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What DNA in fish stomachs can tell us about the Southern Ocean


Clarke, LJ and Trebilco, R and Polanowski, AM and Deagle, BE, What DNA in fish stomachs can tell us about the Southern Ocean, Proceedings of the 2nd Kerguelen Plateau Marine Ecosystem and Fisheries Symposium, 13-15 November 2017, Hobart (In Press) [Refereed Conference Paper]

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Mesopelagic fish form an important link between zooplankton and higher trophic levels in Southern Ocean food webs, however their diets are poorly known. Most of the dietary information available comes from morphological analysis of stomach contents (e.g. Gaskett et al. 2001; Hopkins & Torres 1989; Pusch et al. 2004; Shreeve et al. 2009) and to a lesser extent fatty acid and stable isotopes. DNA sequencing could substantially improve our knowledge of mesopelagic fish diets, but has not previously been applied. We used high-throughput DNA sequencing (HTS) of the 18S ribosomal DNA and mitochondrial cytochrome oxidase I (COI) to characterise stomach contents of four myctophid and one bathylagid species collected at the southern extension of the Kerguelen Plateau (southern Kerguelen Axis), one of the most productive regions in the Indian sector of the Southern Ocean. Diets of the four myctophid species were dominated by amphipods, euphausiids and copepods, whereas radiolarians and siphonophores contributed a much greater proportion of HTS reads for Bathylagus sp. (Fig. 1a). Analysis of mitochondrial COI showed that all species preyed on Thysanoessa macrura, but Euphausia superba was only detected in the stomach contents of myctophids. Size-based shifts in diet were apparent, with larger individuals of both bathylagid and myctophid species more likely to consume euphausiids (Fig. 2), but we found little evidence for regional differences in diet composition for each species over the survey area. The presence of DNA from coelenterates and other gelatinous prey in the stomach contents of all five species (Fig. 1b and c), which are largely missed with morphological analysis, suggests the importance of these taxa in the diet of Southern Ocean mesopelagics has been underestimated to date. Our dual marker approach (18S and COI) combined the broad taxonomic coverage of 18S (e.g. to detect taxa such as radiolarians not amplified by COI) with the taxonomic resolution of COI (e.g. to distinguish different krill species). The COI marker also helped avoid misidentification of fish species. Indeed, the presence of four distinct COI operational taxonomic units assigned to Bathylagus sp. supports the presence of cryptic diversity in Southern Ocean specimens of this genus (Dettai et al. 2011).

Item Details

Item Type:Refereed Conference Paper
Keywords:mesopelagic zone, stomach content, food webs, energy transfer, metabarcoding, jellyfish
Research Division:Biological Sciences
Research Group:Genetics
Research Field:Population, Ecological and Evolutionary Genetics
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Biological Sciences
UTAS Author:Clarke, LJ (Dr Laurence Clarke)
UTAS Author:Trebilco, R (Dr Rowan Trebilco)
UTAS Author:Deagle, BE (Dr Bruce Deagle)
ID Code:128579
Year Published:In Press
Deposited By:Ecology and Biodiversity
Deposited On:2018-10-01
Last Modified:2019-06-11
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