Predation transfers energy from a prey organism to a predator and generally increases the predator's survival or reproduction while reducing the prey's fitness, commonly through death. Its interaction signs are therefore (+,-), with the positive sign assigned to the predator and the negative sign to the prey. Reversing participant order would produce (-,+) without changing the biological relationship, so labels should always identify which species each sign represents. (-,-) characterizes competition, (+,+) mutualism, and (0,-) amensalism when the first participant is unaffected. Predation is
Ref:
Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 8-13