Title: A preliminary study on biological characteristics of chub mackerel(Scomber japonicus) spawning stock in central Taiwan Strait
Abstract: According to the biological data and fecundity count of chub mackerel(Scomber japonicus) collected from central Taiwan Strait in spring,2010,the biological characteristics of the spawning stock were studied. The results show that the male to female ratio of the spawning stock was 1∶ 1. The fork length of the stock ranged from 212. 00 mm to 271. 00 mm with an average value of 244. 76 mm,and the dominant group ranged from 230. 00 mm to 260. 00 mm. The minimum fork length of the maturity was 225. 00 mm and 221. 00 mm for female and male fish,respectively. Body weight ranged from 110. 99 g to 242. 00 g with an average of 170. 97 g and the dominant group ranged from 130. 00 g to 220. 00 g. The dominant individual gonad maturities were in stage of Ⅳ and Ⅴ for both male and female fish. The feeding intensity was 2. 00 for female and 2. 25 for male fish,which is higher. The average feeding intensity declined with the improvement of gonad maturity for female fish,while the reverse is true for males. Before reached full sexual maturity,GSI of both male and female fish increased with the gonad development. GSI of female fish was slightly higher than that of male fish. The absolute fecundity was 5. 283 5 × 104~ 16. 884 7 × 104 grains with an average value of(10. 405 0 ± 0. 611 8) × 104grains. The relative fecundity with fork length ranged from 227 to 625 grain / mm with an average value of 423 ± 22 grain / mm. The fecundity is increasing with the fork length. The fecundity increased sharply for fish with fork length over 250. 00 mm in contrast to the fork length less than 250. 00 mm. Compared with the data from 1980's,the major sexual maturity age has advanced from 2 years to 1 year. The minimum sexual maturity age became the major sexual maturity age. The age composition of spawning population has changed from 1 ~ 5 years to 1 ~ 2 years and the dominant group decreased from 2 ~ 3 years to 1 year. The average fecundity of spawning population has decreased by 33. 23%. Therefore,we should formulate a reasonable minimum capture fork length at first and at the same time take measures to prohibit the fishing in spring spawning season and establish protected areas in important spawning grounds in order to protect the resources and increase the population sizes and age structure of the fish.
Publication Year: 2014
Publication Date: 2014-01-01
Language: en
Type: article
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