Tawi-Tawi, An Island Richer Than You Expected

 By: KD Dijan | Kataegis

    Tawi-Tawi, recognized for its rich diversity of coral reef fishes, demersal fishes, marine turtles, and macroalgae, has revealed 90 previously unrecorded fish species through environmental DNA (eDNA) analysis of seawater, highlighting the potential of molecular techniques in documenting marine biodiversity.

    More than the already recorded 266 species on the island, eDNA reveals that the city has a wider variety of fishes than those already listed.

    From the seawater of Tawi-Tawi, lies the traces left by the fishes like their mucus, skin cells, waste, and other biological materials. In the study published in Ocean and Coastal Management in 2026, samples of seawater were collected in three of the municipalities namely: Simunul, Sitangkai, and Panglima Sugala. Using these samples, it will undergo eDNA metabarcoding to analyze the traces left by the fishes to identify multiple species at once without the need to catch the fishes individually.

    By using eDNA, the study identified 134 species across 115 genera, and 52 families. When combined with records of the fishes that are being sold in the markets of Tawi tawi, there are a total of 493 species documented in the island. In all of these species, 90 of them were not listed in the existing datasets and were only identified through eDNA allowing a more comprehensive inventory of fish biodiversity.

    However, data from market surveys may have difficulty in documenting fishes that are not usually caught due to it being small in size and one advantage of eDNA is its ability to detect species that may be overlooked by market surveys. Among the species detected through eDNA but absent from the market data is the Rastrelliger faughni or island mackerel, which is classified as Vulnerable on the International Union for Conservation of Nature Red List and has a decreasing global population trend. Its detection highlights the potential of eDNA monitoring to identify species of conservation interest. Such findings suggest that eDNA can help researchers build a more complete picture of marine life, supporting future monitoring and fisheries management in Tawi-Tawi.

    Tawi-Tawi, beyond being home to a rich diversity of fish, also holds potential as a site for strengthened marine conservation and management. By establishing a more comprehensive baseline of its fish species, the study provides valuable information that can guide future conservation efforts.