| The crustacean Cherax quadricarinatus (redclaw), a crayfish from Australia that is widely cultured, was introduced illegally into Puerto Rico in the beginning of 1997. They escaped from a single culture facility at the headwaters of the Loiza River in 1998 during Hurricane Georges and subsequently were found in the Loiza River and later in the Lajas Valley, where they had been transferred for experimental purposes. The Bayamon River (Cidra reservoir), Espiritu Santo River, Lajas Drainage Canal and Loiza River systems were sampled quarterly for one year, to establish the range within Puerto Rico's streams to evaluate the crayfish population and determine its preferred habitat. The Arecibo, Blanco, La Plata, and Rio Piedras rivers were sampled at least once to determine the presence of redclaw. Five 6-mm mesh cylindrical traps were used to catch redclaw and other organisms. Mean redclaw catch per unit of effort (CPUE) in 12 hours was 1.85, 1.60, and 1.45 in Loiza, Carite and Cidra reservoirs, respectively; and 1.0, 1.35, and 0.55 in the Lajas Drainage Canal, and Loiza reservoir headwaters (Gurabo and Loiza Rivers), respectively. No redclaw were captured below dams (tailwaters) of the Cidra and Loiza reservoirs, and no redclaw were captured in the Espiritu Santo River system. Positive correlations (species correlation with variable) were found for Macrobrachium acanthurus /pH (r= 0.651), Macrobrachium faustinum/pH (r= 0.857), M. acanthurus/DO (r= 0.831), Macrobrachium carcinus/turbidity (r= 0.744); negative correlations were found for redclaw/DO (r=-0.419), Epilobocera sinuatifrons/discharge (r=-0.447), E. sinuatifrons /temperature (r=-0.766), redclaw/M. acanthurus (r=-0.522), redclaw/M. carcinus (r=-484), redclaw/Xiphocaris elongata (r=-0.463). There were more than 24 aquatic exotic species trapped during the study. Thus, redclaw is established in Puerto Rico. Slow-moving waters, including reservoirs and canals, and with muddy or silty bottoms were redclaw habitats. Assuming a constant rate of dispersion of redclaw of 0.5 river systems each year, 5 additional river systems would become theoretically inhabited by redclaw within the next ten years. Redclaw cause no evident environmental damage (though specific studies regarding their potential ecological impact are needed), and are being exploited as a food organism by an unknown number of local fishermen. |
