Journal of the Marine Biological Association of the United Kingdom

Table of Contents - May 2012 - Volume 92, Issue 03  

Research Article

Food habits of threadfin hakeling Laemonema longipes along the Pacific coast of northern Japan

O. Yamamuraa1 c1 and T. Nobetsua2

a1 Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Kushiro, 085-0802 Japan

a2 Shiretoko Nature Foundation, Rausu, 086-1822 Japan

Abstract

Food habits of threadfin hakeling Laemonema longipes, the dominant demersal fish in the upper continental slope of the western sub-Arctic North Pacific, were described based upon >1400 specimens collected off north-eastern Honshu Island and south-eastern Hokkaido Island, Japan. Threadfin hakeling depended exclusively on pelagic organisms including copepods Neocalanus cristatus, Euphausia pacifica, shrimps Sergestes similis, firefly squid Watasenia scintillans and myctophids Diaphus theta. Threadfin hakeling showed a clear size-dependent dietary variation, with mesozooplankton and shrimps being important for small- and medium-sized fish (≤400 mm standard length (SL)), and myctophids being important for large-sized fish (>400 mm SL). Since all of these prey undertake diurnal vertical migration, it was concluded that threadfin hakeling take an important role in capturing energy and materials transported from the epipelagic zone to the bathypelagic layer over the upper continental slope. Dietary variation among different areas, seasons and depths were also examined. Of these, areal difference was rather obscure reflecting common prey field in the Tohoku and Doto areas under the prevalence of the North Pacific Intermediate Water, whereas clear seasonal difference was found in the Doto area; the 0-group of walleye pollock Theragra chalcogramma was ingested only in the late summer and early autumn in this area.

(Received August 23 2010)

(Accepted January 31 2011)

(Online publication July 13 2011)

Keywords

Correspondence:

c1 Correspondence should be addressed to: O. Yamamura, Ecosystem Studies, Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Kushiro, 085-0802 Japan email: orioy@affrc.go.jp