Relevance of the feeding ecology in invasive species management: prey variability in a novel invasive crab

Abstract

The diet composition of invasive species provides essential information to recognize potential impacts on an ecosystem. This study examined the feeding ecology of the novel invasive crab Cronius ruber from a demographic and seasonal perspectives. We identified 52 prey items in the gastric contents of the crabs (n=278), including more than 18% of the studied specimens that possessed empty guts. Preys with high frequency belonged to Brachyuran (51.54%) and Polychaete (34.36%), followed by Echinidea (22.47%), Gastropoda (21.15%) and Perciformes (20.70%). Additionally, observations during night sampling enriched the diet diversity of prey with missing stomach contents. Daily ingestion rates based on polychaeta indicate further prey consumption by juveniles and adults crabs than old adults. This was consistent with the number of prey retained per individual, changing seasonally and within ontogenic groups. Moreover, visual observation during night scientific-diving informs of native predators foraging on the invasive crab. These predators were groupers, octopus and elasmobranchs. Seasonally and ontogenically differences observed in diet through stomach content analysis and daily ingestion ratio may indicate that C. ruber has a generalist diet and dissimilarity analysis suggest a possible resource partitioning within ontogenic groups. The present results could represent the baseline for future studies on the possible impact sof this invasive NIS as well as part of the arguments to include C. ruber in the list of invasive alien species of European Union (EU) concern.