Abundance, Distribution and Species Composition of Cyclopoid Copepods Along a Transect Traversing the Upwelling Zone off Northern Zamboanga Peninsula, Philippines

The abundance, distribution and species composition of cyclopoids were studied in the largest sardine fishing ground in the Philippines during a coastal upwelling event in March 2014. Zooplankton samples were collected in six stations along a transect extending from the coast to about 50 km offshore in Dipolog Bay, Northern Zamboanga Peninsula, Mindanao. A 100 μm NORPAC net was hauled vertically to sample successive depth strata (0–65 m, 65–135 m, 135–200 m). Out of 28 zooplankton groups, cyclopoids made up 12.2 % of mean total zooplankton density. Forty-two cyclopoid species (overall mean density: 503.6 ind.m -3 ) were identified, with Oncaea clevei Früchtl, 1923 (25.4 %) as the most abundant, followed by Oncaea scottodicarloi Heron and Bradford-Grieve, 1995 (13.6 %), Triconia conifera (Giesbrecht, 1891) (9.2 %), Oncaea media Giesbrecht, 1891 (7.2 %) and Corycaeus dahli Tanaka, 1957 (7.0 %). The higher abundance (732.9 ind.m -3 ) of cyclopoids at 0–65 m than at 135–200 m (220.2 ind.m -3 ) was attributed to the high abundance of phytoplankton in the upper euphotic zone. Cyclopoid density was highest in station 4 (938.3 ind.m -3 ) at the margin of the upwelling zone. This is attributed to the time lag between phytoplankton and zooplankton build-up and the dispersive effects of wind-driven drift.