Geometric morphometric discrimination between seven populations of Kawakawa Euthynnus affinis (Cantor, 1849) from Peninsular Malaysia

Abstract

Small epipelagic and migratory, Euthynnus affinis (kawakawa) is one of the commercially significant tunas of Indo-Pacific tropical and subtropical waters. Unfortunately, the management and stock structure of certain migratory species in the area is not clear. The current study aimed to discriminate the E. affinis through shape and body size variations and to evaluate the variations among seven populations of E. affinis. A total of 114 individuals of E. affinis were collected from two main geographic areas; the Straits of Malacca and the South China Sea. Multivariate analyses, such as discriminant function analyses (DFA) and principal component analyses (PCA) of 11 homologous landmarks and seven morphometric variables were carried out to discriminate seven populations of E. affinis. The results revealed a significant variations among the body shape of the seven populations of E. affinis. Morphological homogenous occurred between populations obtained from the east coast of Peninsular Malaysia (Terengganu, Kelantan, and Johor). However, populations found on the west coast of Peninsular Malaysia (Selangor) were separated and formed another cluster. The variations in the body shape of E. affinis occurred in the body depth and the overall body shape. The percentage of overall correct classification for all seven populations of E. affinis is 88.6%. This present study is the first report using a geometric morphometric method performed on the E. affinis from Peninsular Malaysian waters.