The feeding ecology of 3 dominant sympatric myctophid species (Tarletonbeania crenularis, Diaphus theta, and Stenobrachius leucopsarus) in the northern California Current System was investigated based on samples collected in June, August, and September of 2006. All 3 species fed predominantly on Euphausia pacifica, the most abundant euphausiid off the central Oregon coast. In contrast, the same 3 lanternfishes showed marked variation in utilization of other principal food categories, and stronger resource partitioning was evident in smaller individuals. The proportion of euphausiids in the diet of T. crenularis and S. leucopsarus gradually increased with increasing size. D. theta at intermediate sizes (31 to 60 mm) preyed heavily upon salps and hyperiid amphipods, whereas the largest specimens consumed mostly euphausiids. S. leucopsarus showed little changes in composition of principal food categories between months, while T. crenularis and D. theta consumed more hyperiid amphipods in June, euphausiids in August, and salps in September. No feeding on salps was recorded in S. leucopsarus for the entire study period. All 3 species showed variation in feeding intensity, stomach fullness, state of digestion, and number of prey species and prey items per stomach. A divergence in feeding strategies of these co-occurring lanternfishes appears to reflect their structural morphology and generally conforms to an ecological subdivision of this midwater family into 'active' and 'inactive' species. Active myctophids (T. crenularis and D. theta) consumed significantly larger amounts of protein-rich prey such as euphausiids, hyperiid amphipods, and salps, while inactive S. leucopsarus showed higher preference for slower-moving, lipid-rich Neocalanus copepods.
KEY WORDS:Myctophidae · Mesopelagic · Tarletonbeania crenularis · Diaphus theta · Stenobrachius leucopsarus · Feeding ecology · Ecomorphology · California Current
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 373: [81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96] 2008 Yamamura 2005). Myctophids represent an important trophic link between phytophagous zooplankton such as copepods and euphausiids and higher trophic level organisms such as salmon, tuna, seabirds, and marine mammals (see review in Brodeur & Yamamura 2005). They dominate the fish biomass in oceanic waters of the Northeast Pacific (Pearcy 1977, Gjøsaeter & Kawaguchi 1980, Beamish et al. 1999, and their transport onto continental shelves represents an important flux of energy into these systems, as represented in food web models of the California Current (Field et al. 2006).Three lanternfish species (Tarletonbeania crenularis, Stenobrachius leucopsarus, and Diaphus theta) form the bulk of micronekton fishes found in the NCC. These 3 species were reported to account for twothirds of all fishes collected in Isaac-Kidd midwater trawl tows in the upper 200 m off Oregon, USA (Pearcy 1964(Pearcy , 1977. Due to their high biomass and widespre...
