Spread of the green snail Turbo marmoratus in French Polynesia 45 years after its introduction and implications for fishery management

In 1967, 42 specimens of the green gastropod snail Turbo marmoratus (Linnaeus 1758) from Vanuatu were introduced in one single Tahiti reef, in French Polynesia. The population has been since protected to maximize its chance of spreading, to eventually provide an additional resource for local fishermen. After 45 years of natural dispersal and controlled transfers throughout Society, Tuamotu and Gambier Archipelago, we investigated the population status on 23 different islands and atolls. T. marmoratus failed to colonize Tuamotu and Gambier archipelagos, and Society western atolls. Conversely, it successfully established on the forereefs of all other Society islands and atolls. Densities were the highest on the windward side of Raiatea-Tahaa Islands, with up to 180 individuals per hectare. The observed densities and preliminary extrapolated stock for these two islands justify the rotational opening of the fishery, although additional local investigations on the biology of the species would be useful. The influence of this alien species on the ecology of local reefs remains unknown.