Regional variations in growth of Jack mackerel Trachurus japonicus in the waters off the Pacific coast of Japan

Abstract

We investigated the age and growth of jack mackerel Trachurus japonicus collected in five areas in the sea along the Pacific coast of Japan: Uwa Sea, Kii Channel, Kumano-nada Sea, Sagami Bay, and Joban–Boso area, between 2011 and 2014. Fish were age-determined using transverse sections of sagittal otoliths. Fork length-at-ages were estimated by von Bertalanffy growth function and were compared among the areas. Fish growth in Uwa Sea was fastest among the five areas, while that in the Joban–Boso area was slowest, and those in Kii Channel, Kumano-nada Sea, and Sagami Bay were approximately intermediate between the southwestern area of Uwa Sea and the northeastern area of the Joban–Boso area. In the five areas, most fish were between 1 and 3 years old. No fish older than 9 years occurred in the Uwa Sea, while fish older than 15 years occurred in Sagami Bay and the Joban–Boso area. Fish growth was slower in areas with a longer cool season with sea temperatures lower than 18°C.