We examine the feeding ecology of characteristic micronekton species inhabiting the mid-slope reg... more We examine the feeding ecology of characteristic micronekton species inhabiting the mid-slope region ($700 to 1,500 m depths) o southern Tasmania. Five ®shes, Diaphus danae, Hygophum hanseni, Lampanyctus australis (Myctophidae), Phosichthys argenteus (Phosichthyidae) and Chauliodus sloani (Chauliodontidae), were sampled by depth-strati®ed midwater trawling on a diel and seasonal basis. Overall, 74 prey taxa were identi®ed from 2,132 stomachs. Euphausiids (mostly Euphausia spinifera and E. similis) and calanoid copepods (mostly Pleuromamma species) were the main prey of the three myctophids; P. argenteus ate ®shes and decapods in addition to the euphausiids, while C. sloani ate only ®shes. Copepods were less important in the diets of larger D. danae, L. australis and P. argenteus and were replaced by euphausiids in the myctophids and by ®shes in P. argenteus. In autumn, when euphausiid biomass increased six-fold, all three myctophids and P. argenteus fed most intensively and consumed a high proportion of euphausiids. The three myctophids appeared to feed nocturnally. Dierences in the timing and duration of feeding corresponded to dierences in their spatio-temporal overlap with key prey. Daily rations of H. hanseni (1.93% dry-weight biomass) and L. australis (1.43%), estimated from data on stomach fullness, were typical for temperate myctophids and higher than that of the non-migratory P. argenteus (0.43%). The vertical ux of near-surface plankton production to the mesopelagic food web is based primarily on diel feeding in the upper water column (<500 m) rather than consumption of species that migrate seasonally into the deeper mesopelagic zone. Because species such as P. argenteus and C. sloani feed above the third trophic level, their pre-dators, including the commercially important orange roughy, are feeding between levels four and ®ve.
We examine the feeding ecology of characteristic micronekton species inhabiting the mid-slope reg... more We examine the feeding ecology of characteristic micronekton species inhabiting the mid-slope region ($700 to 1,500 m depths) o southern Tasmania. Five ®shes, Diaphus danae, Hygophum hanseni, Lampanyctus australis (Myctophidae), Phosichthys argenteus (Phosichthyidae) and Chauliodus sloani (Chauliodontidae), were sampled by depth-strati®ed midwater trawling on a diel and seasonal basis. Overall, 74 prey taxa were identi®ed from 2,132 stomachs. Euphausiids (mostly Euphausia spinifera and E. similis) and calanoid copepods (mostly Pleuromamma species) were the main prey of the three myctophids; P. argenteus ate ®shes and decapods in addition to the euphausiids, while C. sloani ate only ®shes. Copepods were less important in the diets of larger D. danae, L. australis and P. argenteus and were replaced by euphausiids in the myctophids and by ®shes in P. argenteus. In autumn, when euphausiid biomass increased six-fold, all three myctophids and P. argenteus fed most intensively and consumed a high proportion of euphausiids. The three myctophids appeared to feed nocturnally. Dierences in the timing and duration of feeding corresponded to dierences in their spatio-temporal overlap with key prey. Daily rations of H. hanseni (1.93% dry-weight biomass) and L. australis (1.43%), estimated from data on stomach fullness, were typical for temperate myctophids and higher than that of the non-migratory P. argenteus (0.43%). The vertical ux of near-surface plankton production to the mesopelagic food web is based primarily on diel feeding in the upper water column (<500 m) rather than consumption of species that migrate seasonally into the deeper mesopelagic zone. Because species such as P. argenteus and C. sloani feed above the third trophic level, their pre-dators, including the commercially important orange roughy, are feeding between levels four and ®ve.
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Papers by J. Koslow