AGE COMPOSITION, GROWTH, REPRODUCTIVE-BIOLOGY, AND RECRUITMENT OF KING GEORGE WHITING, SILLAGINODES PUNCTATA, IN COASTAL WATERS OF SOUTHWESTERN AUSTRALIA

The age structure, growth and reproductive biology have been determine d for the recreationally and commercially important King George whitin g, Sillaginodes punctata, off southwestern Australia. The maximum leng ths and ages, asymptotic lengths (L-infinity), and growth coefficients (K) were 596 mm, 14 years, 532 mm, and 0.47, respectively, for female s, and 555 mm, 13 years, 500 mm and 0.53, respectively, for males. Sex ual maturity is attained by 50% of female S. punctata by ca. 410 mm in length, and by the majority of both female and male fish at the end o f their fourth year of life. The monthly trends in the proportions of mature gonads and the prevalence of different oocyte stages and postov ulatory follicles indicated that, in southwestern Australia, S. puncta ta spawns from June to September. Spawning is thus initiated when wate r temperatures are declining from their maxima. During the spawning pe riod, many of the ovaries of large fish contained yolk vesicle and yol k granule oocytes, as well as hydrated oocytes or postovulatory follic les (or both), indicating that S. punctata is a multiple spawner. Furt hermore, because hydrated oocytes or postovulatory follicles were ofte n found together with large numbers of yolk granule oocytes, S. puncta ta presumably releases eggs in batches during the spawning period. Rec ruitment of S. punctata into sheltered nearshore waters (<1.5 m) comme nces in late September, three months after the onset of spawning, and continues until early November. When juvenile S. punctata reach ca. 1. 5 years of age and ca. 250 mm, the legal minimum length for capture, t hey move out into slightly deeper waters (2-6 m) in marine embayments and estuaries. After attaining ages of ca. 4 years and lengths of ca. 370 mm, they then migrate from these waters, where fishing pressure is greatest, into regions near or around reefs at depths of 6-50 m, wher e spawning occurs. In contrast to S. punctata, the five other whiting species in southwestern Australian waters, which all belong to the gen us Sillago, spawn between late spring and early autumn. In the case of the three Sillago species that undergo an offshore migration, this mo vement occurs at a relatively small size and young age and leads to th eir occupying open sandy areas. The implications of S. punctata habita t and biological data for fishery management are discussed.