Experimental studies on the feeding and reproduction of Calanoides patagoniensis (Copepoda, Calanoid) in a southern upwelling ecosystem of the Humboldt Current

Seasonal cohorts of the large-sized copepod Calanoides patagoniensis allowed testing the relative ability of this species to exploit food resources that prevail during winter time in southern upwelling ecosystems of the Humboldt Current. This was achieved by considering a local winter flagellate assemblage (WFA), Thalassiosira rotula isolated from the local spring phytoplankton and a laboratory culture of Prorocentrum minimum, as food offers in consecutive 96 h experiments. Ingestion rates (IR) varied between 7 and 14 μg C f−1 d−1, egg production reached a peak of 70 eggs while egg production rates (EPR) varied between 27 ± 6 and 31 ± 4 eggs f−1 d−1. Feeding and reproductive traits were dependent on food offer, and after 72 h both IR and EPR decreased by 28% and 40% respectively, when copepods were steadily fed with the diatom. The relatively high reproductive performance supported by WFA was notable; showing the feeding behavior of this species can couple with food availability in the field with successful reproductive outcomes. Migration strategies allowing remain in upper food-rich coastal waters along with this flexible trophic behavior may better explain why this species is among the most recurrent ones in these variable yet productive upwelling areas.

► Reproduction and feeding of Calanoides patagoniensis were first time estimated in the southern Humboldt Current.
► The relative ability of this species to exploit winter food conditions was tested.
► Food offer and feeding time were source of variability.
► Both variability factors affected copepod responses and winter food conditions supported adequately copepod fitness.
► This versatile trophic behavior helps to better explain copepod prevalence.