Population Structure and Dynamics of Hemigrapsus sanguineus Between 2008 and 2020

Abstract

An invasive species is one that is introduced into a new ecosystem. Through researching invasive species, we may begin to understand their impact on their introduced. Hemigrapsus sanguineus, known as the Asian Shore Crab, is an invasive crab species from the western Pacific region now found on the eastern seaboard of the United States. During low tide in September 2020, Hemigrapsus sanguineus were collected from the Read Wildlife Sanctuary site in Rye, New York. Samples were randomly collected by hand for thirty minutes per intertidal zone by removing them from below rocks. It was determined that there is a significant difference in carapace width between at least two of the three intertidal locations in 2020 and 2008, and that these population groups are not the same as 2020 appears larger (may be biased). Crabs closest to the water appear to have the highest egg mass, and intertidal location is inversely proportional to the average female egg mass. Egg mass between elevation groups has shown to be different. The 2020 data shows an increase in size of gravid crabs, which may be biased. The 2020 data contradicts previous research arguing that average density was higher in the high tidal zone than in the low tidal zone (Huston), and that gravid females are less likely to be found in the high intertidal zone (Hobbs et. al). The hypotheses that the species is seeing a decrease in size, and that the frequency of gravid females in the smallest reproductively mature classes would continue to increase were not supported. More research must be done to determine the differences and change in population density, as there was no difference in egg mass between elevation groups.