Cagayan River is the Philippine’s mightiest watercourse—the longest at about 400 kilometers and widest river in the country. Three major tributaries—Ilagan River, Magat River, and Chico River meet other streams and flow to the Cagayan River. The famous “lurung” fish abound in the river during the rainy season when the river is murky and the fishes swim upstream from the delta at Aparri to spawn. It empties at the Aparri estuary.