The Iraqi crab, Elamenopsis kempi in the Panama Canal: distribution, abundance and interactions with the exotic North American crab, Rhithropanopeus harrisii

We report on the distribution and abundance of the Iraqi crab Elamenopsis kempi in the Panama Canal and investigate possible interactions of this species with another invader, the North American mud crab, Rhithropanopeus harrisii. While more widespread than R. harrisii, E. kempi is currently limited to four locations within the Canal area: the Miraflores Lake, the Miraflores Spillway, the Southern Lagoon and the Northern Lagoon. Crabs reached peak abundances November through February. Where the two crab species overlap, the abundance of E. kempi was negatively associated with that of R. harrisii. Average E. kempi densities were significantly higher in cores with vegetation than those without vegetation. Laboratory experiments indicated that R. harrisii readily eats E. kempi, but that the presence of aquatic vegetation reduces predation rates. After four days, all E. kempi in treatments without vegetation were eaten, whereas only 53% of crabs were eaten in treatments with vegetation. Elamenopsis kempi is a small cryptic crab that can be easily overlooked even when abundant, suggesting that it may be more widespread than is currently reported.