Podeswa Ya., Pakhomov E.A. 2015. Feeding ecology of pelagic decapods in the North Pacific Subtropical gyre: implications for active carbon transport // Arthropoda Selecta. Vol.24. No.3: 317–334 [in English].
Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 2020-2207 Main Mall, Vancouver, BC, V6T1Z4, Canada. E-mail: email@example.com
KEY WORDS: Pelagic shrimps, feeding, North Pacific subtropical gyre, Sergestidae, Caridea, backscattering layers, mesopelagic food webs.
ABSTRACT. Pelagic decapods were collected during October 6–12, 2004 off the southwest coast of Oahu Island, Hawaii. Samples were collected using various micronekton sampling gears in the shallow backscattering layer (SSL, 0–120 m) at night and deep backscattering layer (DSL, 500–700 m) during both day- and nighttime. Three different gears were used, allowing a wide range of macrozooplankton and micronekton to be sampled: a 3 m2 (mouth opening) Isaacs-Kidd Midwater Trawl with a 5 mm mesh size, a 4 m2 Hokkaido University Frame Trawl with a 3 mm mesh size, and a 140 m2 pelagic Cobb trawl with a mesh size narrowing to 10 mm at the cod end. A total of 30 decapod taxa were identified. Amongst the 22 species with sufficient representation, three migration groups were identified: full migrators (27% of all species), partial migrators (59%), and non-migrators (14%). It was found that decapod diet varied not only with size, but also with taxonomic affinity. Diets of nine migrating decapod species mainly included small pelagic crustaceans: calanoid copepods, euphausiids, decapods, ostracods and amphipods, as well as fish, radiolarians, chaetognaths and pelagic mollusks. Generally, there was no significant overlap (<30% of diet similarity) in the diet composition between various species. However, on three occasions the dietary overlap exceeded 50% (up to a max 71%) in three species pairs: Notostomus elegans and Oplophorus spinosus due fish consumption; Sergia gardineri and S. scintillans due to consumption of calanoid copepods, particularly Pleuromamma spp., and radiolarians; and finally Neosergestes orientalis and Stylopandalus richardi due to preying upon crustaceans in general with the large copepod contribution. All decapods fed more in the SSL at night than in the DSL during the day or night. However, feeding in the DSL was equal to 9.7–44.7% of feeding in the SSL by weight. A significant, on average ~20%, decapod feeding occurring at the daytime depth in tropical gyres needs to be taken into account in currently emerging biochemical models aiming to quantify active downward carbon flux via migrating large plankton. The question further arises whether such a pattern holds true for decapods in other regions of the world ocean and for other migratory species of macroplankton and micronekton community which urgently requires further studies.