Estimating population size of the red swamp crayfish (Procambarus clarkii) in fish-ponds (Brenne, Central France)

The red swamp crayfish, Procambarus clarkii, was discovered in 2007 in the Parc naturel regional (PNR) de la Brenne (France). Ten colonized sites have been identified in the park to date, including two new sites discovered in 2011. The present study aims at establishing a protocol suitable for estimating the population size of P. clarkii by the use of a Capture-Mark-Recapture (CMR) technique in a chain of five connected fish-ponds. Results show different cohorts of individuals among seasons and fish-ponds. However, trapping effort was not efficient enough to obtain an accurate estimate of the population size of this species in a fish-pond larger than 2-3 ha. On the other hand, the adopted protocol appeared useful to assess, in smaller fish-ponds, the effect of intensive trapping and other control methods on P. clarkii populations.