ZooMS as a tool for understanding prehistoric pelagic fishing: Insights from archaeological shark and scombrid remains on Fais Island, Micronesia, over the last two millennia

The capture of fast-moving marine predators, such as sharks and scombrids, played a crucial role in human subsistence and cultural evolution, with advanced fishing techniques emerging alongside the maritime expansions of Neolithic populations across the Pacific. However, challenges in identifying their remains in the archaeological record have constrained our understanding of their significance. Fais, a raised coral island in Micronesia, has been inhabited for 1800 years, with archaeological evidence revealing a reliance on fishing strategies targeting inshore taxa but also pelagic taxa including some species of sharks and scombrids. Using ZooMS, this study analysed archaeological bones, mostly vertebrae, from the Powa (FSPO) archaeological site, Fais, with 100 % and 93 % success rates of retrieving collagen fingerprints in scombrids (n = 77) and sharks (n = 54) respectively. The scombrids were overwhelmingly dominated (97 %; n = 75) by skipjack tuna (Katsuwonus pelamis), with the remaining specimens deriving from two distinct species, yellowfin tuna (Thunnus albacares) and wahoo (Acanthocybium solandri). In contrast, the shark remains were more taxonomically diverse and evenly balanced, with at least five distinct taxa across much fewer samples. Although lacking a complete enough reference database to make confident assignments to species, we could infer that at least more than one half of the identifications were to groups that closely match the silky shark (Carcharhinus falciformis; n = 20), and the Galapagos shark (C. galapagensis; n = 11); these two sharks have well-known associations with tuna and their identifications are consistent with some of the dominant species inferred through morphology. A third relatively abundant type (n = 17) yielded spectra that could not be matched to our reference material, though plausibly of the only other relatively abundant tuna-associated taxon, the silvertip shark (C. albimarginatus). A further two species were represented by one sample each, one of which was a good match for the whitetip reef shark (Triaenodon obesus), but the other also not close to any of the reference material included in this study. Nonetheless, the categorization of the shark remains in this study using ZooMS disagrees with the categorization by morphology reported elsewhere, where multiple ‘types’ are found in previously identified morphological types and vice versa. From a methodological viewpoint, this study clearly demonstrates the substantial difference in confidence that can be assigned to a taxonomic identification that well-curated ZooMS databases can offer, particularly when supported by genomic sequence information. By improving the taxonomic resolution of archaeological fish identifications these findings enhance our understanding of ancient fishing practices while suggesting a need for expanded research to address gaps in species-level identification and ecological data.