Age validation and growth of the small-tooth flounder Pseudorhombus jenynsii from estuaries and coastal waters in south-western Australia

Abstract

The small-tooth flounder Pseudorhombus jenynsii (Paralichthyidae) is a common, yet relatively unstudied, flatfish occurring in estuaries and coastal waters around Australia. This study determined the age and growth of P. jenynsii using 1,228 specimens collected between 2004 and 2013 as bycatch by seine netting in estuaries and trawling in coastal waters in south-western Australia. Opaque zones in 1,043 sectioned otoliths were validated as forming annually by otolith edge analysis, with the first opaque zone becoming delineated after the first spring when fish are ~ 12 months old. Female P. jenynsii ranged in total length from 79 to 406 mm and males from 96 to 354 mm. The maximum observed age for females and males was 5 and 4 years, respectively. While the von Bertalanffy growth functions (VBGF) fitted to the lengths at age differed significantly between the sexes, this difference in the length at age was < 5% between the ages of 1 and 3 years (where most of the data lay). The VBGF parameters for both sexes combined are L∞: 381 mm, k: 0.53 year−1, t0: -0.15 years. The large variation in size-at-age of P. jenynsii is indicative of a presumed extended 5–6 months spring and summer spawning period. The presence of small (< 200 mm) and young (< 2 years old) P. jenynsii in estuaries and shallow coastal waters confirms the use of these environments as nursery habitats.