Current Fish Fauna of Mandulog River, Iligan City, Philippines

Abstract

This paper provides the current fish species richness, composition, distribution, and conservation status in the** Mandulog River,* Iligan City, Philippines, highlighting its ecological significance and the impact of anthropogenic activities. A total of Fourteen species from 13 families were recorded, consisting of- 12 native and two introduced species from three sampling sites (upstream, midstream, and downstream). Native species dominated the fish assemblage, with Fibramia thermalis (44.22%) and Planiliza subviridis (18.03%) being the most abundant. This study confirmed the first record of Barbodes tumba, a threatened endemic species confined to upstream areas, reflecting their vulnerability to habitat disturbance. Conservation assessments of the 12 native revealed that ten species (85.7%) are classified as “Least Concern”, one as “Endangered” and another one species as “Data Deficient”. This study also documented two invasive alien species, Oreochromis niloticus and Clarias batrachus. *The recent findings underscore significant threats to the Mandulog River’s biodiversity, including pollution, quarry mining, sedimentation, and invasive alien species. Recommendations emphasize conservation strategies targeting habitat restoration, invasive alien species management, and community-driven biodiversity monitoring to sustain the river’s ecological health and align with global conservation goals.

Introduction

Freshwater ecosystems, such as rivers, play a vital role in maintaining **biodiversity** and providing ecosystem services to human and natural systems. They are essential habitats for various aquatic species, including fish that contribute to the ecological balance, support livelihoods, and serve as indicators of environmental health (Jamandre, 2023). Among these, rivers in the Philippines, including the Mandulog River in Iligan City, stand out due to their rich ichthyofauna, comprising native and endemic species. However, these ecosystems face mounting challenges from human-induced disturbances such as overfishing, pollution, and invasive alien species environmental degradation (Guerrero, 2023).

The Mandulog River traverses urban and rural areas and supports diverse freshwater fish species. This river system, previously studied by Sempio et al. (2013), Vedra et al. (2013), and Tampus et al. (2015), has been a focal point for understanding the impacts of human activities such as quarrying, urbanization, unregulated fishing activities and landscape alterations on freshwater biodiversity. Quarrying activities, sedimentation, and pollution from surrounding communities significantly threaten aquatic habitats, as Buot et al. (2014) and (Vedra and Ocampo, 2016) highlighted. These threats have led to declines in native and endemic fish populations, echoing trends observed in similar freshwater systems across the Philippines (Gonzalez et al., 2023; Macalisang et al., 2023; Guerrero, 2023).

Past research efforts across Philippine rivers emphasieze the need to understand fish species composition and abundance, particularly as many species remain threatened or poorly documented (IUCN, 2019). Thus, this study aims to build on existing knowledge by providing the current of fish species composition, abundance, distribution, and conservation status in the Mandulog River. This work addresses critical gaps in understanding the river’s current ecological state, focusing on its biodiversity’s sustainability. The study align with global conservation priorities under the United Nations Sustainable Development Goals (SDGs), particularly SDG 6.6, which emphasizes the protection and restoration of water-related ecosystems, SDG 15.1, which focuses on the conservation, restoration and sustainable use of freshwater ecosystems and their services, SDG 15.5, which seeks to protect habitats, halt biodiversity loss and safeguard species from extinction, and SDG 15.8 which aims for prevention, reduction, control, and eradication of invasive alien species (UN SDG 2024).

Source : Current fish fauna in Mandulog River, Iligan City, Lanao Del Norte, Philippines