Feeding habits of three dominant myctophid fishes, Diaphus theta, Stenobrachius leucopsarus and S. nannochir, in the subarctic and transitional waters of the western North Pacific

Abstract

The feeding habits of 3 dominant myctophid fishes, Diaphus theta (vertical migrant), Stenobrachius leucopsarus (semi-migrant), and S. nannochir (non-migrant), were studied in relation to their diel vertical migration patterns using time-series sampling during the summers of 1994 to 1996 in the subarctic and transitional waters of the western North Pacific. D. theta and S. leucopsarus fed mainly on euphausiids (mainly Euphausia pacifica), copepods (mainly Metridia pacifica and the Neocalanus plumchrus/flemingeri group), and amphipods (mainly the Themisto japonica /pacifica group). The prey of S. nannochir was mainly copepods, but the species were different from those preyed on by D. theta and S. leucopsarus. D. theta fed on euphausiids, with 1 feeding peak during the daytime and another at night, but fed on amphipods only at night and on copepods throughout the entire diel cycle. The vertical migratory component of S. leucopsarus showed a significant diel feeding periodicity, feeding on euphausiids, copepods, and amphipods from dusk to midnight, while the non-migratory component did not feed actively at nighttime, and had a high frequency of empty stomachs. The non-migratory S. nannochir showed no diel feeding periodicity. The average ratio of stomach content weight/body weight was 2.2% during the day and 2.0% at night in D. theta, 0.8% during the daytime and 1.1% at night in the migratory S. leucopsarus, 0.6% at night in the nonmigratory S. leucopsarus, and 0.07 to 0.13% (avg. 0.11%) in S. nannochir. KEY WORDS: Myctophid fish · Diet composition · Diel feeding periodicity · Daily ration · Diel vertical migrationResale or republication not permitted without written consent of the publisher

Does location really matter? An inter-colony comparison of seabirds breeding at varying distances from productive oceanographic features in the Bering Sea

“…Although oceanic domains are thought to be relatively low in productivity (Springer and McRoy, 1993;Springer et al, 1996), deep-water prey are usually high quality, and may be very concentrated near the surface at night due to diel vertical migration even if total productivity of the water column is relatively low. Vertically migrating fish, squid, and zooplankton species that live in deep basin waters tend to store large energy reserves so they can fast for extended periods and maintain near neutral buoyancy over a wide range of depths and pressures (Moku et al, 2000;Visser and Jonasdottir, 1999). The diet of seabirds that forage over deep water basins usually include species with relatively high energy densities, such as northern lampfish (Stenobrachius leucopsarus), and northern smoothtongue (Leuroglossus schmidti; Iverson et al, 2007;Lance and Roby, 2000).…”

“…Diel vertical migrations of oceanic prey species can result in large temporal patchiness of food availability, with prey brought close to the surface during the night (Moku et al, 2000). Prey are distributed over a large range of spatial scales (Maravelias et al, 1996), with aggregations often described by a nested hierarchical patch structure (Fauchald and Erikstad, 2002;Kotliar and Wiens, 1990;Russell et al, 1992).…”

Diel and habitat-dependent resource utilisation of deep-sea fishes at the Great Meteor seamount (subtropical NE Atlantic): niche overlap and support for the sound-scattering layer-interception hypothesis

“…The nocturnal predation on myctophids at GMR is in accordance with their migration. Migrating myctophids are nocturnally present in depths of 150 to 500 m, where they prey on euphausiids, amphipods and copepods and are themselves subject to predation (Clarke 1978, Watanabe et al 1999, Moku et al 2000, Butler et al 2001. Thus, the daytime descent takes them below the reach of bentho-pelagic fishes at the top of shallow topography like GMR.…”

Production, metabolism and trophic importance of four pelagic amphipods in the Oyashio region, western subarctic Pacific

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