Abstract
In this study, we analyzed the stomach content of two individuals of rare, young Russell’s oarfish, Regalecus russelii, from Taiwan. One of them was captured alive along with larval fish and crustaceans by a stow net from the shallow waters (15-18m deep) of the Tamsui River mouth. A total of 38 individuals of larval fish belonging to three species (86.4% of all prey) and 6 individuals of crustaceans belonging to three species were found in the Russell’s oarfish specimen’s stomach. Among the prey, the Japanese anchovy (Engraulis japonicus) was the most dominant fish species, accounting for 44.7% of all fishes; and luciferids were the most dominant crustaceans, accounting for 66.7% of all crustaceans. All the prey fish were sandy or a mixture of sandy and muddy sediment dwellers. The luciferids and Japanese anchovies are characterized by having diel vertical migration behavior. Based on the sampling information and biological characteristics of the fish larvae and crustaceans, we conjectured that the abundance of these prey when they moved up to the upper layer of the Tamsui River mouth at nighttime had attracted the young Russell’s oarfish to hunt there. In addition, we speculated that it might be easier for the vertical-swimming Russell's oarfish to hunt a large number of luciferids assembled in the upper layer of the water by its particular posture or angle of view.
References
Benfield, M.C., Cook, S., Sharuga, S. & Valentine, M.M. (2013) Five in situ observations of live oarfish Regalecus glesne (Regalecidae) by remotely operated vehicles in the oceanic waters of the northern Gulf of Mexico. Journal of Fish Biology, 83, 28–38. https://doi.org/10.1111/jfb.12144
Chen, I-S. & Fang, L.-S. (1999) The freshwater and estuarine fishes of Taiwan. The Preparatory Office of National Museum of Marine Biology & Aquarium Press, Pingtung, 287 pp. [in Chinese]
Chung, K.-F. & Shao, K.-T. (2022) Catalogue of life in Taiwan. Web electronic publication. version 2022. Center for Digital Cultures and Biodiversity Research Center, Academia Sinica, Taiwan. Available from: http://taibnet.sinica.edu.tw/ (accessed 7 June 2022)
Cuvier, G. (1816) Le Règne Animal distribué d'après son organisation pour servir de base à l'histoire naturelle des animaux et d'introduction à l'anatomie comparée. Les reptiles, les poissons, les mollusques et les annélides. Edition 1. v. 2, i–xviii + 532 pp.
Feeney, R.F. & Lea, R.N. (2018) California records of the oarfish, Regalecus russelii (Cuvier, 1816) (Actinopterygii: Regalecidae). Southern California Academy of Sciences, 117, 169–179. https://doi.org/10.3160/3294.1
Forsgren, K.L., Jamal, H., Barrios, A. & Paig-Tran, E.W.M. (2017) Reproductive morphology of oarfish (Regalecus russellii). Anatomical Record, 300, 1695–1704. https://doi.org/10.1002/ar.23605
Heemstra, P.C. (1986) Regalecidae. In: Smith, M.M. & Heemstra, P.C. (Eds.), Smith’s sea fishes. Springer, Berlin,
Honma, Y., Ushiki, T., Hashizume, H., Takeda, M., Misaki, H., Inagi, A. & Ishibashi, T. (2004) Histological observations on the ovaries of two species of Taeniosomatous fishes (Lampridiformes) caught in waters adjacent to the Japanesemain island. Publications of the Seto Marine Biological Laboratory, 40, 113–120. https://doi.org/10.5134/176314
Lee, M.-A. (2004) Bycatch of larval anchovy fishery in the coastal waters of Taiwan. Bulletin of Taiwan Fisheries Research Institute, 5, 93–101.
Lin, C.-M. (1999) A study on community structure of larval fishes in I-LAN Bay. Department of Science Education, National Taipei University of Education, Master thesis, Keelung.
Ma, J.-P. (1998) Spatial and Temporal Variabilities of Euphausiids and Lucifers in the Waters Southwest of Taiwan. Institute of Marine Biology, National Sun Yat-sen University, Master thesis, Kaohsiung. [in Chinese]
Moyle, P.B. & Cech, Jr J.J. (2004) Fishes, an introduction to ichthyology. Prentice Hall, Upper Saddle River, NJ.
Nakabo, T. (2002) Fishes of Japan with pictorial keys to the species, English edition I. Tokai University Press, Tokyo, 1749 pp.
Nelson, J.S., Grande, T.C. & Wilson, M.V. (2016) Fishes of the world. John Wiley & Sons, 752 pp. https://doi.org/10.1002/9781119174844
Nishimura, S. (1960) A record of Regalecus russellii (SHAW) from the Sado Straits in the Japan Sea. Annual Report of the Japan Sea Regional. Fisheries Research Laboratory, 6, 58–68.
Okiyama, M. (1988) An atlas of the early stage fishes in Japan. Tokai University Press, Tokyo, 1154 pp.
Palmer, G. (1986) Regalecidae. In: Whitehead, PJ.P., Bauchot, M.L., Hureau, J.C., Nielsen, J. & Tortonese, E. (Eds.), Fishes of the north-eastern Atlantic and the Mediterranean. UNESCO, Paris, pp. 727–728. https://doi.org/10.2307/1444931
Roberts, T.R. (2012) Systematics, biology, and distribution of the species of the oceanic oarfish genus Regalecus (Teleostei, Lampridiformes, Regalecidae). Mémoires du Muséum national d'histoire naturelle Tome 202, Paris.
Shao, K.-T. (2022) Taiwan Fish Database. WWW Web electronic publication. Center for Digital Cultures and Biodiversity Research Center, Academia Sinica, Taiwan. Available from: http://fishdb.sinica.edu.tw/ (accessed 26 April 2022)
Shih, Y.-M. (2013) Short-term variations in larval fish community and relations in sampling designs – a case study in Tamsui River estuary, northern Taiwan. Institute of Oceanography, National Taiwan University, Master thesis, Taipei. [in Chinese]
Sivadas, M. & Bhaskaran M. (2009) Stomach content analysis of the Indian mackerel Rastrelliger kanagurta (Cuvier) from Calicut, Kerala. Indian Journal of Fisheries, 56 (2), 143–146.
Voesenek, C.J., Muijres, F.T. & van Leeuwen, J.L. (2018) Biomechanics of swimming in developing larval fish. Journal of Experimental Biology, 221, 1, jeb149583. https://doi.org/10.1242/jeb.149583
Wang, Y.-T. (1997) Studies of immigratory dynamics and early life histories of larval clupeoids in the coastal waters off Tanshui River estuary. Department of Zoology, National Taiwan University, Ph.D. dissertation, Taipei. [in Chinese]
Wang, Y.-T. & Tzeng, W.-N. (1997) Temporal succession and spatial segregation of clupeoid larvae in coastal waters off the Tanshui River estuary, northern Taiwan. Marine Biology, 129, 23–32. https://doi.org/10.1007/s002270050142