2012. Review of Significant Trade - Cites

Tridacna spp.
Islands have been reported since 2006.
Management: The trade and export of wild-sourced specimens were reported to be banned
in the Solomon Islands (Solomon Islands Consolidated Legislation, 1996), however the trade
and export of farmed specimens is permitted (Solomon Islands, 2009). It was reported that
subsistence harvesting was not regulated (Green et al., 2006) although local, traditional
management practices were practiced in some areas (Kinch et al., 2006) whereby
overharvested areas are left to recover for some years to guarantee sustainable resource
(Hviding, 1993). Further details are provided in the genus overview.
In large-scale grow-out trials conducted at 11 village farms in the Solomon Islands, T. crocea
was found to grow to a mean size of 5.2 cm (±0.81 s.d.) in 22 months, and its survival rate
after 17 months was 39 per cent (±22.6 s.d.) (Hart et al., 1998). Due to these comparatively
low growth and survival rates, Hart et al. (1998) regarded the species less suitable for village
farming than T. derasa or T. maxima, in spite of its high demand in aquarium trade.
Tridacna derasa (Röding, 1798): Solomon Islands.
Biology: Tridacna derasa was reported to commonly reach a shell length of 50 cm, with a
maximum of 60 cm reported (Kinch and Teitelbaum, 2010). It reaches maturity as a male at
5 years and as a hermaphrodite at 10-11 years (Raymakers et al., 2003). It prefers the outer
edge areas of coral reefs and may occur from shallow water to up to 20 m depth (Kinch and
Teitelbaum, 2010).
Distribution in range State: The native range of T. derasa was reported to extend from
Australia to Philippines and from Indonesia to Tonga (Wells, 1996a).
The species was described as globally “frequent” (Dance, 1974) although with a “patchy”
geographic distribution, being less frequent in some areas (Adams et al., 1988). It was
considered to be the only Tridacna species with a limited distribution within the Solomon
Islands Main Group Archipelago (MGA) (Govan, 1988; Richards et al., 1994). The species had
been recorded in Marau Sound, Nggela and Russel Islands in the Central Province and in
north Marovo Lagoon in the Western Province, although it was considered possible that it
also occurred elsewhere (Wells, 1997). Ramohia et al. (2005a) recorded the species in the
Maravaghi community-based MPA in Nggela, however the species was not recorded in
similar surveys conducted in the Sisili and Taburu community-based MPAs in Nggela in the
Central Province (Ramohia et al., 2005b).
Population trends and status: Globally, population declines have been reported by
IUCN et al., (2006b), Wells (1997), Isamu (2008) and Othman et al. (2010). Local or national
extinctions were reported to have occurred in several countries (IUCN, 2006b). T. derasa was
categorised as Vulnerable in the IUCN Red List, although it was noted that the assessment
needed updating (Wells, 1996a).
T. derasa was considered to be “reasonably abundant” in the Solomon Islands (IUCN, 2006b).
Oengpepa (1993) reported severely depleted populations in many areas within the Solomon
Islands, referring to surveys conducted between 1987-1991 by the International Center for
Living Aquatic Resources Management (ICLARM). In a survey of key invertebrate species
conducted at 66 sites in the main island group, T. derasa was found to be the rarest of the
Tridacna species, occurring at 11 per cent of the studied sites at average densities of less than
4 individuals per hectare (Ramohia, 2006). These densities were considered low compared to
those recorded in earlier studies, which was regarded as a cause of concern (Ramohia, 2006).
Kinch et al. (2006) did not record the species in surveys conducted in the Marovo Lagoon in
the Western Province, concluding that this was possibly a result of overexploitation. In
transect surveys conducted in the Maravaghi community-based MPA in Nggela in Central
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