Lake Buhi, located in the Bicol region between the slopes of Mt. Iriga and Mt. Malimas, is recognized as the sole natural habitat of sinarapan (Mistichthys luzonensis), the world’s smallest commercially harvested fish.

Despite its minute size, which is barely larger than a grain of rice, sinarapan has held ecological, cultural, and economic significance for generations, serving as a source of livelihood and local identity. However, the population of sinarapan has experienced a marked decline in recent years.

A fish on the brink

Sinarapan was first documented in the early 1900s, once thriving in the clear, cool waters of Lake Buhi. Its unique size and endemic status even landed it in the Guinness World Records in 2001. Locals recall how easily it could be scooped from the lake using fine nets, its tiny silvery bodies glinting in the sun. It was not just a curiosity; it was a food source, a livelihood, and a symbol of natural heritage.

Today, that story is very different. By 2021, sinarapan was listed as “vulnerable” by the International Union for Conservation of Nature (IUCN). Over the decades, overfishing, habitat degradation, and the introduction of aggressive non-native species like tilapia and ayungin drastically reduced its population. Interventions that began in the 1970s, though well-meaning, also disrupted the delicate balance of Lake Buhi’s ecosystem. Recent fisheries assessments indicate the possible absence of sinarapan in Lake Buhi.

NFRDI steps in

In response to concerns regarding the possible disappearance of sinarapan, the local government unit (LGU) of Buhi formally requested the assistance of DA-NFRDI in 2023. The request aimed to assess and confirm the presence of sinarapan, not only in Lake Buhi, but also in nearby water bodies within the Buhi Wildlife Sanctuary (BWS), a designated protected area.

To address this, DA-NFRDI, through its Freshwater Fisheries Research and Development Center (FFRDC) in Taal, Batangas, expanded its stock assessment efforts to include Lake Buhi and its adjacent lakes. This initiative formed part of a broader objective to develop data-driven strategies for the conservation of sinarapan and the sustainable management of the lake’s fisheries resources.

The project, implemented from 2023 to 2024, aimed to evaluate the current condition of the lake’s fisheries, scientifically determine the status of sinarapan, and provide evidence-based recommendations for recovery and conservation. Key components of the study included fishing gear inventory, catch composition analysis, reproductive biology assessment, larval distribution surveys, and both morphological and genetic identification of fish species.

Where is sinarapan now?

The assessment findings raised significant concerns. According to the resource assessment conducted by DA-NFRDI, tilapia, a non-native but economically important species, has become the dominant fish in Lake Buhi. Other introduced species, such as ayungin and common carp, also comprise a substantial portion of the lake’s fish biomass. Although some fishers have reported the continued presence of sinarapan, further analysis revealed that the specimens were larval stages of ayungin and other small, transparent gobies that closely resemble sinarapan but are not the same species.

To verify these observations, DA-NFRDI conducted both morphological and genetic analyses on suspected sinarapan samples collected from Lake Buhi and adjacent water bodies. The results confirmed that the true sinarapan was absent from Lake Buhi. Misidentification was frequent, but no verified specimens of the species were found.

Despite this, findings from nearby Lake Manapao, a remote mountain lakelet within the Buhi Wildlife Sanctuary (BWS), offered encouraging results. Verified sinarapan populations were confirmed to be present and thriving in this location. In contrast, samples collected from Lakes Bato, Danao, Katugday, and Makuao did not yield any true sinarapan, reinforcing Lake Manapao’s importance as a critical habitat and potential last refuge for the species in the region.

To support conservation planning, DA-NFRDI also studied the reproductive biology of sinarapan in Lake Manapao. The species was found to likely exhibit protogynous hermaphroditism, beginning life as female and transitioning to male. The peak spawning season was identified in May, based on the presence of gravid females and patterns in gonadal development. These findings are crucial in guiding future protection efforts, especially during reproductive periods.

More than just one study

The stock assessment extended beyond sinarapan and revealed broader challenges affecting Lake Buhi’s fisheries.

A fisher and fishing gear inventory identified over 500 individuals actively engaged in fishing across the lake. The most commonly used fishing gears include gill nets (pukot), shrimp pots (bubo pambuyod), hand dredges (silo), and spearguns (sumbiling), among others. The majority of these are passive gear types, which generally exert lower pressure on fish stocks and habitats. Notably, the man push net, locally referred to as sarap, remains in use and is the only gear known to specifically target sinarapan. Overall, the gear types reflect a predominantly small-scale fishery, which, if appropriately managed, holds potential for long-term sustainability.

he assessment also evaluated the status of aquaculture operations within the lake. Findings indicated poor regulatory compliance, with a number of fish cages being unregistered, oversized, or installed in unauthorized areas. Productivity levels were low, and several environmental concerns were noted, including elevated ammonia concentrations, low dissolved oxygen levels, and organic pollution caused by uneaten feed. These issues suggest that, without adequate monitoring and regulation, aquaculture activities may negatively impact the lake’s ecological health.

Additionally, ichthyoplankton surveys, sampling fish eggs and larvae, provided insight into potential breeding grounds across the lake. Areas surrounding the old and newly established sanctuary zones exhibited the highest larval abundance, indicating their potential role as key nursery habitats. With proper protection and management, these areas could support the recovery and sustainability of fish populations in Lake Buhi.

Call to action

Effective conservation requires a sustained commitment across all levels of governance, from national agencies to local lakeshore communities. Scientific studies have identified the remaining habitats where sinarapan persists, documented its reproductive behavior, and outlined the primary threats to its survival. Moving forward, coordinated efforts are essential to protect these critical habitats, implement sustainable fisheries practices, and, if conditions allow, consider the eventual reintroduction of sinarapan into Lake Buhi.

Though the sinarapan is the smallest commercially harvested fish in the world, its conservation represents a significant challenge with broader implications. It highlights the importance of safeguarding even the most diminutive species as part of the country’s freshwater biodiversity. Through the integration of science, sound policy, and community engagement, Lake Buhi has the potential to once again support viable sinarapan populations and serve as a model for effective aquatic resource management. ### (Rita dela Cruz and Ma. Lourdes Merilles)