Seasonal Occurrence of Anguillid Elvers in Cagayan River, Luzon Island, the Philippines

Abstract

Some 5400 specimens of anguillid elvers and youngs collected in 1970–1974 from the Cagayan Estuary of Luzon Island, the Philippines, and the neighbouring eel ponds were studied, especially on species composition and their seasonal occurrence. The results obtained are as follows: 1) The elvers and youngs, based on sectional counts of vertebrae, were identified as Anguilla celebesensis, A. marmorata, A. japonica and A. bicolor pacifica. 2) Besides sectional counts of the vertebrae, the caudal cutaneous pigmentation was found to be useful for specific identification of the Philippine eels in the early elver stage, 3) The elvers occurred in the Estuary during most of the year, and were most abundant in March and August. 4) A. marmorata, one of the dominant elvers, was found mainly in the first half of the year, with a peak in March, while A. celebesensis, another dominant elver, was seen during most of the year, attaining its peak in August. 5) A. bicolor pacifica and A. japonica, the minor species in the present observation, appeared mainly in October to February, and January and February, respectively. © 1976, The Japanese Society of Fisheries Science. All rights reserved.