In the first experiment, to test for effects of mussel condition on the
predation rate of A. rubens on M. edulis, individual starfish from the
three size classes (small, medium and large) were presented with 15
mussels from one of the two size classes (small and large) that were either
stressed or unstressed. Thus, there were a total of 12 experimental
treatments, each replicated six times, yielding 72 experimental units
(mesocosms). To manipulate ‘stressed’ conditions, these mussels were
left emersed in a temperature control room at 8.6 °C (±0.01) for 48 h
prior to use, ensuring the stress applied to mussels was consistent
throughout the experimental period. The 48 h period of emersion was
chosen because the transportation of mussels from seed beds to ongrowing
plots, which typically takes this long, has been shown to have
a detrimental effect on the physiology and behaviour of M. edulis