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Unidentified Crayfish - Pacifastacus leniusculus

Unidentified Crayfish - Pacifastacus leniusculus
Pescadero, CA/ Little Butano Creek at Butano State Park, San Mateo County, California, USA
September 1, 2013
Size: about 4 inches

Moved from ID Request.

Signal Crayfish
invasive in California.

Thank you
Hi, thank you for spending the time in identifying this crayfish.

From what we know, this is the first time the signal crayfish is recorded in Little Butano at Butano State Park. There is the intention to proceed with removal.

I would appreciate if you could give us a little more details about the process of identification--this could be a good educational project for some of our programs with kids. For example, what are the identifying characteristics for the signal crayfish vs. the native species of crayfish?

Thank you again for your big help!

on ID
I am not an expert, and you should certainly seek expert confirmation before beginning a removal program, but the overall smooth body, large claws, and bluish white marks at the base of the chelae suggest signal crayfish, and lack of tubercles on the claws seem to rule out Louisiana crayfish (commonly seen in the Bay Area, with thinner claws) and Orconectes species. For some comparisons, check out this PDF from Washington Dept. of Wildlife, and also this report on Northwest crayfish (Note P. leniusculus is native in Washington). Cheers!

this report
Sam, I'm only getting a blank page at the hot link labeled 'this report'.

Oops! typo.
I somehow added "" to the beginning of the URL. The correct URL for the above-mentioned report is

replacement species
So, the Bay area has lost it's only Crayfish which represented 40% of the biodiversity of the Western US. The Red Swamp Crayfish has infested Marin Co form the hits I got for Crayfish California.

Does anyone know what will happen if we removed the Pacific Northwest Signal Crayfish form the streams that flow to the ocean in Santa Cruz and San Mateo? I read the Red Swamp Crayfish would attack our amphibians, what threats do the Signal Crayfish pose verses, is it now a needed species, or would it's removal cause some other cascade extinction?

Hi Scott, looking at this conversation and at the conversation we are having at the same time with State Parks, I think what we really need to do is a review of the research available so far on this subject. It would be an interesting challenge for me to partake. Also, a good occasion to learn and organize something to share the knowledge.

Sams last link
I found the last link Sam provided for us to be the most informative of the bunch.

Somehow we now need to know what the Signal Crayfish's impact is on Herps in general since we have so many endangered species in this area. Maybe I missed it in his article, but their preferred food supplies would be an asset, plus if anyone else has even studied them in our area.

I'm good for posing questions... You Portia and Sam have skills and resources I wouldn't know what to do with.

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