Green Crab (Carcinus maenas) Foraging Efficiency Reduced by Fast Flows

Abstract

Predators can strongly influence prey populations and the structure and function of ecosystems, but these effects can be modified by environmental stress. For example, fluid velocity and turbulence can alter the impact of predators by limiting their environmental range and altering their foraging ability. We investigated how hydrodynamics affected the foraging behavior of the green crab (Carcinus maenas), which is invading marine habitats throughout the world. High flow velocities are known to reduce green crab predation rates and our study sought to identify the mechanisms by which flow affects green crabs. We performed a series of experiments with green crabs to determine: 1) if their ability to find prey was altered by flow in the field, 2) how flow velocity influenced their foraging efficiency, and 3) how flow velocity affected their handling time of prey. In a field study, we caught significantly fewer crabs in baited traps at sites with fast versus slow flows even though crabs were more abundant in high flow areas. This finding suggests that higher velocity flows impair the ability of green crabs to locate prey. In laboratory flume assays, green crabs foraged less efficiently when flow velocity was increased. Moreover, green crabs required significantly more time to consume prey in high velocity flows. Our data indicate that flow can impose significant chemosensory and physical constraints on green crabs. Hence, hydrodynamics may strongly influence the role that green crabs and other predators play in rocky intertidal communities.

Water motion modulates predator nonconsumptive limitation of prey recruitment

“…), as such conditions decrease the ability of mobile organisms (such as barnacle larvae) to locate cue sources (Ferner and Weissburg , Robinson et al. ). However, high water flow also favors the supply of barnacle larvae to the intertidal zone (Bertness et al.…”

Keystone predation and molecules of keystone significance

“…Intense turbulent mixing rapidly dilutes dissolved chemical concentrations and creates extreme variation in the spatial and temporal distributions of waterborne cues (Weissburg and Zimmer-Faust 1993, Zimmer and Butman 2000, Crimaldi et al 2002. Under such demanding conditions, submerged predators are unable to navigate successfully in finding prey via metabolite plumes (Jackson et al 2007, Robinson et al 2011. Biotic interactions on wave-swept shores thus depend as much or moreon surface chemistry as opposed to alternative types of sensory stimuli (Feder and Lasker 1964, Lubbock 1980, Palmer et al 1982, Boxshall 2000, Steinberg et al 2002, Dreanno et al 2006).…”

Disturbed flow in an aquatic environment may create a sensory refuge for aggregated prey

“…Either mechanism would act to make tracking the cue to the source more difficult for the predator (Robinson, Smee & Trussell, 2011), although this may depend on the predator’s sensing strategy and sensitivity (Ferner & Weissburg, 2005). Our observations with food dye suggest that the plume in disturbed flow split primarily into two meandering plumes.…”