Situated in the northeastern part of Oriental Mindoro, Lake Naujan is a significant freshwater body covering approximately 216 square kilometers, making it the fifth-largest lake in the Philippines. Beyond its size, the lake serves as a vital habitat for diverse aquatic species, a source of livelihood for local fishing communities, and a key area for national efforts focused on the conservation of inland water resources.

However, Lake Naujan faces a range of environmental challenges, including the spread of invasive species, the impacts of climate change, and increasing anthropogenic pressures. These issues highlight the need for timely and coordinated conservation interventions. Ongoing initiatives led by the DA-NFRDI aim to address these concerns and support the sustainable management of this Ramsar-listed wetland.

Living landscape of Lake Naujan

Designated as a national park in 1956 by Presidential Proclamation No. 262, signed by President Ramon Magsaysay, Lake Naujan is more than just a scenic gem. Fed by mountain streams and drained by the Butas River, which flows into the Tablas Strait, the lake forms an intricate ecological network vital to the communities of Naujan, Pola, Socorro, and Victoria.

Naujan Lake’s ecological significance goes beyond its size and beauty. It was declared a Wetland of International Importance under the Ramsar Convention on November 12, 1999, making it the second designated Ramsar Site in the Philippines, alongside Agusan Marsh Wildlife Sanctuary in Agusan del Sur and Tubbataha Reefs Natural Park in Palawan. This recognition emphasizes the lake’s global environmental significance, particularly in terms of biodiversity conservation and ecosystem services.

As part of the Naujan Lake National Park (NLNP), the lake is a critical habitat in the East Asian–Australasian Flyway, serving as a feeding and wintering area for 19 species of migratory birds, including tufted ducks (Aythya fuligula). It also supports large flocks of herons, egrets, rails, plovers, and bitterns, and is a known refuge of the endemic and threatened Philippine duck (Anas luzonica).

More than just a haven for wildlife, Naujan Lake is also a home to people. At least three Mangyan tribes – Alangan, Hanunoo, and Tadyawan – live within the NLNP boundaries, relying heavily on the lake for fishing and other means of livelihood. The cultural and economic ties of these Indigenous Peoples to the lake further emphasize its role not only as a natural sanctuary but also as a cradle of human heritage and survival.

Endemic wonder and encroaching intruders

At the heart of Lake Naujan’s natural heritage is the paitan (Barbodes hemictenus), a small but significant endemic fish species. This species belongs to the Cyprinidae family and is classified as vulnerable on the International Union for Conservation of Nature (IUCN) Red List.

Once dominant in the lake’s waters, paitan has seen a dramatic decline in its population over the years. In a report titled, “Fishes of Naujan Lake National Park, Oriental Mindoro, Philippines” by Bonifacio Labatos, Jr., the decline has been attributed to the introduction of non-native cyprinids, including common carp (Cyprinus carpio carpio) and goldfish (Carassius auratus), which were initially introduced for fishery enhancement. Today, paitan is mostly confined to a few tributaries of the lake, its former territory now encroached upon by more aggressive and adaptable invasive species.

The introduction of non-native fish species into Lake Naujan has become a pressing ecological concern. A recent study published by The Philippine Journal of Fisheries in 2024, 13 non-native freshwater fish species in the lake were evaluated using the Aquatic Species Invasiveness Screening Kit (AS-ISK). Notably, the research found that over 60 percent of these species pose a high risk of invasiveness under future climate conditions, with redbelly tilapia (Coptodon zillii), Nile tilapia (Oreochromis niloticus), and guppy (Poecilia reticulata) leading the list.

These invasive species compete with native and endemic fauna for food and habitat, threatening biodiversity and altering ecological balance. Their adaptability to varying salinity levels, pollution, and climate conditions makes them formidable ecological disruptors. For species like paitan, the continued dominance of non-native fish puts their survival at greater risk, underlining the urgency of protective measures and science-based interventions.

NFRDI’s initiatives in Lake Naujan

Recognizing these challenges, the NFRDI expanded its National Stock Assessment Program (NSAP) to include inland waters in 2023. Following successful pilot assessments in Lakes Taal and Buhi, NFRDI began research in Lake Naujan in 2025. The goal is to establish a robust dataset on fish populations, gear use, fishing effort, and reproductive cycles, information critical for policymaking and conservation.

From April to May 2025, a comprehensive inventory was conducted across 17 lakeside barangays in Naujan, Pola, Socorro, and Victoria. The results revealed that 1,302 fishers are actively operating around the lake, with the largest concentration in Barangay Bayani, Naujan (243).

Additionally, the study documented 1,079 fishing vessels, with nearly 66 percent motorized, reflecting a significant level of mechanization in local fishing operations. The gear inventory identified 12 types of fishing equipment, totaling 110,592 units. The prawn pot (bubo) emerged as the dominant gear, making up a staggering 92,327 units, which suggests that fish trap-based harvesting is the most widespread method in the lake.

These findings provide an essential baseline for understanding the ecological and socio-economic dynamics at play in Lake Naujan. Moreover, they underscore the necessity of implementing evidence-based fisheries management, particularly in the face of threats from invasive species, illegal practices, and climate change.

Lake Naujan is at a crossroads. Its ecological importance is matched only by the risks it now faces. But with dedicated science, empowered local communities, and collaborative governance, its waters can continue to nourish both people and nature for generations to come.

In safeguarding Naujan, the Philippines is also defending a national treasure. ### (Cyrenes Moncawe)