MEPS 271:261-266 (2004)  -  doi:10.3354/meps271261

Importance of ciliates as prey of the euphausiid Euphausia pacifica in the NW North Pacific

Yoshizumi Nakagawa1,3,*, Takashi Ota1, Yoshinari Endo1, Kenji Taki2, Hiroya Sugisaki2

1Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
2Tohoku National Fisheries Research Institute, Shiogama 985-0001, Japan
3Present address: Fisheries Laboratory of Kinki University, 1-5, Shirahama, Nishimuro, Wakayama 649-2200, Japan

ABSTRACT: We investigated the feeding of Euphausia pacifica on ciliates, especially naked ciliates, in laboratory and field experiments in which cultured Strombidium conicum, or natural food assemblages, or both were given, and estimated the importance of ciliates as prey. E. pacifica ingested cultured S. conicum at rates of 0.04 to 0.07 µgC krill-1 h-1 at low ciliate concentration and 1.01 to 3.24 µgC krill-1 h-1 at high ciliate concentration, when S. conicum was given as the sole prey. The daily ration on naked ciliates ranged from 0.02 to 1.8% of body carbon when natural food assemblages enriched with S. conicum were given, and from 0.05 to 2.3% of body carbon when S. conicum was given as the sole prey. Our results provide indirect evidence that E. pacifica ingests naked ciliates and plays a role in linking microbial food webs to the classical grazing food chains.

KEY WORDS: Euphausia pacifica · Feeding · Naked ciliates · Strombidium conicum · Food removal

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