Vol. 50 No. 3, 2011

Reproductive Biology of the Needlefish Tylosurus acus melanotus in Waters around Hsiao-Liu-Chiu Island, Southwestern Taiwan

Yih-Yia Liao* and Yu-Hsin Chang

Department of Fishery Production and Management, National Kaohsiung Marine University, Kaohsiung 811, Taiwan

Yih-Yia Liao and Yu-Hsin Chang (2011) In this study, we investigated the reproductive biology of the needlefish Tylosurus acus melanotus in waters of Hsiao-Liu-Chiu off southwestern Taiwan. In total, 658 specimens (329 females and 329 males) were collected monthly from driftnet catches in July 2008-Aug. 2009. Relationships between the eye fork length (EFL) and body weight (BW) did not significantly differ between sexes. Oocyte development was categorized into 8 stages based on histological examinations. The spawning season extended from Apr. to Aug. based on the macroscopic appearance of the gonads, a histological examination of the ovaries, estimations of the gonadosomatic index, and the frequency of oocyte diameters. Sizes at 50% maturity were respectively estimated to be 56.8 and 53.3 cm in EFL for females and males. The sex ratio did not significantly differ from 0.5 according to a Chi-squared test (p > 0.05). The mean fecundity of this species was estimated to be 25,629 ± 6902 eggs. The batch fecundity was estimated to be in the range of 1062-24,576 eggs with a mean of 5748 ± 4670 eggs.

Key words: Reproductive biology, Tylosurus acus melanotus, Hsiao-Liu-Chiu, Southwestern Taiwan.

*Correspondence: Tel: 886-7-3617141 ext. 3519. Fax: 886-7-3628844. E-mail:yihyia@mail.nkmu.edu.tw