Title Maturation of the Spotted Mackerel Scomber australasicus in the Waters off Ashizuri Cape, Pacific Coast of Southern Japan, with Reference to the Habitat Water Temperatures
Authers Kazuya NASHIDA and Takumi MITANI
Keywords spotted mackerel, spawning season, histology, biotelemetry, water temperature
Citation Bull. Fish. Res. Agen. supplement No. 4, 119-124, 2006
Adult spotted mackerel Scomber australasicus were caught by vertical long lines offshore of Ashizuri Cape, Pacific coast of southern Japan, from January 2000 to November 2004. The spawning seasons of this fish were examined with gonad index and histological study of the female by monthly samplings. In this area, the gonad index values rapidly increased from late February, and peaked between late February and mid March. These periods are thought to be the main spawning season, and the spawning season ends in June. By using biotelemetry system, the vertical movement pattern of spotted mackerel was also examined in the main spawning season. The fish tracked swam between the surface and 50m depth layer with frequently vertical migrations. From February to March, the water temperatures were almost the same as 17 to 18 ℃, because of the vertical mixing. In the end of the spawning season in June, the thermocline was formed at 50m depth layer and the water temperature were from 20 to 22 ℃at this layer. This range of water temperature might be the upper limit of the spawning season for the spotted mackerel.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull-b4/16.pdf