Vol. 48 No. 5, 2009

Time Series Analysis of Taiwanese Catch Data of Japanese Glass Eels Anguilla japonica: Possible Effects of the Reproductive Cycle and El Niño Events

Yu-San Han^1,*, Wann-Nian Tzeng¹, and I-Chiu Liao²

¹Department of Life Science and Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei 106, Taiwan
²Department of Aquaculture, College of Life and Resource Sciences, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 202, Taiwan

Yu-San Han, Wann-Nian Tzeng, and I-Chiu Liao (2009) The annual catch of glass eels of the Japanese eel Anguilla japonica highly fluctuates in East Asia, which is a great risk to the eel aquaculture industry and makes resource management difficult.  An analysis of data of the catch of glass eels from 1972 to 2008 in Taiwan indicated that the glass eel catch mainly fluctuates in a cycle of 5 and 6 yr, which matches the dominant reproductive cycle of this species.  The peak catch percentage of silver eels in the estuary of the Kaoping River in southwestern Taiwan occurred 1 yr before a glass eel peak catch, implying a possible spawner-recruit relationship.  Burst catches of glass eels every 11 yr match periods of maximum solar activity.  The annual glass eel catch was not statistically correlated with the El Niño-Southern Oscillation (ENSO) index, although strong El Niño events seemed to correspond to years of poor catches.  Thus, fluctuations in the annual glass eel catch are likely shaped by both the reproductive cycle of the eel and environmental variations such as sunspot cycles and strong El Niño events.

Key words: Japanese eel, Glass eel Catch, Time series analysis, Reproductive cycle, ENSO.

*Correspondence: Tel: 886-2-33663726.  Fax: 886-2-33663726.   E-mail:yshan@ntu.edu.tw