Preventing ecosystems from feeling clammy: what monitoring giant clam populations can tell us about human perseverance

By Maria Geoly, SRC Intern

Every aspect of our lives depends on the health of our natural resources. Clean water, nutrient rich soil, and access to timber are often considered humanity’s three most essential natural resources because they provide the four essential needs of living things: oxygen, water, food, and shelter. Often overlooked, however, is the crucial role that animals play in maintaining healthy resources. A healthy ecosystem is comprised of many different components (Figure 1), that work in a checks and balances system to maintain harmony.

Populations and demographics of the species comprising an ecosystem can be considered in decision toward ecosystem and resource management. The human implications of these decisions, however, are not always considered in the same way. An example of this comes from the Tuamotu atolls of French Polynesia, presented in a study from Georget et al. (2019).

The Tuamotu atolls used to have some of the largest populations of giant clams (Tridacna maxima) on Earth (Figure 2). Over thirty years, researchers had monitored the number of giant clams in this area –the ocean floor was divided into many squares or “quadrants” and giant clam individuals were counted within random squares, to estimate the number of animals in that habitat.

From 2005-2012, hundreds of giant clams started dying off very quickly due to unusual weather patterns. The drastic change in population was observed by the atolls’ residents, however the method used by researchers to monitor population did not. This methodology, known as “LIT-Q” testing, is an accurate way to measure abundant species, but as a species’ numbers decline, “BT” sampling methods, which use one very long but thin quadrant at a time, tend to be more precise.

As scientists realized their mistakes, they decided to try both methods at once, in old and new giant clam habitats, to see if their past data was incorrect. Computer simulations were used to make models of both data sets, and scientists found that each testing method gave different estimates for each site, with “BT” sampling being the most accurate.

This study is important because it recognizes the need for flexibility and reflexivity in scientific practice. In Tuamotu and other remote fisheries across the globe, fishing quotas are determined by the estimated population densities of a species. If the numbers are off, unsustainable policy could be written that may lead to overfishing, harming entire ecosystems and the people who rely upon them. As in the case of Tuamoto, scientists actively questioned if what they were doing was right and used creative problem solving to fix past mistakes. The revaluation of what once worked helped the area recognize that overfishing of giant clams was occurring, and fishing quotas have since changed to support the sustained health both the giant clams and of the reef systems supporting them.

Persevering through the daunting task of fixing such a big data mistake is hard, but the reward that comes with new understanding and solutions to large problems like overfishing is well worth the struggle. Tuamoto serves as a global example of why scientific methodology should often be questioned and reevaluated. The long-term benefits are ecologically worth it.

Work cited 

Georget S, Van Wynsberge S, Andréfouët S (2019) Understanding consequences of adaptive monitoring protocols on data consistency: application to the monitoring of giant clam densities impacted by massive mortalities in Tuamotu atolls, French Polynesia. ICES J Mar Sci 76:1062–1071. doi: 10.1093/icesjms/fsy189