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No-take marine protected areas have been widely recommended for both biodiversity protection and fishery management Agardy 1994; Roberts 1997 Lubchenco et al. 2003; Planes et al. 2009, and an increasing number of no-take areas are being planned and implemented (Airame et al. 2003; Fernandes et al. 2005; Green et al. (in press); Planes et al. 2009). Although the conservation benefits of marine reserves are clear, the debate about whether reserves can benefit fisheries worldwide remains a major roadblock (Lester et al. 2009). The debate suggests that larvae from highly productive populations in marine reserves may move outside reserves and enhance populations in fished areas (Stobutzki 2001; Hilborn et al. 2004; Palumbi 2004; Gaylord et al. 2005; Sale et al. 2005). A few studies have shown spatial and temporal patterns of recruitment or abundance that suggests larvae exported from reserves can enhance nearby fished populations (Pelc et al. 2009; Tawake et al. 2001; Tawake et al. 2002; Murawski et al. 2000; Cudney-Bueno et al. 2009; Hockey et al. 1994; Stoner et al. 1998; Stoner et al. 1996; Beukers-Stewart et al. 2004; Beukers-Stewart et al. 2005). However, the larvae spillover effect remains controversial (Ref), partly because empirical evidence remains limited (Ref).
To explain the relative scarcity of empirical evidence, inherent difficulties in collecting and interpreting the data need to document larvae export. Benefits from larvae export may be widespread but probably diffuse, and the signal of export may be too weak to detect relative to the high spatial and temporal variability of recruitment (Ref.). Due to this reason, the data are difficult to interpret unless studies employ a before-after-control-impact (BACI) design (Ref).
In addition, the debate about larvae export often centers on whether export occurs. Some studies have demonstrated that reserves often lead to dramatic increases in larval production and that larvae disperse on scales far larger than reserves sizes (Ref25-27, 1, 28), which suggest that some export of larvae in reserves is nearly certain. However, the more questions on how far larvae travel and how to tag larvae have discussed a lot recently. A number of studies have demonstrated some methods for measuring larval dispersal distances. Of which rely on identifying the location of an individual's parents by using highly polymorphic genetic markers (Planes et al. 2009). Several recent studies using microsatellite DNA markers for paternity analysis have been documented (Ref). Although parentage analysis has been used to determine levels of local replenishment, this approach estimating connectivity among subpopulations of marine fishes is not well documented. However, Planes et al. (2009) was the first large-scale to apply the DNA parentage analysis to examine larval connectivity among marine reserves in Kimbe Bay, New Britain, Papua New Guinea, focusing on one species of fish, orange clownfish (Amphiprion percula).
In this paper, it is planning to solve three major questions on: (1) examining whether the net export occurs in marine reserves, or in other words, whether marine reserves benefit fished areas; (2) examining a broad of fish larval connectivity among marine reserves; (3) examining how far the fish larvae go from marine reserves.
To examine the questions above, this study will be conducted in Namyit Island, one of the islands in Sparitly Island, in South China Sea, and the study will divide the trial into two sections, including section I, comparing the density and biomass of fish species between the fished and protected zones by using before-after-control-impact-pairs (BACIP) design at Namyit Island in the Sparitly Island, South China Sea; section II, using parentage analysis to examine a broad of fish larval connectivity among marine reserves in Sparitly Islands, and using "mark and recapture" approach to find out how far the fish larvae go.
The Namyit Island is located in the southern part of Spratly Islands in the South China Sea, with an area of 5.3 hectares. Although there is no document recording that Namyit Island is a marine protected area, we will conduct the experiment here and establish this island as marine protected area (MPA). A total of 12 sites were selected for monitoring around Namyit Island (six Fished Areas and six Control Areas). The length of each site is 100m along the coast. Each site extends from the shore to the 50m out of island (Fig. 1). There are three transects at each site, with 25m long along the length of the coast.
Figure 1 Fished areas and Controlled Areas in Namyit. A total of six Fished areas and six Controlled areas will be established there.
This survey will be conducted every year lasting over 20 years from September 2010. Therefore, at the first five years, those controlled areas are still allowed to fishing. But after five years, they will be set as controlled areas, which are unfished areas. All transects within each site will be sampled by using standard fishing gears. We will use microsatellite DNA marker for tagging fish (this approach will be used for trial of section II as well) and recapture fish across all transects within each site. The data will be collected on abundance and size structure of the fish community, such as body length, weight.
As the finding of Planes et al. (2009), the A. percula larvae dispersed to adjacent subpopulations up to 35km away. We believe that these data provided evidence that from a single reserve might contribute to the resilience of subpopulations at other reserves within a network of MPAs. However, the problem is that for other fish species are still less understood. This field study will focus on a broader of fish species than Planes et al. (2009). This study will be conducted in September 2010 and we will record the number of marked fish when we do the trial in section I. To examine larval connectivity among marine reserves, we will recapture the fish at the nearest two islands at Itu Aba Island and Sin Cowe Island, which are 22.10km and 52.10km to Namyit Island, respectively (Fig. 2). We will recapture the fish in 2011, which will target on those juvenile fish that are recruited between September 2010 and March 2011. Moreover, we will evaluate DNA parentage analysis by comparing the results with those from a previous study based on transgeneration isotope labeling (TRAIL) (Planes et al. 2009).
Figure 2 Location maps of three island, Namyit Island, Itu Aba Island, and Sin Cowe Island, in Spratly Island in South China Sea.
In addition, in this study, we predict that the some of the fish larvae will go further area than 50km. The number of fish that will go different distances from the Namyit Island reserve (distances <30km, 30km< distances < 50km, distances > 50km) will be counted in this study. The aim of this study is to understand the fish larvae behavior that where the fish go and how far they will go. Through the results to monitor the reserves management and plan where are good for establishing marine reserves. The data will be displayed by using computer-based program, such as GIS-based software.
Significance and results prediction
Based on the BACIP design, the previous study of Galzin et al. (2004) showed that the fish density was increasing between 1987 and 2006 whatever in fished areas and controlled areas (Fig. 3). So, in this study, we predict that we will get a similar result that the density of total fish community will increase after a long-term protection. The management of controlled areas will benefit those fished areas, which will increase the density of fish community as well. For examining the fish larvae connectivity, we assume that we will offer a new evidence for a broader of fish larvae connection among the marine reserves. Furthermore, we assume that the distance between 30km and 50km will find more fish larvae. However, the distance less than 30km and the distance more than 50km will find relatively less fish larvae.
Figure 3 Density of total fish on the outer slope at Tiahura between 1987 and 2006 (Galzin et al. 2004).
Our approaches, based on the spatial and temporal scales, provide a powerful tool for assessing local replenishment and connectivity in marine populations that may be applied to other marine reserves. The BACIP design, DNA parentage analysis, and "mark and recapture" approach offer new and largely opportunities to directly measure the density/biomass of fish and fish dispersal in marine ecosystems. This information is vital to the spatial and temporal management of marine species, particularly for evaluating the optimal size and spacing of reserves in MPA networks (21, 28, Planes et al. 2009).
Therefore, the aim of this study is trying to make a further understanding for the design of the reserves to maintain biodiversity and biomass of fish in local scale, and to offer the evidence for marine reserves benefiting local fishery.