Nha Trang Bay marine protected area was establishted in 2002 as a pilot initiative to enable adequate management of the reef communities, while providing opportunities for alternative income to the local community. A re-assessment of the data obtained during the baseline survey performed in 2002 and of an inventory performed in 2005 indicates a reasonable decline in hard coral structure in the marine protected area. The reef of Hon Mun, a core zone at the hearth of the marine protected area and an attraction for underwater tourists, showed some recovery of the coral cover. Reefs in the buffer area of Hon Mieu and Hon Mot showed, on the contrary, great declines in the coral cover and abundance. These reefs are those most affected by human derived impacts, including urban run-off, mariculture, fishing, tourism, etc. The most distant reef, 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 change in coral cover and species, especially in the deeper area. Despite the lack of data replication in the present work, it is becoming evident that coastal 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 now have a base for re-consideration regime of adjacent industrial activities.
The Nha Trang Bay’s biodiversity was high, with 350 species of reef building corals, 220 species of demersal fish, 160 species of mollusks, 18 species of echinoderms, 62 species of algae and seagrass (Tuan et al., 2002). This showed the highest marine biodiversity as yet known from Vietnamese coastal waters, and indicated that the marine protected area (MPA) shares strong biogeographic affinities with neighboring nations and the Indo-West Pacific center of diversity (Tuan et al., 2005). Moreover, due to a high abundance of larvae, this water area is being considered as a major nursery ground to supplement fish larvae to other coral reefs of Vietnam and maybe Cambodia (Wilkinson, 2000).
Marine biodiversity suffers threats from a range of direct human activities, increase in global temperature and unpredictable changes of weather (Bryant et al., 1998; Veron, 2000). Destructive fishing and over-exploitation to meet the people’s demand for seafood, as well as the aquaculture and tourism industry for outsiders, depleted a large part of coral reefs in Nha Trang Bay. Until 2002, many species of reef fish, sharks, mollusks, crustaceans, and particularly targeted species were decreasingly found, or locally extinct. Some commercially targeted groups had been in poor condition for more than one decade (Cheung and Tuan, 1993).
Recognizing its important biodiversity values and increasing pressures placed upon the marine area by human use, the Government established the first comprehensive MPA of Vietnam in the Hon Mun region in 2002 (IUCN Vietnam program, 2001) with the objectives: “to enable local island communities to improve their livelihoods and, in partnership with other stakeholders, effectively protect and sustainably manage the marine biodiversity at Hon Mun as a model for collaborative MPA management in Viet Nam.”
Research rationale and objective
Nha Trang Bay MPA was established in 2002 with wide purposes. To achieve unambiguous goals however, specific and measurable objectives must be defined in terms of what outputs and outcomes are being sought. This in turn requires that well-defined management plans be developed, measures of MPA success identified, impacts of management actions be monitored and evaluated, and that results of these activities be fed back into the planning process, to revise objectives, plans and outcomes. In other words, MPAs need to be adaptively managed.
In the period of 2002–2005 a considerable amount of information was collected in the area using biodiversity measurements and surveys on the status of human activities were conducted yearly. Unfortunately, the biological information collected had not been thoroughly analyzed, nor had any attempts been made to associate ecological trends with management strategies or the development of the fishery, aquaculture and tourism industries (Tuan et al., 2005; Dinh et al., 2005a, 2005b; Nga et al., 2002a, 2002b, 2002c). This report aims to answer some practical questions: Can we measure changes in hard coral species abundance and community from 2002 to 2005? Can specific human activities be linked to specific developments in reef communities? Can we relate changes in tourism, aquaculture and/or harvesting intensity to changes in diversity in MPA?
Material and methods
Hard coral community
The secondary data on hard coral community in the present work were collected from the report “Biodiversity of the Nha Trang Bay MPA, Khanh Hoa, Vietnam, reassessment 2002–2005 by Tuan et al. (Tuan et al., 2005). This report was the result of survey programs that were performed regularly in August 2002, as part of the implementation phase of the MPA pilot project, and re-conducted in March-April 2005.
Using Rapid Ecological Assessment (REA), the researchers of Nha Trang Institute of Oceanography surveyed fish assemblage at four key locations, with broad geographic spread across the MPA and representative of the different coral communities and zoning scheme: southwest Hon Mun within the core zone, and southwest Hon Mot, north Hon Mieu and east Hon Tre within the buffer zone. In the field, two depth contours were surveyed independently at each site, including a deep slope (20m–8m) and shallow slope (7m–2m). Each specialist diver swam slowly and recorded all species and their abundance categories within 250 m2, on waterproof paper on a clipboard. At the end of each dive, the taxonomy inventory was reviewed, and each species was ranked in terms of its relative abundance in the community: 0 = absent; 1 = rare; 2 = uncommon; 3 = common; 4 = abundant and 5 = dominant.
Primary data on tourism, aquaculture and marine fishing within the MPA were collected from scientific and annual technical reports of Hon Mun Authority, Khanh Hoa province departments. To fill in some of the gaps of information and to obtain updates of the trends in human activities, a new rapid survey was conducted in July 2006 for the present work. This information was obtained during un-structured interviews to divers, fish farmers, fishers and researcher who envolved in the MPA. The main questions in these conversations were concerned the present status of the enterprise, expected future trends and links to tourism, and stakeholder’s perception about reciprocal influence of human activities and MPA.
Multivariate techniques were instrumental to search for patterns in community data and were used to detect changes to fish assemblage in this study (Krebs, 1989). Multivariate ordination of observations with linear or uni-modal techniques allows an arrangement of species and environmental variables in a plane defined by two orthogonal (x-y) axes. The choice of multivariate method of analysis depends to a large extent on the nature of the data and secondarily on the length of the statistical gradients (Ter Braak and Smilauer, 2002). The present inventory observations consisted originally of categorical data. Hence, uni-modal techniques of the Correspondence Analysis (CA) and Canonical Correspondence Analysis (CCA) were used in the present study. Statistical testing of the importance of environmental variables is also possible in CANOCO using Monte Carlo permutation tests for example (Ter Braak and Smilauer, 2002).
The statistical package Cano Draw 4.5 was used to analyze graphically the combination of sample and species observations, as well as their association to environmental and supplementary environmental variables (Ter Braak and Smilauer, 2002). Samples and variables were displayed on the same ordination charts in a form of point-arrow biplots or triplots. In CCA, sites are at the centroids of species: the site found near the point representing the centroid of a qualitative explanatory variable is more likely to possess the state ‘1’ (or high score) for that variable. Site points that are close to one another are likely to be relatively similar in their species relative frequencies. When species are the goal of interpretation, a species found near the centroid of a qualitative explanatory variable is likely to be found frequently or in larger abundances in the sites possessing the state ‘1’ for that variable. Species points that are close to one another are likely to have relatively similar relative frequencies in the sites (Borcard, 2004).
There was a dramatic increase in the number of cages and in the total culture area, from 1,675 cages in 2001 to 5,096 cages in 2004, an increase of nearly 204% in 3 years (Kinh et al., 2004). About 30.1% of the families within the MPA engaged in lobster cultivation with an average of 2.5 cages per family. This contributed to a significant part of the total yearly income, accounting for 54% of total household income (Thu, 2005).
The main culture sites in Nha Trang Bay MPA are Vung Me, Tri Nguyen, and to a lesser extent Hon Mot, Dam Bay, Bich Dam and Vung Ngan. Due to the construction of the VinPearl resort, and other tourism expansions in SW and N Hon Tre, most of culture cages located at Vung Me have been moved to other areas. Owning to their geographical distribution, the areas and sites used for biodiversity assessment may correspond to different levels of impacts from aquaculture. The station of N Hon Mieu is the nearest to a city and port, therefore, in more close exposure to pollution from the shipping traffic and land run-off. N Hon Mieu is also the most affected by aquaculture from Tri Nguyen; the site of SW Hon Mot is the closest to the extensive culture area (Vung Ngan) and may be impacted by the organic load resulting from waste or uneaten fishfeed. The food conversion rate is low, about 1/20–1/25 for lobster and 1/6–1/10 for grouper. Consequently, an estimated total of 6,650 tons ‘trash fish’ has been annually used for lobster culture (Kinh et al., 2004; Tung, 2002). The other areas, SW Hon Mun and E Hon Tre seem to be far from culture zones, and thus may have suffered less from aquaculture-related activities.
Attempts have been made to raise lobster from artificial seed, so far with only limited success (Tung, 2002). Hence, current aquaculture practices rely solely on wild-caught seed-stocks. Rapid development of lobster and marine fish cultures has dramatically increased the demand for seed. For example, total lobster seed demand in Hon Mot increased from 400 individuals in 1997 to 17.000 individuals in 2001 (Nga et al., 2002a, 2002b, 2002c). According to the farmers interviewed, seeds can be obtained several ways: (1) Seeds are bought directly from fishermen. If their size is small as ‘a bamboo toothpick’ they are nursed with a high density in nursing cages till they reach the expected size. Then they are released into cages or floating rafts for commercial grow-out; (2) Using fishing gears, farmers collect seed themselves; (3) Professional seed collectors operate inside or outside the MPA, using mainly hookah diving or trawls, and then sell them to households.
Seed nursing was more common before. But depletion of the native seed, along with a low survival rate in nursing caused by the water pollution, has led to an increasing reliance on the purchase of seeds from professional seed collectors in recent times. Most households had difficulties to precisely quantify the different sources of their seeds. But, the majority stated that they preferred the native seed that had been supplied directly by fishers or collected by themselves due to higher quality and lower price.
There were about 380 and 527 motorized fishing boats in the MPA in 2002 and 2005, respectively, with an average of 200 fishing days per year per boat. Most of them were small boats with the length from 5 to 14.2 m, and horsepower capacity mainly from 6–80 Hp. However, there are strong suspicions that the total number of fishing boats was underestimated: it is not known how many boats of outsiders are presently operating inside the MPA. With regard to the employment status of fishers 46% of them own their boats, while the remaining 54% work as hired crew members (Dinh et al., 2005a; Tung, 2002). Approximately 3,797 tons of fish and 84,573 individuals of lobster seed were caught in 2003 (Dinh et al., 2003). Fishing within the MPA is characterized by a diversity of gears and species, but is mostly small-scale in size (Dinh et al., 2005b). A total of eleven main fishing gears are being operated within the MPA. Although regulations on fishing management within the MPA water zone came into effect in 2002, poison and blast fishing were still conducted illegally by several divers and poor fishers in 2003 (Dinh et al., 2003). These illegal fishing practices were, however, not detected in the monitoring programme in 2005 (Dinh et al., 2005a, 2005b).
Owing to the different grid utilized to gather information on fishing activities it is difficult to match exactly fishing areas to the surveyed stations for bio-diversity. But, Hon Mieu locates within fishing zone I, Hon Tre in fishing zone III, and both Hon Mot and Hon Mun fall coarsely into fishing zone IV. As stated by some MPA researchers during the interviews the core zones of the MPA seem to be too narrow, and even these areas are probably largely affected by the fishing activities taking place in adjacent waters. The station of E Hon Tre is far from the land and, seems to be the one more greatly impacted by fishing at present.
39 major fish families were caught by nine fishing gears within MPA, in 2005. Among the 34 families that were recorded in biodiversity assessment programs in 2002 and 2005, 17 families were listed as commercially exploited in 2005. There were some changes in catch per unit effort (CPUE) of insider-fishing boats during the two fishing seasons, but all changes could not be understood clearly. For example, in northeast monsoon season (October to March), CPUE of purse seine and stick-held dip nets increased dramatically from 2003 to 2005, from 5.15 to 39.26 kg hour−1 and from 12.19 to 16.93 kg hour−1, respectively (Dinh et al., 2003, 2005a, 2005b).
The two prevalent models of tourism in Nha Trang Bay are the island tour and the sea tour. Island tourism occurs when visitors go to the expected places by boat and then visit the island on foot. Contrastingly, the sea tourism happens when tourists travel by boat and stop for sea bathing, swimming, diving and other relaxed activities in the sea. The most common places for island tourism are Tri Nguyen, Hon Tam, north Hon Tre and Hon Mun. Diving takes mostly place at Hon Mun, and to a lesser extent at Hon Tam, Hon Noc, Hon Mot and Bai Lan. Swimming, with or without snorkelling gear, takes place mostly at Hon Mun, Hon Tam and Bai Lan. Northeast Hon Tam is the destination for sport activities such as jet-skiing, parasailing, and banana boating. Currently, over 100 tourism boats, powered by 50 HP engines and smaller speed boats are operated within the MPA. According to the statistical data for 2005 provided by the Cau Da Tourism Management Company, most visitors went to Tri Nguyen (< 55%), followed by Hon Tam (< 27%), Hon Mot and Hon Mun (< 18%).
The revenue of Nha Trang tourism was over US $41 million (equivalent to 643,738 million VND) in 2005, and contributed to 40.95% in Gross Domestic Product of the Khanh Hoa province. There was an annual increase in the number of visitors in terms of domestic and foreign ones after one decade (1995–2005), from 317,000 to 902,468 visitors (Khanh Hoa province., 2006). The number of divers has increased. Presently nine diving clubs have regular operation within the MPA water with about a total 100 divers per day and often serve approximately 9,800 dive trips annually. Most divers were foreigners, 13,500 foreigners compared with 4,500 Vietnamese divers (Michael et al., 2005). The survey carried out in 2006 shown that a total number of divers per diving club per day ranged from 7 to 22.
The different areas and stations utilized for the biodiversity assessment programme in 2002 and 2005 are differently influenced by tourism activities. North Hon Mieu lies closest to the city and port and is the most affected by general boat traffic. It may also have suffered most from island tour-related activities in Tri Nguyen; the station of SW Hon Mun is near to tourism centers and is frequently affected by divers, general sport activities, and swimmers; SW Hon Mot has a general frequency of divers and swimmers; E Hon Tre lies farthest from the continental shore and, hence, any kind of tourism activities are rare there.
Hard coral community
A total of 312 species of hard corals, belonging to 15 families and 60 genera, were found in total, but there were remarkable differences among the families. Acroporidae (98 spp.), Faviidae (66 spp.), Fungiidae (31 spp.) and Poritidae (29 spp.) were the dominant families, with high occurrence at all locations. Trachyphylliidae, Astrocoeniidae and Oculinidae were rare families with 1–2 species observed in each family. The total number of species of hard living corals found in the whole MPA slightly declined from 274 species in 2002 down to 256 species in 2005 (Table 1). There was a decline at N Hon Mieu (24.59%) and E Hon Tre (5.35%), and a slight increase at SW Hon Mot (15.87%) and SW Hon Mun (0.65%).
Hard coral structure
The CCA demonstrated a considerable association of the environmental variables area, year, and depth, with the distribution of hard living coral species. The variables area and year, as well as depth explained an important proportion of the overall variation in species-environment relationship, with cumulative percentages of 29.2% and 24% for axes 1 and 2, respectively. In general, the first two axes explained 27% of the variability in species data.
The scatter diagram resulting from the (CCA) ordination of hard coral species is shown in Figure 1. Owing to the large number of species represented, and for the sake of clarity, the environmental variables are omitted in this figure, but these are plotted again in Figure 2. Overall there was a clear and significant effect (P = 0.01) of time, and this reflects on the distribution of the species in relation to the 2002–2005 gradient, which is indicated by two opposing vectors in the diagram. Species that were more relevant in 2002 tend to be distributed on the northwestern part of the diagram, while those that gained expression in 2005 were more markedly represented on the southeastern part of the diagram. Less affected hard corals tended to take intermediate positions along this gradient, as e.g. the species belonging to two major families Acroporidae, Poritidae, which remained constant. With regard to spatial effects, the stations of SW Hon Mun, SW Hon Mot and N Hon Mieu normally clumped together on the upper left part of chart. Thus, they seemed to have similar patterns in species composition. These three stations differed markedly in species composition from the E Hon Tre station, which represented more abundant with species on the lower right part of the chart. Moreover, many rare species were found, but it was difficult to match their association to specific sites or years. Such was the case of 38 coral species that were only recorded in 2005, e.g. the corals Porites annae, Pocillopora danae, Lobophyllia flabelliformis, Fungia fralinae, Stylophora subseriata.
Monte Carlo permutation techniques were used to test the significance of the different environmental factors on hard coral species composition. Factors related to area, such as the dummy variables N Hon Mieu and E Hon Tre were significant (P = 0.01 and P = 0.002, respectively), as was the time factor (year 2002, P = 0.01), implicating that there were significant changes in the two years, 2002 and 2005. Effects of the depth factor were statistically significant (P = 0.002) in the explanation the variation of most of species composition, except for species belonging to two major families Fungiidae and Poritidae. With regard to depth effects, both sites of E Hon Tre remained itself, the deep site of SW Hon Mun seemed to represent a great increase. On the contrary, the shallow of N Hon Mieu was suffered the decline in abundance of species assemblage.
In attempt to further investigate the relationship among the three variables Depth, Area and Year, the 16 (2 × 4 × 2) combinations of variables, the so-called supplementary environmental variables, were superimposed onto the plane resulting from the main ordination (Figure 2). For the sake of clarity the symbols representing species variables in Figure 1 are not plotted again from Figure 2, but the two figures can be super-imposed and the effects of the explanatory variables (the vectors) remain the same. From the figure it becomes clearer that the differences in hard living coral assemblages between shallow and deep stations in the same area are as important as the differences among areas and between years.
From the previous reports (Tuan et al., 2005), eight human activities within the Nha Trang bay are commonly identified as probable agents of change in diversity. These are diving, other tourism activities (snorkelling, swimming, sport activities), aquaculture (lobster culture), commercial fishing, urban proximity, tourism expansion, shipping and navigation, as well as agricultural runoff from the Be river and the Cai river. The present study focused solely on the development and status of the aquaculture, fishery and tourism industries in recent years. Overall, the MPA community was negatively impacted by human activities in the period 2002 to 2005; i.e. after the creation of the protected area. (Table 2).
The prevalence of fishing and fishing-related aquaculture activities are probably main obstacles to the restoration of MPA’s biodiversity in the study period. Major influences of fishing to the MPA were derived from the increase in the number of fishing boats from 380 boats in 2002 to 527 boats in 2005, overfishing and poaching in a core zone in recent time. Meanwhile, a rapid development in the number of culture cages from 1,675 in 2001 to 5,096 in 2004, a high demand on wild seeds and using of ‘trash fish’ as preferred foods for culture, were considered as the main impacts of mariculture to the MPA. The “Temporary Regulation and Zoning Scheme” (2002) suggests a detailed zoning of fishing areas and regimes. However, this zonation is not respected in practice. Thus, allowing the free fishing, except for trawl and destructive fishing, in buffer zones and transition zones of Nha Trang Bay MPA will eventually create large negative influences that will prevent the recovery of coral assemblages. On the other hand, according to Mr. Nguyen Van Long (Institute of Oceanography, Nha Trang, Vietnam, pers. com.) the reason for the slow rate of restoration within the MPA is because it began with a low biodiversity level when it was established. However, there is a lack of obvious evidence from the present study to substantiate his suggestions; in fact, for many ecological groups and areas, density and diversity actually declined strongly from 2002 to 2005.
Initial funding for establishing the MPA in 2002 came mostly from the DANIDA (Denmark). At the end of 2005 external funding by donation was terminated. One of the biggest challenges for existence of the MPA is maintaining the sustainability of finance (Vinh et al., 2003). The present funding for running of the MPAs derives mostly from ‘conservation fees’ or ‘visitors fee’ applied to tourists. While tourism can be highly beneficial to the economy of the province and to the MPA in particular, it may also have negative indirect feedbacks to the MPA in the form of increasing pressure for fishing or aquaculture, or other disturbing human activities. Quantification of this linkage, could not be achieved in the present study, but must be a priority for future managerial studies. Further, high priority should also be given in the Nha Trang MPA to perform studies that quantify the sustainability of a high tourism-load vis-à-vis ecological achievement in the coral reef ecosystems.
Main objectives of this study focused on hard coral; though several of the human activities that affected marine protected areas were also discussed in this report. The recovering ability of MPA’s bio-diversity depends strongly on the pressure level from human activities. In addition, all human utilizations inside and outside the Nha Trang Bay MPA, including tourism, fishing, marine culture and shipping were planned and managed in an unsustainable way. Consequently, the management efficiency of Nha Trang Bay MPA was quite low.
Future plans expect a Vietnam National MPA network to be established by 2015, with 15 MPAs to be included. Presently only 2 MPAs are established at the national level (Nha Trang Bay MPA, Cu Lao Cham MPA) as well as two MPAs at the local level (Phu Quoc MPA, Con Co MPA). Although all MPAs were zoned and planned, human activities within and outside the MPAs mainly included tourism, fishing, marine culture and other economic development activities, which have been operating in undesirable ways. These activities have been causing negative affects to the MPAs. Future studies include: how to manage MPAs more efficiently, and how to quantify the linkage among tourism, fishing, marine culture and other human activities for better future management.
In order to answer these questions, support for research on approaches, and methodologies in order to manage MPA in an integrated and more efficient way will be necessary.