We conducted short-term size-based predation (=cannibalism) experiments in which five smaller green crabs were placed in a laboratory mesocosm with a large adult green crab. Size ratios of large to small crabs were experimentally varied using adult crabs of three size classes and juvenile crabs as small as were available representing recent recruits. Adult crabs were starved for 48 hours prior to the trial. Alternate prey in the form of small clams were also available in the mesocosms. Experiments were run for 24 hours after which are remaining crabs were retrieved and remeasured. All crabs were collected from Seadrift Lagoon, CA. 

See Turner et al. (2016) Biological Invasions 18: 533-548 for additional methodological details:
Turner, B.C., de Rivera, C.E., Grosholz, E.D., & Ruiz, G.M. 2016. Assessing population increase as a possible outcome to management of invasive species. Biological Invasions, 18(2), pp 533–548. doi:10.1007/s10530-015-1026-9