Morphological differences between cultivated and wild jack mackerel Trachurus japonicus.

Abstract

Morphological differences between the cultivated and the wild Japanese jack mackerel, Trachurus japonicus are examined as a part of obtaining knowledge on the degree of the intra-specific variation of T. japonicus and in order to find out what kind of morphological variations appear under the cultivated condition. Comparisons were made for the 31 cultivated and 43 wild (from southwestern Shikoku) fish and the 31 cultivated and 1181 wild (various parts of Japan) fish. 16 morphometric characters were examined. In the cultivated T. japonicus, the body depth becomes large and the pectoral fin shortens. These are remarkable external morphological changes seen in both comparisons.These morphological changes may occur in the spatially limited environment like fish cultiva-tion, because the fish activity is restricted in comparison with that in the natural environment.