Fluctuations in the population size of the highly endemic Aegla perobae (Decapoda: Anomura: Aeglidae) caused by a disturbance event

Abstract

During a two-year field study (July 2008-June 2010), we observed a sharp decrease in the number of the freshwater decapods, Aegla perobae, sampled monthly at the type locality. A series of population size estimates by means of the Schumacher and Eschmeyer mark-recapture method confirmed the decreasing trend of population size. Density dropped rapidly from 9.05 ind./m2 in April 2009 to a situation in which a reliable population size estimate was no longer possible due to the difficulty in retrieving marked individuals by February 2010. Results from additional estimations in 2011 and 2012 indicated that a slow and steady recovery phase of the population size has initiated. We present the hypothesis that the observed decrease in population size is due to an extraordinarily high precipitation episode during the 2007 reproductive period, which likely suppressed recruitment of the cohort produced in that year, with impact on the size-class structure and reproductive output of the population in the years that followed.