The term "Marine trophic index’ is the CBD’s name for the mean trophic level of fisheries landings [and one primary marine biodiversity indicator]. Trophic level measures the position of a species in a food web, starting with ‘producers’ (eg phytoplankton, plants) at level 0, and moving through primary consumers that eat primary producers (level 1) and secondary consumers that eat primary consumers (level 2), and so on. In marine fishes, the trophic levels vary from two to five (top predators).