Prey selection in crustacean-eating fishes following the invasion of the Asian shore crab Hemigrapsus sanguineus in a marine temperate community

Abstract

The Asian shore crab Hemigrapsus sanguineus invaded the coast of Long Island Sound approximately twenty years ago and has become hyper-abundant and the most common crab species throughout the intertidal region. The success of the species is hypothesized to be due to reduced predation pressure in the invaded region. Recent observations document the expansion of H. sanguineus into shallow subtidal habitats (i.e., up to 5m depth and up to 180 crabs m−2 in some habitats) where it is more accessible to a diversity of crustacean-eating predators. The role that higher trophic level predators might play in controlling populations of invasive species has seldom been investigated in marine communities. Here we conducted a series of prey-preference experiments under laboratory conditions to determine whether crustacean-eating fishes prefer H. sanguineus rather than native crab species, and to provide insight into how predator size and habitat type influence prey preference. Small size-class predators exhibited a clear preference for H. sanguineus in paired offerings of the invader versus native crab species while paired offerings for large size-class fishes resulted in mixed findings. Small size class predators demonstrated no preference when prey were set in a range of sediment type treatments (i.e., sand, pebble, cobble), while paired offerings for large size class predators resulted in mixed findings. In general, the results from this study support our hypothesis that H. sanguineus is preyed upon preferentially by native crustacean-eating fishes but sediment type and predator size play an important role in determining that preference. Preference for the invasive crab over the native prey items in some settings suggests prey switching could occur in areas where the invader is abundant. We suggest that future field studies focus on the role that crustacean-eating fishes can play in biological control of invasive crab populations and how management of predators can influence the impact of invaders.