Two types of Japanese jack mackerel Trachurus japonicus of summer spawning group in the Sagami Bay region.

Abstract

Larger individuals of Trachurus japonicus of the summer spawnlng group in the Sagami Bay region have been distinguished into two types, 'nodoguro' and 'maaji' by fishermen, etc. These two types were compared morphologically. There are no significant differences between them for each of nine meristic characters (t-test, p>0.05). Sixteen morphometric characters and the fork length were examined by covariance analysis. In head length, eye diameter, upper jaw length, length from the snout to the origin of unpaired fins, head depth, pectoral fin length and height of anterior scutes, nodoguro type is larger than maaji. While in body depth, length of fin bases and length of posterior part of lateral line, maaji type is larger than nodoguro type.