(b) Top-down treatments
The European green crab or shore crab, Carcinus maenas, which is native to Lough Hyne, was chosen as the top predator in the experiment. C. maenas exhibits very high abundance and a wide range in individual body size. It is an aggressively competing omnivore with a wide tolerance for many environmental factors [40]. This flexibility may reflect a special aptitude in adjusting individual growth, reproduction rate and population size structure gradually to temperature and other external stressors, as demonstrated for the similarly dominant Portunid blue crab, Callinectes sapidus [41]. Originating from Europe and North Africa, C. maenas has invaded rocky shores all over the world and threatens to outcompete many native species [40]. Hence, its ecological impacts on other species are of the utmost interest. Thus, C. maenas is a suitable experimental organism to simulate changes in population size structure as caused by warming.