Proximate composition and energy density of nototheniid and myctophid fish in McMurdo Sound and the Ross Sea, Antarctica

Abstract

Nototheniid and myctophid Wsh are primary prey for marine piscivores, yet little is known about their nutritional value. In this study, we characterized the proximate composition [PC: water, fat (neutral lipids), crude protein (CP) and ash] and energy density (ED; kJ g ¡1 ) of Wfteen Wsh species from McMurdo Sound and the Ross Sea, Antarctica. We assayed the entire Wsh for all species except for the large Antarctic toothWsh, Dissostichus mawsoni (muscle tissue only). On a wet mass basis (WM), Wsh were variable in composition: moisture content ranged from 64.9 to 87.3% WM, fat from 0.5 to 17.4% WM, CP from 7.7 to 16.7% WM, ash from 11.2 to 21.0% FFDM (fat-free dry mass), and ED from 2.9 to 10.3 kJ g ¡1 . Myctophids and pelagic nototheniids such as Pleuragramma antarcticum and D. mawsoni were high in fat content (7-17% WM), while a bathylagid and benthic nototheniids including most Trematomus spp. and Lepidonotothen squamifrons were low in fat (0.5-4% WM). The epibenthic Trematomus species (T. eulepidotus and T. lepidorhinus) were intermediate. Energy density tracked fat content, with highest values in myctophids and pelagic nototheniids. The variation in nutrient and energy density conWrms that prey composition must be taken into account when modelling energy and nutrient Xuxes within the Antarctic ecosystem. Further analyses of prey collected over a number of diVerent locations and seasons are needed in order to determine how the nutritional value of certain species might aVect annual or decadal variation in reproductive success or population size of top predators.

Review: the energetic value of zooplankton and nekton species of the Southern Ocean

“…The energy density of adult Pleuragramma antarctica is closer to that of the myctophid fishes, and evidence suggest that the energy density of adults would be even higher in fully grown individuals (Van de Putte et al 2010). This suggestion is supported by a relatively high energetic density of larger fish from the Ross Sea (Lenky et al 2012). This increased energy density could be a result of increased lipid content, which increases with age and size.…”

“…The main focus lies on nototheniid, myctophid and bathylagid species. The lipid content of myctophids is in general high, while nototheniids are more variable in composition, which shows a difference between the two families that is possibly related to habitat use (Lenky et al 2012). This is reflected in their dry-weight energy density, which was generally high for myctophids, while for nototheniids it ranged from values similar to crustaceans to values similar to myctophid fish.…”

“…High energy densities of 29.9 and 29.4 kJ g −1 DW were reported for Dissostichus mawsoni (Antarctic toothfish) and Dissostichus eleginoides (Patagonian toothfish), respectively (Durand and Nicolle 1980; Lenky et al 2012). Dissostichus mawsoni occurs mainly in high Antarctic waters.…”

“…Of the species listed in Lenky et al (2012), Lepidonotothen squamifrons , Trematomus bernacchii , Trematomus hansoni , Trematomus pennelli and T. scotti are benthic species (Eastman and DeVries 1982; Lenky et al 2012). Therefore, they are suggested to have less lipids and a higher proportion of ash (Hagen et al 2000; Lenky et al 2012).…”

“…Of the species listed in Lenky et al (2012), Lepidonotothen squamifrons , Trematomus bernacchii , Trematomus hansoni , Trematomus pennelli and T. scotti are benthic species (Eastman and DeVries 1982; Lenky et al 2012). Therefore, they are suggested to have less lipids and a higher proportion of ash (Hagen et al 2000; Lenky et al 2012). Furthermore Trematomus spp., Notothenia coriiceps and Gobionotothen gibberifrons mainly feed on benthic organisms which can have a relatively low energetic value such as polychaetes, molluscs and amphipods (Kock 1992; Lenky et al 2012).…”