2012. Review of Significant Trade - Cites

Tridacna spp.
Indo-Pacific (including South China Sea and Coral Sea) to Indonesia, Marshall Islands and
the Great Barrier Reef in Australia (IUCN et al., 1996).
T. gigas was considered to be widespread in the Solomon Islands (Govan, 1988; Wells, 1997),
found in most parts of the country (Hviding, 1993). However, in transect surveys conducted
in 2004 in the Maravaghi community-based MPA in Ngella in Central Province (Ramohia et
al., 2005a), in the Sisili and Taburu community-based MPAs in Ngella in the Central
Province (Ramohia et al., 2005b), and in the Marapa and Simeruka MPAs in Marau Sound,
Central Province (Ramohia, 2004), the species was not recorded. Similarly, Kinch et al. (2006)
did not record the species in the Marovo Lagoon in the Western Province.
Population trends and status: The species was categorised as Vulnerable in the IUCN Red
List (Wells, 1996b), although the status assessment needs updating. Many populations in
Southeast Asia were considered to be in sharp decline (Othman et al., 2010).
Wells (1997) considered the Solomon Islands as the only country besides Australia to have
abundant populations of T. gigas, even if the species was considered to be found in low
numbers. Skewes (1990) stated that the populations of T. gigas in the Solomon Islands
showed no signs of local extinctions due to overfishing. Hviding (1993) reported that the
species was found “in reasonable numbers in most parts of Solomon islands”, but noted that
the populations were depleted in some areas. Oengpepa (1993) reported severely depleted
populations in many areas, referring to surveys conducted between 1987-1991 by the
International Center for Living Aquatic Resources Management (ICLARM) staff, and noted
that the decline was “continuing at an alarming rate”, and that it was “attributed to
overharvesting by coastal dwellers”.
In a survey of key invertebrate species conducted at 66 sites in the main island group of the
Solomon Islands, excluding the remote islands and atolls, Ramohia (2006) recorded the
species at 14 per cent of the studied sites; a total of 12 individuals were recorded in the
surveys and the average densities of 4 individuals or less per hectare were regarded as a
cause of concern (Ramohia, 2006). In related Rapid Ecological Assessment (REA) surveys,
T. gigas was recorded at 5 out of 113 sites, with each site surveyed covering an area
approximately 5000 m 2 (Turak, 2006).
Threats: Overexploitation for commercial and subsistence purposes was considered to be
the main threat to the species (IUCN et al., 1996; Wells, 1997; Othman et al., 2010). In the
Solomon Islands, Tridacna spp. were reported to be frequently used for subsistence purposes
(Horokou et al., 2010), and often used as ceremonial food and food for feasts (Hviding, 1993).
Lukan and Brough (2011a) noted that due to its attractive colouring and easy care, the
species was particularly suitable for aquarium trade.
Kinch et al. (2006) suggested that overexploitation was possibly the cause of the species’
absence in surveys conducted in the Marovo Lagoon in the Western Province.
Mass mortalities were reported in the Solomon Islands in 1992 in both, farmed and natural
populations (Newman and Gomez, 2000), possibly linked with a pronounced El Niño event
(Richards et al., 1994). Studies also showed that human-induced increase in water turbidity
(Elfwing et al., 2003), bleaching (Leggat et al., 2003), decreased salinity levels and copper
pollution (Blidberg, 2004) were associated with reduced growth of T. gigas.
Trade: As the Solomon Islands has not yet submitted a CITES annual report, trade figures
are based on data submitted by importers. According to data in the CITES Trade Database,
direct trade in T. gigas from the Solomon Islands reported by importers 2000-2010 consisted
of 1777 shells, of which 99 per cent were wild-sourced, and 971 live specimens, of which
95 per cent were captive-born or captive-bred (Table 3). The majority of shells were
175