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

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 (Hopkins and Torres, 1989; e.g. Gaskett et al., 2001; 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.