Trophic ecology of three dominant myctophid species in the northern California Current region

Abstract

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...

Isotopic niches and trophic levels of myctophid fishes and their predators in the Southern Ocean

“…Segregation is likely to operate through a combination of different factors, including morphological, physiological, and behavioral adaptations. Trophic ecology of myctophids was recently related to two ecomorphological types, the so-called active and inactive species, with the former being diel vertical migrants that store lipids as triacylglycerols and the latter being nonmigratory and partly migratory species containing wax esters (see details in Suntsov and Brodeur 2008). Such a classification is not supported by myctophids from Kerguelen since most species are active migrants (Duhamel et al , 2005, which, depending on species, store either triacylglycerols or wax esters (Phleger et al 1999;Lea et al 2002b).…”

Larval stage duration, age and growth of blue lanternfish Tarletonbeania crenularis (Jordan and Gilbert, 1880) derived from otolith microstructure

“…Near Oregon, T. crenularis prey mainly on euphausiids, amphipods, and salps, and the largest specimens also consume bathylagid fish (Collard 1970;Hart 1973;Tyler and Pearcy 1975;Brodeur and Yamamura 2005;Suntsov and Brodeur 2008). In turn, T. crenularis constitutes an important prey item for many predators in the North Pacific, including jumbo squid (Field et al 2007;Zeidberg and Robison 2007), salmon, Sockeye salmon, albacore, Pacific hake, and sablefish (Rogachev et al 2000;Hart 1973, Davies et al 1988Buckley et al 1999;Nomura and Davis 2005), and Dall's porpoises (Ohizumi et al 2003).…”

Euphausiids in the diet of a North Pacific seabird: annual and seasonal variation and the role of ocean climate

“…Mar Ecol Prog Ser 390: [277][278][279][280][281][282][283][284][285][286][287][288][289] 2009 Tanasichuk 2002, Brinton & Townsend 2003, Croll et al 2005, Suntsov & Brodeur 2008. Research has shown that the population biology of both of these euphausiids is influenced by ocean climate (Tanasichuk 1998a,b, Marinovic et al 2002, Brinton & Townsend 2003, Dorman et al 2005), but in a complex manner that remains poorly understood (Abraham & Sydeman 2004).…”

“…Across the California Current System (CCS), for example, the euphausiids Euphausia pacifica and Thysanoessa spinifera are important prey for many vertebrate predators (Brodeur & Pearcy 1992, Ainley et al 1996, Tanasichuk 2002, Brinton & Townsend 2003, Croll et al 2005, Suntsov & Brodeur 2008. Research has shown that the population biology of both of these euphausiids is influenced by ocean climate (Tanasichuk 1998a,b, Marinovic et al 2002, Brinton & Townsend 2003, Dorman et al 2005), but in a complex manner that remains poorly understood (Abraham & Sydeman 2004).…”