TDA-IME Project Final Report June, 2013 component of mangrove ecosystem integrity - nursery habitat provision for commercially important aquatic species - can also be restored by replanting mangroves in degraded areas. Diverse communities of zooplankton, high abundance (reaching 105 individuals/m3) and biomass (up to 623 mg/m3) have been recorded in mangrove ecosystems (Robertson and Blaber, 1992), where they are believed to make an important contribution to coastal food webs. Zooplankton can be divided into three size classes: micro-zooplankton (organisms from 20 to 199 μm), meso-zooplankton (200 μm to 2 mm) and macro-zooplankton (larger than 2 mm). The micro-zooplankton includes foraminiferans, ciliates, rotifers, copepod nauplii, barnacle nauplii and mollusc veligers. Copepods are the most abundant group in the meso-zooplankton and jellyfish the most important macro-zooplankton. Mero-zooplankton (planktonic larval stages of benthic invertebrates) span the full range of zooplankton sizes and can constitute up to 70% of the zooplankton community (Kathiresan and Bingham, 2001). Chong and Sasekumar (1981) reported that post-larvae of the white prawn, Penaeus merguiensis, in mangrove nursery sites feed mainly on copepods, while juveniles consume mainly detritus, but also ingest foraminiferans, copepods, and crab and molluscan larvae. Other studies have also suggested that mangrove crab larvae may be an important food source in coastal aquatic food webs (Macintosh et al., 1991). They are easily identifiable from the unique shape of the zoea larvae stages, and therefore they could serve as a potential indicator of mangrove ecosystem health (= an aquatic productivity indicator). Mangrove - Fisheries Linkages A key transboundary research priority is to better understand the relationship between mangroves and coastal to offshore fisheries, from both an ecological and economic perspective. There is overwhelming evidence for the role mangroves play in supporting onsite and near-shore fisheries, as evidenced by the traditional knowledge of artisanal fishers in Asia who understand the role mangroves play as nursery grounds for many commercial aquatic species. Their local knowledge is well supported by findings from scientific studies on the life cycles of mangrove-associated species, ranging from fin-fish like mullets, snappers and mudskippers, to white shrimps and mud crabs (Macintosh, 1983; Ong and Sasekumar, 1984; Robertson, 1986; Vance et al., 1990; Moser et al., 2002; Bucholts et al., 2009). Fish larval studies along the Andaman Sea coast of Thailand have shown that larvae of the families Carangidae, Gobiidae, Clupeidae, Scianidae, Engraulidae Callionymidae Monocanthidae are abundant in mangrove ecosystems (reviewed by Macintosh et al., 1991). Conversely, in the Gulf of Thailand, destruction of mangrove forests was identified as a major cause of a decline in the number of fish species reported by Monkolprasit (1983). Boonruang and Janekarn (1985) recorded post-larvae of five species of commercially important penaeid shrimp in mangrove channels and along the seaward mangrove fringe in Phuket. At a transboundary scale, there appears to be a positive relationship between the area of mangroves and offshore fisheries yields (MacNae, 1974; Turner, 1977 and Martosubroto and Naamin, 1977), but it is very difficult to demonstrate a causal link to explain these earlier reported correlations (Gilbert and Janssen, 1998). The mangroves fringing enclosed shallow-water coastal areas, which include estuaries, bays, lagoons and larger formations like the inner Gulf of Thailand, provide habitat and food support to numerous commercially important fishery species including pelagic fish species (Clupeiidae, Latidae, Mugilidae, Lutjanidae), marine catfishes (Ariidae, Plotosidae), shrimp (Penaeidae, Sergestidae), crabs (Portunidae) and bivalve molluscs, chiefly oysters and cockles (UNEP, 2004). Scientific evidence suggests that the relationship is highly site specific, with factors such as tidal range and salinity being highly influential, in addition to the type of mangrove habitat per se (Vance et al., 1990; Ronnback et al., 1999). For this reason, 42
Transboundary Diagnostic Analysis of Indochina Mangrove Ecosystems
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