Injury, reproductive status, and distribution of Hemigrapsus sanguineus (De Haan, 1835) (Brachyura: Varunidae) on the rocky intertidal shores of Rhode Island, USA

Abstract

Intertidal crabs exhibit high occurrences of injury, including claw and leg loss. While it can be challenging to determine the specific cause of such injuries, the resulting distribution of injured individuals across habitat types is relatively easy to assess. We surveyed populations of crabs along Rhode Island, USA rocky intertidal shorelines to determine the distribution of injured vs uninjured individuals. We found that the invasive Asian shore crab Hemigrapsus sanguineus (De Haan, 1835) (Varunidae) dominated the surveys, with few other crab species found across our sites. There was little evidence for differences in the distribution of injuries across intertidal zones, with half of all crabs exhibiting loss of at least one limb. There were no differences in claw loss across the sampled populations, though mature crabs were 22% more likely than juveniles to be missing legs. Gravid females had the lowest frequency of injury of all crabs, being three times less likely to be injured than non-gravid females. Relative to other crabs, gravid females and juveniles were also less likely to be found in the high intertidal zone. Our results underscore the complexity of patterns of injury and resulting impact on demography, and help illuminate the role these patterns play in the ecology of intertidal animals.