AB 26:229-244 (2017)  -  DOI: https://doi.org/10.3354/ab00690

Diel changes of food sources and their contributions to nutrition of Orientomysis mitsukurii in a sandy shore environment

Kazutaka Takahashi1,*, Akira Kuwata2, Takeo Suzuki3, Tatsuki Toda3, Keiichiro Ide2

1Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
2Tohoku National Fisheries Research Institute, 3-27-5 Shinhama-cho, Shiogama, 985-0001, Japan
3Faculty of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
*Corresponding author:

ABSTRACT: Diel changes in feeding habits and the relative contributions of daytime and nighttime diets to the nutrition of the mysid Orientomysis mitsukurii in a sandy shore environment were determined by field sampling and additional laboratory experiments. O. mitsukurii was distributed just above the bottom during the daytime but a subpopulation swam up into the water column at night. Nighttime swimming activity was prevalent in small individuals but progressively decreased at larger body sizes, while the gut pigment contents of all mysid size classes consistently increased at night. Stomach content analysis revealed that O. mitsukurii individuals of all size groups ingested sedimented particulate organic matter (POM) containing large quantities of clay minerals during the daytime, whereas they mainly foraged on planktonic diatoms in the water column at night. Estimated in situ algal ingestion rates at night accounted for approximately 80-95% of the daily carbon assimilation. O. mitsukurii also exhibited high efficiency in grazing on planktonic diatoms in laboratory experiments. Conversely, daytime sedimented POM carbon accounted for only a minor proportion (5-20%) of the daily carbon assimilation. The utilisation patterns of the different food sources were confirmed by carbon and nitrogen stable isotopic signatures in the benthic community. Our results suggest that efficient utilisation of primary producers, such as planktonic diatoms, by O. mitsukurii is beneficial for maintaining the species’ high abundance from an ecological transfer efficiency perspective, and that sedimented POM is an alternative food source for securing the basic energy required for their survival, particularly when phytoplankton availability is low.

KEY WORDS: Mysidae · Omnivore · Nighttime feeding · Vertical migration · Sandy shore environment · Detritus · Diatoms

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Cite this article as: Takahashi K, Kuwata A, Suzuki T, Toda T, Ide K (2017) Diel changes of food sources and their contributions to nutrition of Orientomysis mitsukurii in a sandy shore environment. Aquat Biol 26:229-244. https://doi.org/10.3354/ab00690

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