Length and age compositions and growth rates of the Australian herring Arripis georgiana in different regions

Abstract

Arripis georgiana was collected from coastal waters in Western Australia and South Australia. The opaque zones on the otoliths were shown to be formed annually and thus their number could be used to age the individuals of this species. Although the catches of A. georgiana in south-western Australia, where spawning occurs, were dominated by the 0+ to 5+ age classes, they did contain females and males up to ten and nine years old, respectively. The von Bertalanffy growth parameters for the two sexes in this region differed significantly, with the asymptotic length (L_∞) being significantly greater for females (262 mm) than for males (239 mm), whereas the reverse was true for the growth coefficient (k), i.e. 0.813 v. 0.992. The catches of A. georgiana eastwards of 121˚44′E on the south coast of Western Australia, where spawning does not occur, were dominated by the 0+ to 2+ age classes. The above data, when taken in conjunction with earlier tagging experiments and the marked decline that occurs in the number of 2+ fish in South Australia in summer, imply that, during this period, many two-year-old individuals of A. georgiana start migrating towards their spawning areas in south-western Australia.