碩士 / 國立中山大學 / 海洋科學系研究所 / 106 / Reproductive variables (e.g., sex ratio, length and age at sexual maturity, spawning season) of commercially important fishes are frequently used for stock assessment and fisheries management purposes.This study reports the reproductive variables of two commercially important croakers, Chrysochir aureus and Otolithes ruber, in the waters off southwestern Taiwan. We collected a total of 519 C. aureus and 330 O. ruber specimens at fish markets in southwestern Taiwan from November 2012 to November 2017. For both croaker species, the results from measuring BW and L exhibited no significant differences in the BW-L relationships between males and females. The BW-L relationships was BW=0.0058TL3.184 (n=518, R2=0.99) for C. aureus and BW=0.0055TL3.206 (n=328, R2=0.98) for O. ruber. There was only a significant difference in sex ratio among the O. ruber samples in favor of females. The length estimated for 50% of sexually mature C. aureus females was 26.3 cm, which was greater than the length for sexually mature O. ruber females (21.8 cm). The age estimated for 50% of the C. aureus females was 8.6 months earlier than the time interval for the O. ruber females, which was 11.2 months. For both species, the size at 50% sexually maturation of males was smaller than females. The length estimated for 50% of sexually mature C. aureus males and O. ruber males were 21.0 cm and 19.9 cm, respectively. The histological examination results suggest that both species are multiple spawners and have dissimilar spawning seasons. The C. aureus primarily spawn from July to December, whereas the O. ruber primarily spawn from April to July. The mean batch fecundity (±SD) and relative mean batch fecundity (±SD) for C. aureus were 141,763±26,750 eggs/individual and 328±97 (eggs/ovary-free body weight), while for O. ruber were 213,217 eggs/individual and 704 (eggs/ovary-free body weight). Besides banning trawling fisheries in 3 nautical miles, the author also suggests regulating the gill net usage during the spawning seasons (May–July) around the spawning ground, in order to insure the sustainable resources use of C. aureus and O. ruber.
| Identifer | oai:union.ndltd.org:TW/106NSYS5276012 |
| Date | January 2018 |
| Creators | Hsiao-Yuan Ni, 倪小媛 |
| Contributors | Meng-Hsien Chen, 陳孟仙 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 0 |
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