Author : Vedra, Sonnie Abragan

Summary : The biology and ecology of indigenous freshwater gobies might be affected by water pollution resulting from human activities, which posed changes in the water quality of the river. Hence, a study was conducted in the upstream, midstream and downstream parts of Mandulog river system, Iligan City, Northern Mindanao in quarterly basis for one year to determine the species composition, abundance, morpho-meristic characteristics, sexual dimorphism, body proportionality, GSI estimates, water quality, climatic conditions, and human-related activities. Total number of individuals of all goby species was 1590, with 895 (56.28%) and 695 (47.72%) gobies collected during dry and wet seasons, respectively. There were 141 (15.75%), 559 (62.45%) and 195 (21.78) individuals of all goby species recorded in the upstream, midstream, downstream parts of the river during dry season, while 147 (21.15%), 372 (53.52%), and 176 (25.32%) were recorded during wet season. Ten goby species were found in three families namely, Belobrancus belobranchus (4.78%), Giuris margaritacea (10.25%), Oxyeleotris lineolata (31.76%), Awaous melanocephalus (13.46%), A. ocellaris (12.14%), Glossogobius celebius (8.99%), G. giuris (8.68%), Periophthalmus barbarus (3.52%), Sicyopterus lagocephalus (5.28%), and Rhyacichthys aspro (1.13%). Generally, the morphometric and meritic attributes did not differ significantly for each goby species. Only four out of ten species exhibited sexual dimorphism, namely: G. celebius, P. barbarus, O. lineolata and G. margaritacea. Body proportioned body structure. A decreasing trend of gonadosomatic index was observed from species found in the upsteam towards downsteam, that in turn, may indicate a slight sensitivity to water pollution. R. aspro, which can only be in the upstream and midstream, may be the only species that is sensitive to water pollution, although the quality of Mandulog River is still within the DENR standards that could support the goby population. This study revealed that the current domestic (i.e. toilet use, kitchen wastes, laundry and bathing), agricultural (application of pesticides and fertilizers), quarry and small-scale mining activities done within the river and its periphery did not pose any serious threats to goby population in terms of the level of pollution generated. However, it is imperative that the river must be protected from overexploitation and pollution impacts for the economic and ecological benefits, particularly on providing sustainable fishery resources for the present and future generations. The increasing level of awareness based on the knowledge, perception and attitude of the residents towads the riverine and terrestrial resources might probably empower themselves and the mobilzed through a concerted and holistic effort on biodiversity conservation and sustainable development programs of the LGU ang other institutions.