Other studies and applications

The hidden diversity of fish otoliths in traditional Chinese medicine

Fish otoliths have been used as medicine in many regions and cultures of the world. The history of using otoliths, so called "yu nao shi", in traditional Chinese medicine (TCM) can be trace back to the Song dynasty. A range of effects is reported for otoliths in TCM, including relieving nasal membrane inflammation. The source of these otoliths has been widely described as originating from the yellow croakers (Larimichthy spp., Sciaenidae), one of the intensively fished coastal fish in the waters off western Taiwan. Vendors claim efficacy only if the otoliths of yellow croakers are applied. However, our preliminary survey suggest that a wide variety of fish taxa are involved in the production of otoliths in TCM. Therefore, this project aims to describe the hidden diversity of otolith taxa that are sold as TCM in Taiwan. The significance of the study will improve the validation technique of biological product in TCM, as well as further revealing whether the specific fishery in TCM is sustainable.

The significance of fish otoliths in the archaeological midden site in Tainan City, southwestern Taiwan

As a continuation of the previously described Pomadasys otoliths from an archaeological midden site in Tainan City, southwestern Taiwan, we explore the significance of other co-occurring otolith-based fish taxa. Materials from the related sites in the area over the past 3000 yrs will be discussed together. Taxonomy composition and size frequency data will be measured, and the implication of coastal adaptation of prehistoric inhabitants will be discussed.

Application of otoliths in diet composition analysis: a case study of bigeye tuna from tropical Indian Ocean

One hundred and eighty two stomach samples of bigeye tuna Thunnus obesus were collected between April 2006 and December 2006 from three Taiwanese longline vessels in the tropical Indian Ocean. A total of 1,021 free otoliths were extracted for otolith morphology identification from 78 stomachs. The results showed that 49.46% belonged to the Myctophidae and 21.45% were Scopelarchidae, followed by Diretmidae (7.54%), Microstomatidae (5.48%), Paralepididae (5.48%) and Macrouridae (4.60%). Three newly recorded prey items, Valenciennellus tripunctulatus (Sternoptychidae), Evermannella sp. (Evermannellidae) and Zenion sp. (Zenionidae) were found. The remaining otoliths can be identified to a lower taxon, e.g. Electrona risso and Diaphus sp. for myctopid; Macroparalepis, Magnisudis, Paralepis and Sudis for paralepidid, much better than the traditional examination of stomach contents. Effects of acid erosion are also evaluated to check the morphological change of digesting otolith and found that some Diaphus specimens are less endurable. No spatio-temporal difference was found, however, a dietary shift through its growth was significant. Smaller bigeye tuna preyed mainly on Myctophidae, whereas through their growth the consumption proportion of Scopelarchidae, Paralepididae and Macrouridae increased and Myctophidae decreased.