Zoological Studies

Vol. 51 No. 4, 2012

Migration Behavior and Habitat Use by Juvenile Japanese Eels Anguilla japonica in Continental Waters’ as Indicated by Mark-Recapture Experiments and Otolith Microchemistry

Shih-Huan Lin1, Yoshiyuki Iizuka3, and Wann-Nian Tzeng1,2,4,*

1Institute of Fisheries Science, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 106, Taiwan
2Department of Life Science, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 106, Taiwan
3Institute of Earth Science, Academia Sinica, Taipei 115, Taiwan
4Department of Environmental Biology and Fisheries Science, National Taiwan Ocean University, Keelung 202, Taiwan

Shih-Huan Lin, Yoshiyuki Iizuka, and Wann-Nian Tzeng (2012) The migratory behavior of Japanese eels Anguilla japonica in continental waters was examined by a mark-recapture experiment with 3263 wild and marked culture-originating yellow eels. The experiment was conducted in Dapong Bay and the Kaoping River estuary in southwestern Taiwan over a 4-yr period in 2003-2006. The migratory environmental history of the marked and wild eels was reconstructed by examining temporal changes in otolith strontium (Sr)/calcium (Ca) ratios by an electron probe micro-analysis (EPMA). Otolith Sr/Ca ratios of recaptured eels indicated that juvenile yellow eels preferred a brackish environment similar to the wild population. Otolith Sr/Ca ratios revealed that estuarine contingents were higher in both the river (75.5%) and bay (60%) than were freshwater contingents (river, 22%; bay, 25%) and seawater contingents (river, 2.5%; bay, 15%). The recapture rate of marked eels sharply decreased with increasing distance from the release site, and the maximum dispersal distance of eels was < 2 km, indicating that the eels may exhibit territorial behavior after recruitment to the river. The recapture rate also sharply decreased with time, indicating that heavy harvesting of eels occurred in a short time after release. The specific habitat use and limited home range suggest that eels could easily be subjected to overfishing, which should be considered when planning conservation and fisheries management policies.

Key words: Anguilla japonica, Habitat use, Migratory behavior, Otolith Sr/Ca ratios, Mark-recapture.

*Correspondence: Tel: 886-2-33662887. Fax: 886-2-23639570. E-mail:wnt@ntu.edu.tw