MEPS 288:173-182 (2005)  -  doi:10.3354/meps288173

Feeding and egg production of Oithona similis in the North Atlantic

Claudia Castellani1,3,4,*, Xabier Irigoien2, Roger P. Harris3, Richard S. Lampitt1

1Southampton Oceanography Centre Waterfront Campus, European Way, Southampton SO14 3ZH, UK
2AZTI (Fisheries and Food Technological Institute), Herrera Kaia Portualdea, 20110 Pasaia, Spain
3Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK
4Present address: BODC (British Oceanographic Data Centre), Proudman Oceanographic Laboratory, 6 Brownlow Street, Liverpool L3 5DA, UK

ABSTRACT: Although cyclopoids of the genus Oithona are considered the most abundant copepods in the marine environment, there is still very little information about what sustains their population and almost constant reproduction rate throughout the year. Feeding and egg production rate (EPR) of O. similis were measured at coastal and oceanic stations during 3 cruises in the North Atlantic between April and November 2002. O. similis ingested ciliates preferentially to other components of the nano- and microplankton (herein nano-microplankton), which only became a more important component of the copepod diet when the abundance of the former decreased to low concentrations. EPR did not show significant seasonal differences, with 2.13 ± 0.67 eggs female–1 d–1 in spring, 1.61 ± 0.32 eggs female–1 d–1 in summer and 1.60 ± 0.15 eggs female–1 d–1 in winter. The ingestion rates measured at many oceanic stations and in winter were often too low to sustain EPR. Egg production efficiency (GGE) >100% indicated that sustained EPR might have relied, particularly in winter, on alternative food sources such as a more carnivorous diet and/or on the faecal pellets of euphausids.

KEY WORDS: Oithona similis · Cyclopoids · Feeding rate · Egg production rate · Microzoo-plankton · Gross growth efficiency

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