Tue 16 Apr 2013: 3.00pm – William Eckman on “Ecology and Restocking of Giant Clams”

Qualifying  Examination

“Ecology and Restocking of Giant Clams”

William Eckman
Graduate Student,
Dept. Biological Sciences, NUS

Tue 16 April 2013: 3.00pm
@ DBS Meeting Room
(S3 Level 5,General Office #05-010)

Supervisor: Asst Prof Peter Alan, Todd

All are welcome


“As giant clams inhabit shallow waters, primarily in developing nations, many of their species are in danger of becoming directly extirpated by human activity, or of being unable to reproduce due to falling population densities. Over their long lifespans, giant clams produce large numbers of offspring, which have low survival rates at the larval and juvenile level. This is a successful reproductive strategy in the absence of human intervention.

Archaeologists know that humans have been harvesting clams for thousands of years, but modern technologies such as commercial fishing boats and SCUBA gear are depriving clams of refugia from which to repopulate other reefs. Increasing water turbidity due to coastal development, eutrophication, and dredging can make deeper water uninhabitable to giant clams, forcing their populations to reestablish in areas where they are more vulnerable to harvesting, tropical storms, and increasing water temperatures.

There is a significant amount of scientific literature regarding giant clams, particularly regarding their anatomy, physiology, and their symbiotic relationship with zooxanthellae. However, there are major gaps in the areas of their general ecology, reproductive behavior, and larval stages.

I will present the results of my experiments to determine giant clam larval tolerances to elevated water temperature, reduced light penetration, and reduced salinity.

I will also outline a proposed general ecology paper which will highlight and attempt to quantify the role that giant clams play in maintaining healthy reef ecosystems. There have been attempts in many countries to restock reefs with giant clams, although success rates have been low. Those efforts have not documented their strategy for placing clams in order to achieve high rates of survival and reproductive success.

I have carried out some preliminary investigations into giant clam reproductive behavior, and will continue and expand that work into a model resulting in guidelines for optimal clam placement. Clams in restocking efforts are initially placed in anti-predator cages, but their design is haphazard. I will experimentally compare several designs, including intertidal, benthic, and floating models, to determine which is most suitable for clam protection and growth in Singapore’s waters.

Finally, I plan to investigate the impacts of sediments on giant clams, using machinery which is capable of varying the timing and intensity of sediments to simulate various environmental or anthropogenic events.”


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