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Age composition, growth, reproductive biology, and recruitment of King George whiting, Sillaginodes punctata, in coastal waters of southwestern Australia

Hyndes, G.A., Platell, M.E., Potter, I.C. and Lenanton, R.C.J. (1998) Age composition, growth, reproductive biology, and recruitment of King George whiting, Sillaginodes punctata, in coastal waters of southwestern Australia. Fishery Bulletin, 96 (2). pp. 258-270.

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Abstract

The age structure, growth and reproductive biology have been determined for the recreationally and commercially important King George whiting, Sillaginodes punctata, off southwestern Australia. The maximum lengths and ages, asymptotic lengths (L∞), and growth coefficients (K) were 596 mm, 14 years, 532 mm, and 0.47, respectively, for females, and 555 mm, 13 years, 500 mm and 0.53, respectively, for males. Sexual 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 of their fourth year of life. The monthly trends in the proportions of mature gonads and the prevalence of different oocyte stages and postovulatory follicles indicated that, in southwestern Australia, S. punctata spawns from June to September. Spawning is thus initiated when water temperatures are declining from their maxima. During the spawning period, many of the ovaries of large fish contained yolk vesicle and yolk granule oocytes, as well as hydrated oocytes or postovulatory follicles (or both), indicating that S. punctata is a multiple spawner. Furthermore, because hydrated oocytes or postovulatory follicles were often found together with large numbers of yolk granule oocytes, S. punctata presumably releases eggs in batches during the spawning period. Recruitment of S. punctata into sheltered nearshore waters (<1.5 m) commences 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, they 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, where spawning occurs. In contrast to S. punctata, the five other whiting species in southwestern Australian waters, which all belong to the genus Sillago, spawn between late spring and early autumn. In the case of the three Sillago species that undergo an offshore migration, this movement occurs at a relatively small size and young age and leads to their occupying open sandy areas. The implications of S. punctata habitat and biological data for fishery management are discussed.

Publication Type: Journal Article
Murdoch Affiliation: School of Biological and Environmental Sciences
Publisher: US National Marine Fisheries Services
URI: http://researchrepository.murdoch.edu.au/id/eprint/18450
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