Cannibalism as a potential factor affecting recruitment of the invasive Asian shore crab Hemigrapsus sanguineus

Abstract

Cannibalism affects the population dynamics of many marine species, but its potential for influencing population sizes of non-native species is not well understood. A series of laboratory experiments was conducted in 2016 to examine the frequency of cannibalism in the Asian shore crab (Hemigrapsus sanguineus) and the factors influencing its rates of occurrence. Predators and prey varied in size from planktonic megalopae (the last larval stage) and the first benthic crab stage to small juveniles (3-6 mm carapace width, CW), large juveniles (7-10 mm CW), and adult crabs (12-15 mm CW). Individual crabs were paired with groups of smaller prey in glass culture dishes with sand and rocks as potential shelter for the prey, both with and without an alternative food source (commercial crab pellets). Adult and large juvenile crabs consumed megalopae, first-stage crabs and small juveniles, regardless of the presence of food. Megalopae were cannibalized the most heavily, and the size difference between predator and prey was an important factor determining cannibalism rates. Cannibalism of settling megalopae and newly settled juveniles by larger conspecifics could affect recruitment to benthic populations of this non-native crab species.

Intertidal habitat complexity influences the density of the non-native crabHemigrapsus sanguineus

“…This species is more tolerant of the presence of conspecifics than other crab species ( Hobbs, Cobb & Thornber, 2017 ), which is another factor that could contribute to high densities of this invader. While small, newly-recruited juveniles might be subject to cannibalism ( Baillie & Grabowski, 2019 ; Crane & O’Connor, 2021 ), those that survive and grow to larger sizes can coexist under crowded conditions.…”

Effects of season and latitude on the diet quality of the invasive Asian shore crab Hemigrapsus sanguineus

“…Due to the relationship between diet quality, energy intake and storage, and population density, habitats with more available animal prey may be able to support higher Asian shore crab population densities (Forbes et al 2014). However, this expectation may be complicated by other factors, such as differences in planktonic larval settlement (O'Connor 1993) or increased predation on smaller conspecifics with in creased recruitment (Crane & O'Connor 2021). Regardless, a decline in diet quality during the reproductive season at certain locations could be a contributing factor to recent decreases in Asian shore crab popu lation densities, such as those reported at sites in Massachusetts (O'Connor 2018, Bloch et al 2019).…”