Studies on the Population Structure of Swordtip (Loligo edulis) and Mitre (Loligo chinensis) Squids by Using Morphometric Method

• Main Authors: Tsung-Yu Liu, 劉宗祐
• Other Authors: Cheng-Hsin Liao
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/93772949372680723414

碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 93 === The aim of this study analyzed the population structure between Swordtip squid (Loligo edulis) and Mitre squid (Loligo chinensis) by using univariate and multivariate morphometric methods in the waters around Taiwan. A total of 18 morphometric characters were measured by the 749 specimens of squid, which were collected from the waters off northeastern Taiwan, Penghu and Hsingtsu regions. Base on the morphometric characters data, the principle components analysis showed that both of L. edulis and L. chinensis did not exhibit the sexual dimorphism. In the 18 indices, only A3/ML and A4/ML were not significant difference between the L. edulis in the waters off northeastern Taiwan and the L. chinensis in the waters around Penghu, 8 indices (W/ML, HL/ML, A2/ML, A3/ML, A4/ML, FCL/GL, NCL/GL and GW/GL) were not significant difference between the L. edulis in the waters off northeastern Taiwan and the L. chinensis in the waters off Hsingtsu; and only FL/ML and A3/ML were not significant difference between the waters off Penghu and Hsingtsu but they are the same L. chinensis species. The result of relative growth showed the L. chinensis in the waters off Hsingtsu is more different from the L. chinensis in the waters off Penghu than the L. edulis in the waters off northeastern Taiwan. In total, 13 morphometric characters were selected by using the stepwise discriminant analysis and the discriminant functions had 84.65% correct rate among three region specimens. While, the standard coefficients of the canonical discriminant analysis in the HW, MOW and FW were more different than others. The results of the cluster analysis were the same with canonical discrimanant analysis, the morphometric characters in the waters off Penghu and Hsinghu were more similarity than in the waters off northeastern Taiwan. In addition, the stepwise discriminant analysis selected 11 morphometric characters of the L. edulis specimens from different fishing ground (Area 1, Area 2 and Area 3) in the waters off northeastern Taiwan. Based on these 11 variables, the discriminant functions could permit 79.08% correct rate among the three area specimens. The results of the cluster analysis and canonical discriminant analysis showed the morphomertic characters of the Area 2 are more different than Area 1 and Area 3. From the frequency of ML in three areas showed that the 75% specimens in Area 2 (ocean front fishing ground) were the mid-size squid (ML between 70 and 130mm), which were the mature and immature squids. However, the squids in Area 3 (upwelling fishing ground) were the small- and large-size, which were the nursing and spawning squids. These results indicated that the squid in order to suit the life cycle in different marine environment and caused the changes of morphometric characters.