Zoological Studies

Vol. 45 No. 4, 2006

Spawning Frequency and Batch Fecundity of the Sailfish (Istiophorus platypterus) (Istiophoridae) in Waters off Eastern Taiwan

Wei-Chuan Chiang1,2, Chi-Lu Sun1,*, Su-Zan Yeh1, Wei-Cheng Su3, and Don-Chung Liu3

1Institute of Oceanography, National Taiwan University, Taipei, Taiwan 106
2Present address: Eastern Marine Biology Research Center of Fisheries Research Institute, Council of Agriculture, Executive Yuan, Taitung, Taiwan 961
3Fisheries Research Institute, Council of Agriculture, Executive Yuan, Keelung, Taiwan 202

Wei-Chuan Chiang, Chi-Lu Sun, Su-Zan Yeh, Wei-Cheng Su, and Don-Chung Liu (2006) The sailfish (Istiophorus platypterus) (Istiophoridae) is widely distributed in tropical and temperate oceans of the world. In Taiwan, sailfish are abundant from Apr. to Oct. (with the peak abundance from May to July) and substantially contribute to the economy of the east coast of Taiwan. In this study, we estimated the spawning frequency and batch fecundity of female sailfish off eastern Taiwan based on histological examinations of the ovaries of 246 sailfish collected at the Shinkang Fish Market in eastern Taiwan between Jan. 1999 and Sept. 2000. The proportion of mature females with ovaries containing postovulatory follicles was 0.53 on average during the spawning season of Apr. to Sept., suggesting that on average, the sailfish spawns every 1.89 d. Sailfish are multiple spawners with asynchronous oocyte development. Batch fecundity for 18 females with the presence of hydrated oocytes but without postovulatory follicles yielded (0.2-2.48) x 106 eggs with an average of 1.3 x 106 eggs. The relationships between batch fecundity in millions (BF) versus round weight (RW, in kg) and lower jaw fork length (LJFL, in cm) are BF = 0.0944 x RW - 1.3134 (r2 = 0.724) and BF = 5.46 x 10-5 LJFL6.283 (r2 = 0.667), respectively.

Key words: Sailfish, Spawning frequency, Batch fecundity, Postovulatory follicles, Hydrated oocytes.

*Correspondence: Tel and Fax: 886-2-23629842. E-mail:chilu@ntu.edu.tw