Demographic characteristics of an Antarctic plunderfish, Harpagifer bispinis antarcticus

Abstract

H. b. antarcticus Nybelin is a relatively long-lived, slow-growing fish inhabiting shallow-water embayments on the Antarctic Peninsula. Age of 153 fishes taken between March and Dec., 1975 in Arthur Harbor, Anvers Island, was determined from otoliths. Growth rates were estimated from annuli back-calculation and using a Brody-von Bertalanffy model. Nine year old fish were collected; annual growth increments ranged between 4-10 mm for both sexes. Growth curves of the Arthur Harbor population were similar between the sexes but differed from those of a population in Paradise Harbor. Survivorship for males and females was high, .apprx. 75%; instantaneous mortality averaged 0.25 for females and 0.22 for males. Population structure appeared stable through the sample period; recruitment of 3 yr old fish was most common in late autumn-early winter. Formation of the annulus occurs during the austral winter, at the same time these fish spawn, and may be associated with this event rather than decreased feeding or activity.