Despite the frequent occurrence of fish fossils in the field, related studies are noticeably rare in Taiwan. The scant fossil record of fish in the literature sharply contrasts the high diversity of modern fish in this region. This is often due to the scarcity of well-preserved materials, limited exposure that covers long geological ages, and lack of comprehensive sampling design. Over the years, unstudied new fish fossils have been collected and accumulated. Several old and published specimens stored in private collections are lost. In this study, we evaluated potential horizons yielding fish fossils, examined the current status of published specimens with updated regional stratigraphic correlation, and finally explored possible directions for future work. Our extensive bibliographic reviews revealed a total of published 47 taxa, which are mostly in the form of teeth (elasmobranch) and otoliths (teleost). Skeletal specimens with taxonomic value are rare. Using Plio-Pleistocene otoliths from the famous Chochen-Tsailiao locality, we further demonstrated that they are numerous in the sediments, with high abundance and broad distribution. Study small fish remains for attaining a high resolution on the spatiotemporal dynamics of fish faunas through time and for providing the data necessary for conservational purposes is recommended.

Little is known about long-term changes in coral reef fish communities. Here we present a new technique that leverages fish otoliths in reef sediments to reconstruct coral reef fish communities. We found over 5,400 otoliths in 169 modern and mid-Holocene bulk samples from Caribbean Panama and Dominican Republic mid-Holocene and modern reefs, demonstrating otoliths are abundant in reef sediments. With a specially-built reference collection, we were able to assign over 4,400 otoliths to one of 56 taxa (35 families) though mostly at genus and family level. Many otoliths were from juvenile fishes for which identification is challenging. Richness (by rarefaction) of otolith assemblages was slightly higher in modern than mid-Holocene reefs, but further analyses are required to elucidate the underlying causes. We compared the living fish communities, sampled using icthyocide, with the sediment otolith assemblages on four reefs finding the otolith assemblages faithfully capture the general composition of the living fish communities. Radiocarbon dating performed directly on the otoliths suggests that relatively little mixing of sediment layers particularly on actively accreting branching coral reefs. All otolith assemblages were strongly dominated by small, fast-turnover fish taxa and juvenile individuals, and our exploration on taxonomy, functional ecology and taphonomy lead us to the conclusion that intense predation is likely the most important process for otolith accumulation in reef sediments. We conclude that otolith assemblages in modern and fossil reef sediments can provide a powerful tool to explore ecological changes in reef fish communities over time and space.

Dongsha Island, situated in the northern part of the South China Sea, is surrounded by coral reefs and deep-sea habitats. The coastal areas of the atoll, a marine protected area, serve as important nursery habitats for many reef fish species. At the same time, the offshore deep-sea continental slopes are historically important fishing grounds. Although previous inventories primarily focused on coral reef fishes within the atoll listing 652 species from 73 families, comprehensive surveys of fishes from deeper waters have been incomplete. In this study, the species composition of the fish fauna around Dongsha was updated by analyzing large volumes of frozen bycatch from commercial deep-sea trawlers operating in the area for the past four years and reviewing the existing literature. The species list increased to 1087 species belonging to 167 families, including several documented as new records and potentially undescribed species. This updated checklist also includes images of each species and most of their sagittal otoliths. This will assist further taxonomic work and significantly enhance understanding of marine biodiversity in the South China Sea.