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

Abstract

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.