Assessment of migratory fishes in Butas River, Naujan, Oriental Mindoro, Philippines

Abstract

To determine the declining production of migratory fishes (milkfish, mullet, snapper, jacks) in Naujan Lake, environmental assessment of Butas River is being conducted. Water quality is being monitored and fish samples were collected once a month from April to December 2003. Four stations were considered: Station 1 with Barangay Melgar A; Station 2, Barangay Concepcion; Station 3, Barangay Dao; and Station 4, Barangay Bayani. Water temperature, pH, transparency, dissolved oxygen, and water depth were determined in-situ. Gill net or pante was used in collecting fish samples. Results show that water parameters are not significantly different between stations except water depth. Stations 2 and 3 (mid portion of the river) are relatively low compared to Stations 1 and 4. Migratory fishes collected are mullet, milkfish, and caranx in Stations 1 and 4. Water depth in the mid portion of Butas River is decreasing as a result of heavy sediment disposition. Siltation could be attributed to erosion and other activities like farming and construction of road along Butas River. Migratory fishes in Naujan Lake are considered endangered due to overfishing, introduction of exotic species, and construction of fish corral. Dredging Butas River is recommended to descend migratory fishes from Naujan Lake to Mindoro/ Tablas Strait and ascend from sea to lake. Dredging the river will increase its productivity as it has been noted that no ecological disturbance would occur during dredging. There is also a need to strictly implement Fisheries Administrative Order 217 Series of 2001 Obstruction to Defined Migratory Paths by the Local Government to protect migratory fishes in Naujan Lake.