Metabarcoding of Broad‐Diet Nototheniid Fish Stomachs Reveals Newly Detected Antarctic Parasite Signals and Potential Host Associations

ABSTRACT Parasites shape marine food‐web structure by increasing network connectivity and adding trophic links and include important pathogens that can pose risks to ecosystem health. Despite their growing ecological and economic relevance, parasite diversity remains largely unexplored in Antarctic marine systems, particularly among protist lineages. Here, we present an 18S rDNA metabarcoding survey of parasite diversity in Antarctic fish, using stomach contents from two nototheniid species collected in Potter Cove (Isla 25 de Mayo/King George Island), contributing to the limited number of studies applying this approach in the region. We identified 242 parasitic OTUs, representing 16% of OTU richness and 9% of total reads, with metazoans dominating in terms of read abundance and protists contributing most to overall diversity. Multivariate analyses revealed high inter‐individual variability and limited effects of host species, fish length, or sex, whereas depth emerged as the main structuring factor for parasite assemblages, driven primarily by prey‐associated protists. This study provides a snapshot integrating potential fish parasites with putative prey‐associated and environmentally derived parasite taxa, revealing previously undocumented molecular records in Antarctic bentho‐pelagic communities and expanding current knowledge of Antarctic parasite diversity. In addition, sequence‐based correlation analysis inferred putative associations between newly detected parasite taxa and local hosts, generating hypotheses of potential food–web interactions. Notably, we detected multiple protistan taxa of known pathogenic relevance rarely or never reported in Antarctic marine systems. This finding underscores the potential of combining broad‐diet fish as natural samplers with metabarcoding to survey local parasite diversity and to support surveillance of emerging disease risks in Antarctic ecosystems undergoing rapid environmental change.