碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 100 / Jack mackerel (Trachurus japonicus) widely distributed from East China Sea and the coastal waters of Japan, Korea, and Taiwan, is an important fishery resource in the northeastern Taiwan. In recent years, rapid developing of Taiwanese seiner fishery, a new fishing gear, the catch and proportion of jack mackerel increased significantly. However, the age and growth parameters for jack mackerel were very old and catch-at-age composition is poorly known. In this study we collected otolith samples from jack mackerel catch (May, 2010 to April, 2011) for age determination. We also included the length and weight data from March, 2009 to January, 2012 to understand catch-at-age of jack mackerel in the northeastern waters off Taiwan. This study has following findings:
1. The relationship between fork length (FL) and body weight (BW) of jack mackerel were significantly different for females and males. The length-weight relationships were BW=3.6×10-2×FL2.6771 for females, and BW=3.2×10-2×FL2.7108 for males.
2. The formations of opaque zones were estimated during January to February and the ring formed once per year. The maximum age observed from the samples was 5 years (FL=32.4 cm) and minimum was 0 year (FL=14.3 cm). The parameters of von Bertalanffy growth function obtained for combined sex was L∞=40.4 cm, k=0.223 yr-1.
3. The major cohorts utilized of jack mackerel in the northeastern waters off Taiwan were 0-age (39%) and 1-age (38%). Most of them were in immature stage. The proportion of catch for 0-age was higher in winter comprising of 42~77%. The proportion of 0-age was low in summer only comprising of 3~10%.
The growth of jack mackerel in the northeastern waters off Taiwan was much slower than those in Japan waters. Further study is needed to clarify its relationship with the two stocks in Japan waters. The age composition indicated that the percentage of immature jack mackerel utilized in northeastern Taiwan were considerably high. Meanwhile, the stock abundance of spotted mackerel has being declined for many years. It is recommended to implement adequate closure measures during spawning period and catch restriction to reduce fishing mortality of young fish, which will be helpful for sustainable utilization of mackerel and carangid fish resources in the northeastern waters off Taiwan.
| Identifer | oai:union.ndltd.org:TW/100NTOU5451008 |
| Date | January 2012 |
| Creators | Chih-Chun Chen, 陳治君 |
| Contributors | Hsueh-Jung Lu, 呂學榮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 88 |
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