Spatial overlap and trophic interactions between a native commercial crab and the European green crab in Atlantic Patagonia

Abstract

The European green crab, Carcinus maenas, is a highly invasive species capable of exerting significant impacts onnative biota, particularly on species of ecological and/or economic importance. In Atlantic Patagonia, greencrabs have been rapidly expanding their distribution along the coast, yet their biotic interactions with native crabspecies have not been examined. Here, we investigate the agonistic interactions of invasive green crabs with thenative commercially important paddle crab (Ovalipes trimaculatus) in Atlantic Patagonia. This study determinedspatial overlap between both species and experimentally evaluated predator-prey interactions and competitionfor food. Our results indicate coexistence of Carcinus and Ovalipes trimaculatus in sandy bottoms of Nuevo Gulf,with green crabs being much more abundant than paddle crabs. Carcinus was present across all sampled locations,exhibiting highly variable abundances and considerable sex ratio disparity. In aquarium trials, mutualpredation only occurred between Carcinus and O. trimaculatus of contrasting sizes, although the time taken toobserve predation events significantly differed between both species, with green crabs displaying much highervoracity. Additionally, green crabs were the first to hoard food when it was offered. These findings suggest thatpredation by green crabs especially on juveniles paddle crabs may play a role in the decline of O. trimaculatus informerly abundant shallow areas in Nuevo Gulf. Thus, this study lays the groundwork for assessing interactionsbetween Carcinus and a broader range of native crab species, aiming to deepen our understanding of current andpotential interactions in the SW Atlantic.