International eel symposium, 2003 - Quebec August 11, 2003
Oral Presentation

Variability in Growth Rate and Age at Maturity of American Eels (Anguilla rostrata) Transplanted from North America to Tropical Taiwan

Tzeng, W.-N.* Department of Zoology, College of Science, National Taiwan University, Taipei, Taiwan 106, ROC. wnt@ccms.ntu.edu.tw

Presenter email address: wnt AT ccms.ntu.edu.tw

Abstract Text: Six exotic silver American eels Anguilla rostrata (LeSueur) were found in the natural waters of Taiwan. They were introduced from North America as elvers to supplement an insufficient supply of the Japanese eel elver for aquaculture in Taiwan. The growth rate of these eels and their age at maturity (metamorphosis from yellow to silver stage) were compared with those of Japanese eels in Taiwan and American eels in Canada. The mean length and weight of the exotic American eels at maturity was significantly greater than for American eels in Canada (p<0.01), but similar to that of Japanese eels in Taiwan, irrespective of sexes. In contrast, the age of the exotic American eels at maturity was significantly less than for Japanese eels in Taiwan and American eels in Canada (p<0.01). The difference in age at maturity between exotic American eels and Japanese eels may be due to the delayed spawning migration of the exotic eel resulting from a failure in migration orientation as indicated from the otolith Sr/Ca ratio life history scan. The age at maturity was significantly negatively correlated with growth rate but the correlation between length (weight) and age at maturity was not significant (p>0.05). This study demonstrates an allopatric and a sympatric evolution in the growth performance of congeneric freshwater eel species.