Zoological Studies

Vol. 42 No. 2, 2003

Early Life History Traits of Japanese Anchovy in the Northeastern Waters of Taiwan, with Reference to Larval Transport

Chih-Shin Chen and Tai-Sheng Chiu*

Department of Zoology, National Taiwan University, Taipei, Taiwan 10764

Chih-Shin Chen and Tai-Sheng Chiu (2003) There is controversy concerning the location of spawning sites and recruiting routes of Japanese anchovy in the northeastern Taiwan. Early in the larval fish fishery season, we conducted a survey along a presumptive coastal current to Ilan Bay with the aim of obtaining anchovy larvae for demographic analysis. The obtained samples of the Japanese anchovy, Engraulis japonicus, were analyzed to elucidate the species' directional tendency, which was from offshore to inshore, and which reached coastal Ilan Bay along the western boundary of the Kuroshio Current during late April. Demographic analysis indicated that offshore anchovy larvae had the smallest body size, and that the size increased from offshore toward the coastal. Based on the sagittal microstructural analysis, detailed early life history traits, such as increment size, standard length and body weight at daily ages were back-calculated, then various relationships were estimated, and significant differences were shown to have an offshore-coastal tendency. Estimated developmental stability exhibited highest variation in transitional inshore area and lowest variation in coastal area. The mean daily growth rate in standard length was 0.28 mm d-1 for larvae in the offshore area and 0.54 mm d-1 for those in the coastal area. However, the inshore larval population exhibited a non-steady growth pattern, which was 0.27 mm d-1 corresponding to an offshore environment during a period of 7-24 April, but had a subsequent higher growth rate of 0.59 mm d-1, whose value was similar to that of the coastal population. These findings combined with local flow pattern and sea surface temperature images support the hypothesis that anchovy larvae are transported from offshore at Pangaiyu to the coastal area of the Ilan Bay, along with a previously identified coastal current in northeastern Taiwan waters. Coastal area of Ilan Bay serves as an important nursery ground for late anchovy larvae.

Key words: Otolith microstructure, Daily growth, Development instability.

*Correspondence: Tel: 886-2-23630231 ext. 2128. Fax: 886-2-23634014. E-mail: tschiu@ccms.ntu.edu.tw