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   Gracilaria salicornia (alga)  français     
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         Management Information

    Once introduced, Gracilaria salicornia has the ability to spread within a site laterally and become locally dominant but have limited long range dispersal (i.e. between sites or islands, and evaluated over ca. 20 years) (Smith Hunter and Smith 2002). This suggests that management primarily can be applied on a site by site basis and with less effort on controlling between site spread.

    Results of herbivore preference tests, showed that several herbivorous fish species, including all of the species of acanthurids preferred (up to eight times more) native G. coronopifolia over alien G. salicornia. Although more work is needed to understand food preference of other grazers (such as sea urchins, crustaceans, mollusks, and turtles) these results suggest that enhancing fish stocks in invaded areas will not reduce alien algal populations (Smith et al. 2004).

    Experiments designed to investigate the use of salinity, temperature and algicides to control algal growth found that G. salicornia is resilient to all treatments except the chemical option (Smith et al. 2004). Chemical treatments showed the highest degree of mortality overall, with only samples in the low algicide treatments surviving.

    Manual removal of G. salicornia is currently the only feasible control strategy available. However, this technique is extremely time-consuming (6.9 hours per m² of substrate, significantly less for removing floating red algae unattached to substrate) and preliminary evidence suggests that G. salicornia will regrow rapidly. In addition, the removal activity itself generates fragments which are potential propagules and, therefore, care must be taken to avoid their dispersal.

    A diverse and multidisciplinary approach is needed when addressing management issues about invasive species in the marine environment (Smith Hunter and Smith 2002). For example management plans need to take into account the presence of marine protected areas or fisheries management areas and cycles of nutrient fluxes. français     



         Location Specific Management Information
    Kane'ohe Bay (Oahu Is.)
    Regrowth of Gracilaria occurred rapidly after an initial removal.
    Waikiki (Oahu Is.)
    Removal of unattached and drifting G. salicornia biomass from Waikiki was a first step for large-scale removal activities (Smith et al. 2004). A large group of volunteers was assembled to remove the floating fragments as well as the beach wash and were successful in removing a large amount of biomass of red algae from the reef and the trench. However they have yet to clear all of the drifting fragments. Smith et al. (2004) are currently in the process of designing an underwater suction device that they hope will help to speed up the process of removing drift algae.


         Management Resources/Links

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ISSG Landcare Research NBII IUCN University of Auckland