INFLUENCE OF WATER QUALITY AND HABITAT CHARACTERISTICS ON FISH ASSEMBLAGES IN TWO RIVER SYSTEMS OF NORTHERN MINDANAO, PHILIPPINES

Sonnie Vedra; Hannah Marielle Sindayen; John Ulysses Sindayen; Ramon Francisco Padilla; Magdalena Dulay; Michael James Baclayon

doi:10.31413/nat.v14i1.20298

Authors

Sonnie Vedra sonnie.vedra@msunaawan.edu.ph
College of Environment and Life Sciences, Mindanao State University, Naawan, Misamis Oriental, Philippines. https://orcid.org/0009-0004-2151-0488
Hannah Marielle Sindayen hannahmarielle.sindayen@msunaawan.edu.ph
College of Environment and Life Sciences, Mindanao State University, Naawan, Misamis Oriental, Philippines. https://orcid.org/0009-0005-8237-4675
John Ulysses Sindayen johnulysses.sindayen@msunaawan.edu.ph
College of Environment and Life Sciences, Mindanao State University, Naawan, Misamis Oriental, Philippines. https://orcid.org/0009-0003-6766-5429
Ramon Francisco Padilla ramonfrancisco.padilla@msunaawan.edu.ph
College of Environment and Life Sciences, Mindanao State University, Naawan, Misamis Oriental, Philippines. https://orcid.org/0000-0002-3096-4578
Magdalena Dulay magdalena.dulay@msunaawan.edu.ph
College of Environment and Life Sciences, Mindanao State University, Naawan, Misamis Oriental, Philippines. https://orcid.org/0009-0006-7953-1155
Michael James Baclayon michaeljames.baclayon@msunaawan.edu.ph
College of Environment and Life Sciences, Mindanao State University, Naawan, Misamis Oriental, Philippines. https://orcid.org/0009-0002-1342-3582

DOI:

https://doi.org/10.31413/nat.v14i1.20298

Keywords:

Fish assemblages, Freshwater ecology , Multivariate analysis, River systems, Water quality

Abstract

This study assessed fish assemblages and their relationships with environmental variables in the Initao and Gimangpang Rivers of northern Mindanao, Philippines, to inform evidence-based river management. A total of 409 individuals representing five families and at least nine native species were documented, with Gobiidae and Eleotridae dominating both systems. The Initao River recorded slightly higher abundance (n = 213) than the Gimangpang River (n = 196). Mean fish relative density differed significantly among riverine reaches (F = 11.12; p < 0.02), increasing from upstream to downstream, although assemblage structure between rivers was not significantly different (F = 1.22; p > 0.05). Species dominance varied, with Channa macrocephalus prevalent in Initao (21.60%) and Sicyopterus lagocephalus in Gimangpang (23.98%). Water quality parameters (DO, BOD, nitrate, phosphate, temperature, pH) were within recommended limits for aquatic life, indicating generally suitable habitat conditions. PCA (49.16% explained variance) identified substrate type, riparian vegetation, depth, landscape cover, and water quality as key drivers of assemblage patterns. Practically, these findings highlight the importance of protecting riparian vegetation, regulating land use, and maintaining water quality to sustain native fish populations. Fish collection was conducted under appropriate local authorization and followed environmental ethics protocols, including minimal handling stress, selective sampling, and immediate release of non-retained specimens to reduce ecological disturbance.

Keywords: fish community; freshwater ecology; multivariate analysis; freshwater systems; tropical water quality.

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