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Aspects of the Reproductive Biology of Murray Cod, Maccullochella peelii peelii Stuart J. Rowland NSW Fisheries, Inland Fisheries Research Station, Narrandera NSW 2700; present address, Grafton Research Centre, PMB 3, Grafton NSW 2460 Rowland, S.J. (1998). Aspects of the reproductive biology of Murray cod, Maccullochella peelii peelii. Proceedings of the Linnean Society of New South Wales 120, 147-162. Aspects of reproduction in Murray cod, Maccullochella peelii peelii, in NSW tribu-taries of the Murray-Darling river system were studied. Murray cod has a distinct seasonal cycle; monthly gonadosomatic indices (GSI) and mean oocyte diameters were low between December and March, increased rapidly from June, presumably due to vitellogenesis, and were highest in October. Oocytes underwent group-synchronous development, but only one batch of yolky oocytes was spawned during the 4-5 week breeding season. Absolute fecundi-ty ranged from 6,800 (total length, TL 480mm, weight 2.1kg) to 86,600 (1050mm, 22.7kg) eggs, and relative fecundity ranged from 3.2 to 7.6 eggs/g. Spawning was induced by a rise in water temperature to or above 20°C in spring. The presence of many consecutive year classes suggests that Murray cod spawn annually; however, between 1977 and 1980 relatively strong year classes were formed only in rivers that were at, or near flood levels during the breeding season. No females and a few males had matured by 3 years of age. At 4 years of age, 77% of females (> 480mm, 2.1kg) and 72% of males (> 530mm, 2.3kg) were mature. All females and most males were mature at 5 years. In rivers, all cod larger than 590mm and 3.9kg were mature, but the smallest sexually-mature cod sampled from the impoundment, Lake Mulwala, was 610mm and 5.0kg. Management restrictions on the recreational and commercial fisheries for Murray cod, based on the results of this and previous studies are outlined. Manuscript received 12 October 1998, accepted for publication 18 November 1998. KEYWORDS: Australian inland fisheries, breeding season, fecundity, Maccullochella, matu-ration age, Murray cod, reproductive cycle. INTRODUCTION Despite the importance of the Murray cod, Maccullochella peelii peelii (Mitchell) in the inland fisheries of south-eastern Australia, and the decline in abundance and reduction in distribution since the 1950's (Rowland 1989), no quantitative study of the reproductive biology of the species in the Murray-Darling river system has been pub-hshed. Gooley et al. (1995) studied the reproductive cycle and gonadal development of Murray cod in Lake Charlegrark and adjacent farm dams in western Victoria; however, this is an introduced, self-maintaining population and aspects of its biology differ from natural populations (Anderson et al. 1992; Gooley 1992). Studies of Murray cod held in earthen ponds have provided some information on the reproductive biology of the species. Cod spawn adhesive eggs onto firm substrates such as hollow logs, pipes and clay banks in spring and early summer (Lake 1967a; Rowland 1983; Cadwallader and Gooley 1985). Lake (1967a) found that a slight 'runoff of water into a pond induced cod to spawn, but later studies by Rowland (1983) and Cadwallader and Gooley (1985) demonstrated that spawning was not dependent on a rise in water level in ponds. Emryology and larval development in Murray cod were described by Dakin and Kesteven (1938) and Lake (1967b), and there is paternal protection of eggs during incubation (Rowland 1983). The diet and Proc. Linn. Soc. n.s.w., 120. 1998

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Aspects of the reproductive biology of Murray cod, Maccullochella peelii peelii

S J Rowland
Proceedings of The Linnean Society of New South Wales 120: 147-162 (1998)

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