2017 Volume 81 Issue 1 Pages 18-28
Age, growth, maturity and food habits of spotted mackerel Scomber australasicus caught at the Emperor Seamounts from 2008 to 2015 by bottom trawl fishing vessels were examined. Fork length (FL) ranged from 211.1 to 443.5 mm FL. Ages were estimated from 0–9 years by scale reading. The von Bertalanffy growth formula based on the age-FL relationship was expressed as FLt=432.7×(1-exp(-0.24(t+2.59))), where FLt is the FL (mm) at t (year). Seasonal changes in the gonad-somatic index suggested that the spawning period extended from March to July. Stomach contents analysis showed that the major prey organisms were Euphausiidae, Decapodiformes, Thecosomata, Salpidae, Pyrosomatidae and Piscese. The year-class in 2008 was the most dominant and clear recruitments of other yearclasses were not found. Since previous surveys reported high egg production of spotted mackerel around southern waters off Hachijo-jima in the Izu islands in 2008, it is likely that individuals spawned in these waters were transported to the Emperor Seamounts by the Kuroshio and Kuroshio Extension.
