clarity of topic, i have to all the time, to stay on task XD), always aware that results of viability of said venture may prove unfavorable for actual implementation. thank you

[Phil Lilley]

Good luck in your venture.

[ness]

How do they taste?

[fishinwrench]

"Acid Rain". Now there's a media term I haven't heard in a long time...

How did we stop that.... or did we just quit hearing/talking about it?

OR are we simply calling it something else now? Is there a more PC word for it nowadays?

[Jerry Rapp]

"Acid Rain". Now there's a media term I haven't heard in a long time...

How did we stop that.... or did we just quit hearing/talking about it?

OR are we simply calling it something else now? Is there a more PC word for it nowadays?

how about swine flu? Ebola? Sometimes you hear what they want you to hear. Affordable Care Act? Global Warming anyone?

[Phil Lilley]

We have a person here who is seriously studying a subject that's relevant to this forum. Please don't hijack the thread.

[Jerry Rapp]

sorry Phil. As far as a 12 inch crawdad, it could sure make a difference in the food base. And if anyone would ever be given permission to grow them in the Ozarks would be a very bad thing. But since someone already mentioned them, I am guessing they are already here. A 12 inch craw would have a 6 inch tail which would probably taste better than lobster, especially if it came from clear, freshwater.