Previous work examining the effects of emersion, as associated with
seed transportation processes, have shown such stressors negatively
impact upon a mussel's physiological condition and byssus production. In this experiment, however, mussels
emersed for 48 h displayed no greater susceptibility to predation.
Other stressors, such as exposing mussels to varying concentrations of
partial pressure of carbon dioxide (pCO2), have also been shown not
to alter the size or quantity of mussels consumed by starfish.
In addition mussels from different sources
(sublittoral, littoral and seed from rope culture), which may be expected
to have differing shell morphologies and adductor muscle strengths,
have been shown to have comparable survival rates when exposed to
starfish, with feeding rates averaging one mussel per day. It may, therefore, be the case that predator–prey relationships
are more dependent on the recent history of the predator than
condition of the prey. This could be especially
important if starfish are transported along with mussel seed and are
equally affected by the stressors associated with this process. Mortality
of mussels is often greatest immediately after transportation and
seeding, however, and migration of starfish towards recently seeded
mussels and scallops has been noted in a number of fisheries resulting
in increased predation pressures at such points in the cultivation process. Thus the short-term
response to predators is of particular interest to mussel cultivators.
The effects of transportation stress on mussel physiology and behaviour
do not seem to affect the predatory success of A. rubens preying
on M. edulis, so that physiological condition is unlikely to influence
predator–prey relationships in commercial relaying operations