The trophic ecology of Taiwanese deep-sea sharks through stable isotopes analysis

The study of the deep-sea is rendered difficult by its hard accessibility. The shark species living down there are elusive ones, difficult to obtain alive and can not be maintained alive in aquaria for an extanded period of time. Because of all these factors, the main method used to study deep-sea sharks diet is the analysis of their stomach contents. However, such analyses present limitations: only recent preys are found, there is a bias in function of tissues digestive rates and deep-sea sharks stomachs have a relatively high probability of being empty. Stable isotope analyses are considered interesting to help resolve deep-sea sharks’ trophic ecology. We obtained deep-sea sharks with the help of fishers in Taiwanese waters. A total of five species were collected (Danea profundorum, Etmopterus brachiurus, Etmopterus molleri, Galeus sauteri, Squaliolus aliae). Muscle and liver samples were collected together with the stomachs. The analyses of the stable isotopes 13C, 15N and 34S were combined with stomach contents identification in order to obtain the isotopic niche of each sepcies and other ecological data. Species of potential preys for the six shark species were also collected in an attempt to use a mixing model in order to establish the trophic levels of the sharks