Fluted giant clam (Tridacna squamosa) restocking experiment in an urban turbid reef environment

Abstract

Abstract Giant clam populations in Singapore are endangered due to historical exploitation, habitat loss, and sediment pollution. Transplanting cultured giant clams onto reefs is a potential conservation strategy. This study examined the growth and survival of three initial size classes (50.0–60.0 mm, 60.1–70.0 mm, >70 mm) of cultured juvenile fluted giant clams, Tridacna squamosa, transplanted to three reef sites under two caging treatments (caged and uncaged). After 145 days, there was no significant difference in clam survival within the size classes and within caging treatments across reef sites, even though environmental conditions varied greatly between sites. However, there was a significant effect of initial size class on T. squamosa survival, with higher survival with increasing size class (50.0–60.0 mm: 11.1%; 60.1–70.0 mm: 34.1%; >70.0 mm: 46.9%). Clams in caged treatments had significantly lower survival (16.7%) than uncaged clams (43.1%), likely due to biofouling atop caged treatments reducing light availability. Growth rates in the caged treatment (2.2 ± SD 1.8 mm month−1) were also lower than those in the uncaged treatment (3.9 ± SD 2.2 mm month−1). By optimizing transplant procedures for Singapore's turbid reef conditions, T. squamosa restocking efforts could play an important role in boosting local population numbers to facilitate natural recovery.