Evaluation of sampling and analysis techniques for early detection of Limnoperna fortunei (Mytilidae) in limit areas of its distribution.

The golden mussel Limnoperna fortunei (Dunker, 1857) (Mytilidae) is an invading species in continental waters in the Neotropical Region. L. fortunei is transported by human activities. Differing from fresh water bivalves native to the region, this mytilid has external fertility and a planktonic larval development similar to marine mytilids (Monteiros-Ribas et al., 2006). The impact produced by L. fortunei on numerous South American rivers includes, among others, alteration of benthonic communities, alteration of fish diet, as well as severe macrofouling problems at industrial water intakes (Darrigran, 2002). Thus, it is fundamental to know the dynamic distribution of this invading species to explain its invading process and to have access to basic information to predict its distribution/ dispersion pattern. In the framework of a larger Project, in which we try to establish the extreme distribution limits of this species in South America, this work has as its goal to evaluate the efficiency of the sampling techniques of larvae and adults for the early detection of the invading species. For this purpose, sampling was carried out in different water bodies in limit areas of the species distribution in the endorreic system in the Province of Cordoba, Argentina. Between December 15 and 18, 2006, quantitative and qualitative samples of benthos and plankton were taken in eight localities looking for adults and larvae of the golden mussel (Table 1). Differing from sampling techniques in environments already invaded by the golden mussel where the aim is to know the population distribution of the settlement (e.g. Mansur et al., 2003), the goal of the sampling done in this work was early detection of the invading bivalve. The presence of adults of L. fortunei was determined by inspecting dredged-out submerged blocks (manually and with an Eckman type dredge) and by inspecting rocky exposures along the coast and on the riverbed. Detection of the larvae was