Age and growth of Australian grayling, Prototroctes maraena Gnnther (Salmoniformes : Prototroctidae), in the Tambo River, Victoria

Abstract

The age and growth of Australian grayling were studied in 1203 individuals collected from the Tambo River, Victoria, between January and November 1979. Scales from 667 grayling were examined. The scale method of age determination was validated by the analysis of seasonal changes in the pattern of scale growth and by correspondence between ages inferred from length-frequency distributions and ages determined by scale readings. One annulus is formed on the scale by October. Most (88%) grayling belonged to the 1+ and 2+ age-classes; fish aged 3+ and 4+ made up 11% of the collection, and fish aged 5+ less than 1%. Size increased from January until May; growth ceased during winter and resumed in September. There was no difference in growth between the sexes. The largest grayling collected was a female of 253 mm fork length (L_f). The overall length-weight relationship was W = 2 715 × 10^-6L_f^{3 2764}. The relationship between total length (L_t) and L_f was L_t = 0.93 16 + 1.0742 L_f, and between standard length (L_s) and L_f was L_s = 0.8007 + 0.9095 L_f The overall ratio of males to females was 56 : 44.