Morphological variation between populations of spotted mackerel (Scomber australasicus) off Taiwan

Abstract

Multivariate allometric coefficients and size-adjusted shape were estimated and compared to elucidate the stock structure of spotted mackerel (Scomber australasicus) off Taiwan. Five samples were collected separately from the south of the East China Sea (ECS), the coastal waters of Taiwan (Tashi, Taitung and Kaohsiung) and the north of the South China Sea (SCS). Fourteen morphometric measurements were made for each individual. The first eigenvector obtained from the covariance matrix of log-transformed data was used to represent the multivariate allometric coefficients. Allometric method was used to obtain size-adjusted shape data. The cluster analysis, discriminant analysis, canonical variate analysis and permutation test was used to discriminate among samples. Results indicated that (1) five areas were clustered into three distinct groups; the first group included ECS, Tashi, and Taitung; the second one included SCS; the third one included Kaohsiung, and (2) differences of allometric coefficients and size-adjusted shape in each pair of three groups are all significant. Therefore, we concluded that there are three morphologically distinguishable stocks of spotted mackerel off Taiwan. One stock is distributed in the south of the East China Sea and the coastal waters of eastern Taiwan, another is in the coastal waters off Kaohsiung, and the other is in the north of the South China Sea. The utility of morphometric measurements for discriminating stock of spotted mackerel is demonstrated, but further verification of the stock structure may be essential.