Ecological survey of the endangered Dawkinsia arulius (Arulius Barb) and Barbodes montanoi (Paitan Barb) in the Banawang River Continuum, Philippines
Jericho A. Trio
Abstract
The ecological integrity of the Banawang River Continuum in Negros Island, Philippines is increasingly challenged by invasive species and habitat alteration. This study characterized the hydrological profile and ichthyofaunal assemblages of the said lotic system to understand species co-occurrence mechanisms within this environment. Using remote sensing and ecological surveys across a 14.8 km stretch, the research analyzed watershed delineation and fish diversity utilizing Pearson’s Chi-square tests and community metrics. Hydrological results indicated a drainage network heavily skewed toward short, first-order tributaries (78.95%), denoting a uniform stem rather than a complex dendritic network. Biological findings revealed a heterogeneous ecosystem where invasive species disrupt natural River Continuum Concept predictions. The upstream sector was dominated by the introduced Danio rerio (50%), while the midstream exhibited a biodiversity bottleneck characterized by Poecilia reticulata abundance and low species richness. Conversely, the downstream segment demonstrated the highest ecological evenness (J’ = 0.945). A critical finding is the vertical stratification of the endangered native Barbodes montanoi, which maintains a mesopelagic niche (5–6 m). This depth preference effectively segregates the native species from surface-oriented invasive (Dawkinsia arulius) and deep-demersal natives (Barbodes binotatus). These results imply that while the river is physically uniform, it is ecologically fragmented, with bathymetric partitioning serving as a vital survival mechanism for endemic fauna amidst invasive pressures.
Keywords
Philippine barbs, cyprinids, endangered fishes, limnology, river continuum concept, river remote sensing
Author information & Contribution
School of Environmental Science and Management - University of the Philippines Los Baños (UPLB). Email: jatrio@up.edu.ph
Disclosure statement
No potential conflict of interest was reported by the author.
Funding
This work was not supported by any funding.
Institutional Review Board Statement
Not Applicable
AI Declaration
The author declares the use of Artificial Intelligence (AI) in writing this paper. In particular, the author used Gemini and Grammarly in sourcing reviews of related literature and refining clarity of sentence structure. The author takes full responsibility in ensuring proper review and editing of contents generated using AI.
Notes
Acknowledgement
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Cite this article:
Trio, J.A. (2026). Ecological survey of the endangered Dawkinsia arulius (Arulius Barb) and Barbodes montanoi (Paitan Barb) in the Banawang River Continuum, Philippines. International Journal of Science, Technology, Engineering and Mathematics, 6(1), 67-88. https://doi.org/10.53378/ijstem.353330
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