26 May 2009

Are they a problem if people eat them?

Procambarus clarkiiA new report described in the Telegraph lists marbled crayfish as posing “high risk” to British wildlife if they are released into the wild.

This news story comes on the heels of two letters in the most recent issue of Science that offer a back and forth on the issue of introduced species. The first, by Gozan and Newton, talks about potential benefits of introduced species, like “aquaculture, sport fishing, forestry, horticulture, and game hunting.” The reply by Hulme and colleagues mentions crayfish as an example:

Major aquaculture species such as the crayfish Procambarus clarkii and Pacific cupped oyster Crassostrea gigas threaten endemic species through predation, competition, and/or the spread of diseases, and these two specific examples are widely recognized as some of the worst invasive species in the region(.) ... The history of biological invasions in Europe has too many examples of shortsighted decisions targeting perceived economic gains that have resulted in much larger (and often irreversible) costs to society. Thus, such “balance sheet” decision-making promoted by Gozlan and Newton, rather than a precautionary approach, is not only na├»ve but potentially dangerous.

This article on the National Science Foundation website has an related take on invasive species. It tracks students who were examining the impact of Louisiana red swamp crayfish (Procambarus clarkii) into China.

(W)e were surprised by how welcome this exotic crayfish was in the Chinese community, even among rice farmers whose crops were being destroyed. ...

Another rice farmer explained that if he had the necessary resources, he said he would sell only crayfish and eliminate rice farming all together.

Emphasis added. This is particularly relevant to Marmorkrebs, as it has been rumoured that they are being investigated for aquaculture purposes in China. Plus, asexual species in theory can generate double the number of reproductive offspring every generation compared to sexual species.

Thus, people could be extremely tempted to introduce Marmorkrebs into natural ecosystems deliberately. The problem is that such introductions have ended in tears as often, if not more often, than they have ended in triumph. (Two words: Cane toads.)

Harvested crayfish in Chinese fish market. Difficult to recognize, except for escapee in upper left!

22 May 2009

Jones and colleagues, 2009

Jones JPG, Rasamy JR, Harvey A, Toon A, Oidtmann B, Randrianarison MH, Raminosoa N & Ravoahangimalala OR. 2008. The perfect invader: a parthenogenic crayfish poses a new threat to Madagascar’s freshwater biodiversity. Biological Invasions 11(6): 1475-1482.


In 2007 an unusual crayfish found in food markets in the capital of Madagascar was preliminarily identified as Procambarus ‘Marmorkrebs’: a new world taxa and the only decapod known to reproduce by parthenogenesis. We present information on the identity, distribution and ecology of this recent invader and attempt to evaluate the threat it poses to Madagascar’s biodiversity and to livelihoods. The species appears to be currently limited to the area close to Antananarivo, but is being sold alive on major transport routes. We present molecular evidence of its taxonomic relationships and confirm that the Procambarus present in Madagascar is indeed the parthenogenic taxa. We investigate its reproductive ecology and find Procambarus ‘Marmorkrebs’ to have an extremely high fecundity; more than six times that of the native crayfish Astacoides. The limited evidence we have suggests that this species poses a serious threat to freshwater biodiversity and that it is likely to damage human livelihoods (through its impact on fishing and possibly rice agriculture). More research is urgently needed but in the meantime action is needed to reduce the rate of spread before it is too late.

Keywords: AphanomycesAstacoides • exotic • invasive species • marbled crayfish • Procambarus

19 May 2009


Marmorkrebs crayfish
Are parthenogenetic.
Males are not needed.

12 May 2009

In the newsletter

March issue of Crayfish NewsMarmorkrebs.org makes a brief cameo appearance in the latest Crayfish News newsletter with an article called, “Crayfish Blogging and Citizen Science.” The newsletter is a publication of the International Association of Astacology (password protected for members).

05 May 2009

How big is the pet trade?

In the new issue of Science, Smith and colleagues present some interesting information on import of wild animals.

Over half a million shipments of wildlife containing >1.48 billion live animals have been imported by the United States since 2000. ... The majority (92%) of imports were designated for commercial purposes, largely the pet trade.

Yup, that’s billion with a “b.”

The authors specifically comment on HR 669.

In its current form, H.R. 669 does not consider the economic benefits of wildlife trade. We argue that it should. H.R. 669 requires evaluation of the threat imported wildlife species pose as invasive species or carriers of known pathogens before importation. It proposes creation of lists of species “approved” or “unapproved” for import. Although the Act recognizes that there are species for which adequate scientific and commercial evidence is not yet available to make an evaluation of import risk, it does not stipulate how such species should be handled. For these species, we propose that H.R 669 should require their temporary placement on a “gray list.” These gray-listed species should receive priority funding for risk analysis.

Subcommittee hearings have been held, but no report has been made.


Smith KF, Behrens M, Schloegel LM, Marano N, Burgiel S, Daszak P. 2009. Reducing the risks of the wildlife trade. Science 324(5927): 594. doi: 10.1126/science.1174460