The marine protected area of Nha Trang Bay, Vietnam. Initial trends in resource status and utilization (2002-2005)

The marine protected area (MPA) of Nha Trang Bay, in eastern Vietnam, was created in 2002 as a pilot initiative to enable an adequate management of the fringing reef communities, while providing opportunities for alternative livelihoods to the local fisher populations. A reassessment of the data obtained during the baseline survey performed in 2002 and of an inventory performed in 2005 indicates a reasonable decline in faunal diversity and density in the MPA. Multivariate analyses of a great number of species suggest a cascading effect: a general negative trend in the richness of hard-corals at different depths is associated with an increase in macro-algal cover, and this links with a marked decline in the density of herbivorous fish. The reef of Hon Mun, a core zone at the hearth of the MPA and an attraction for underwater tourists, showed some recovery of the coral cover and density of other macroinvertebrates. Despite the loss in fish density, the structure of the fish food web seemed to remain unaltered. Reefs in the buffer area of Hon Mieu and Hon Mot showed, on the contrary, great declines in the faunal component and a clear increase in algal cover. These reefs are those most affected by human derived impacts, including urban run-off, shipping, silting, mariculture, fishing and tourism. The most distant reef analysed, at Hon Tre, although formally a core zone, is allegedly under strong fishing pressure owing to lack of surveillance enforcement. The major impact, so far, seems to be a marked decline in diversity and density of fish. Whilst the present data were collected during the initial stages of marine protection and need further replication, it is becoming evident that urban development and, particularly, fisheries and mariculture, which depend on great amounts of wild seed and feed collected in the area, may become antagonistic activities to the recovery of the reef to earlier states. Managers devising future management plans have now a base for re-scaling the size and zonation regime of the protected area, as well as that of adjacent industrial activities.