DNA metabarcoding as a marine conservation and management tool: a circumpolar examination of fishery discards in the diet of threatened albatrosses

International audienceAlmost all of the world’s fisheries overlap spatially and temporally with foraging seabirds,with impacts that range from food supplementation (through scavenging behind vessels),to resource competition and incidental mortality. The nature and extent of interactionsbetween seabirds and fisheries vary, as does the level and efficacy of management andmitigation. Seabird dietary studies provide information on prey diversity and often identifyspecies that are also caught in fisheries, providing evidence of linkages which can be usedto improve ecosystem based management of fisheries. However, species identificationof fish can be difficult with conventional dietary techniques. The black-browed albatross(Thalassarche melanophris) has a circumpolar distribution and has suffered majorpopulation declines due primarily to incidental mortality in fisheries. We use DNAmetabarcoding of black-browed albatross scats to investigate their fish prey duringthe breeding season at six sites across their range, over two seasons. We identify thespatial and temporal diversity of fish in their diets and overlaps with fisheries operatingin adjacent waters. Across all sites, 51 fish species from 33 families were identified,with 23 species contributing >10% of the proportion of samples or sequences at anysite. There was extensive geographic variation but little inter-annual variability in fishspecies consumed. Several fish species that are not easily accessible to albatross, butare commercially harvested or by-caught, were detected in the albatross diet during thebreeding season. This was particularly evident at the Falkland Islands and Iles Kerguelenwhere higher fishery catch amounts (or discard amounts where known) correspondedto higher occurrence of these species in diet samples. This study indicates ongoing interactions with fisheries through consumption of fishery discards, increasing the riskof seabird mortality. Breeding success was higher at sites where fisheries discards weredetected in the diet, highlighting the need to minimize discarding to reduce impacts onthe ecosystem. DNA metabarcoding provides a valuable non-invasive tool for assessingthe fish prey of seabirds across broad geographic ranges. This provides an avenue forfishery resource managers to assess compliance of fisheries with discard policies andthe level of interaction with scavenging seabirds