Vertical distribution of epiplanktonic Chaetognaths in the upper 100 m of the Hilutangan Channel, Cebu, The Philippines

A study was made on the vertical distribution of Chaetognatha in the Hilutangan Channel, based on analyses of 48 plankton samples. 30-min horizontal plankton tows were performed at depths of 1, 20, 50, 70 and 100 m in Jan 1972. 13 spp of 3 genera of maturing and mature chaetognaths were identified and counted. Sagitta inflata was the most common and abundant sp (63.0%), followed by S.neglecta (9.7%), S.robusta (8.6%), Sregularis (5.4%), S.serratodentata (4.2%), Krohnitta pacifica (2.9%), S.bedoti (2.3%) and S.decipiens (2.0%).S.pulchra (0.7%), S.ferox (0.5%), K.subtilis (0.3%), Pterosagitta draco (0.2%) and S.hexaptera (0.2%) were represented by < 1% each. Of these 13 spp in the upper 100 m, 12 were epiplanktonic while 1 sp, S.decipiens, is generally considered to be mesoplanktonic. 3 spp were classified as neritic, 3 as neritic-oceanic, and 6 as oceanic, indicating the dominant influence and strong influx of oceanic water into the Hilutangan Channel. Temp, salinity and DO content did not seem to influence the vertical distribution. Examination of gut contents showed that copedpods, followed by arrow worms, were most common in the chaetognaths studied.