A total of 12 feeding experiments were conducted in the northern Gulf of Aqaba during spring (March/April) and autumn (September/October) 2002 at the Marine Science Station (MSS) in Aqaba. Females of three species of clausocalanids were selected: Clausocalanus farrani, C. furcatus and Ctenocalanus vanus. Natural occurring particle (NOP) larger than 5 μm were investigated as food source. The ambient chlorophyll a concentration at sampling depth (∼70 m) ranged between 0.15 and 1.00 μg chl a l-1 and NOP concentrations ranged between 1.78 and 14.0 × 103 cells l-1 during the sampling periods. The division of particles into five size classes (5-10, 10-20, 20-50, 50-100 and >100 μm) revealed that most of the particles were found in the size classes below 50 μm (81-98%), while most of the natural occurring carbon (NOC) was concentrated in the size classes larger than 20 μm (70-95%). Ingestion rates were food density dependent rather than size dependent ranging between 0.02 and 1.65 × 103 NOP ind-1 day-1 and 0.01 and 0.41 μg NOC ind -1 day-1, respectively, equivalent to a body carbon (BC) uptake between 0.4 and 51.8% BC day-1. The share of the size classes to the total ingestion resembled in most cases the size class composition of the natural particle community. © 2006 Springer-Verlag.