Biological control, as used in terrestrial systems, may hold promise f
or use against exotic marine species. We first review some marine pest
s, displaying their diversity, the damage they cause, and possible con
trols. We then contrast approaches for marine and terrestrial pest con
trol, providing guidelines for adapting terrestrial controls to the ma
rine environment. Although several of the same principles apply in ter
restrial and marine environments, marine systems differ with respect t
o the types of control agents available, the degree of pest-population
reduction needed for effective control, the spatial scale over which
biological control must operate effectively, the practicality of imple
mentation, and the nature and degree of concern over safety. As an exa
mple, we propose a strategy for developing a biological control progra
m against the European green crab, Carcinus maenas, which has had subs
tantial negative impacts where previously introduced (New England, Atl
antic Canada, South Africa, south Australia) and which has recently be
en introduced to central California, and to Tasmania. We conclude that
biological control may be possible for some marine pests, but that ex
isting strategies and expectations will require modification.