Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences

Comparison of deterministic growth models fitted to length-at-age data of the piked spurdog (Squalus megalops) in south-eastern Australia

J. Matías Braccini A B C , Bronwyn M. Gillanders A , Terence I. Walker B and Javier Tovar-Avila B
+ Author Affiliations
- Author Affiliations

A Southern Seas Ecology Laboratories, Darling Building DP 418, School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia.

B Primary Industries Research Victoria, PO Box 114, Queenscliff, VIC 3225, Australia.

C Corresponding author. Email:

Marine and Freshwater Research 58(1) 24-33
Submitted: 20 April 2006  Accepted: 14 September 2006   Published: 30 January 2007


Age and growth estimates of Squalus megalops were derived from the first dorsal fin spine of 452 sharks, ranging from 274 to 622 mm total length. Age bias plots and indices of precision indicated that the ageing method was precise and unbiased. Edge analysis of the enameled surface of whole spines and similarities in the banding pattern deposited in the enameled surface of spines and in spine sections supported the hypothesis of annual band formation. Multiple versions of two growth models were fitted to length-at-age data, from which a two-phase von Bertalanffy model produced the best fit. For males, the change in growth rate corresponded with size-at-maturity, whereas for females, the change was slightly before size-at-maturity. Regardless of the growth model used, growth rate of females (0.034 to 0.098 years–1) was very low, making S. megalops highly susceptible to overexploitation by fisheries.

Additional keywords: age, AIC, Gompertz, Squalidae, von Bertalanffy.


We are grateful to P. Risley, G. Richardson and the crew of fishing vessel ‘Nungurner’ for assistance with sample collection, to G. A. McFarlane and colleagues from the Pacific Biological Station and to G. Watson and M. J. Smale from Port Elizabeth Museum at Bayworld for reading a sub-sample of spines, to S. Irvine for comments on ageing techniques, and to M. Araya and V. Troynikov for comments on growth models. This research was supported by an International Postgraduate Research Scholarship and a University of Adelaide Postgraduate Research Scholarship to J.M.B. and an Australian Fisheries Research and Development Corporation grant (FRDC 2002/033) to T.I.W. B.M.G. was supported by an Australian Research Council QEII Research Fellowship. Funding for field and laboratory components was provided by Sea World Research and Rescue Foundation, Project Aware, Royal Zoological Society of New South Wales, Nature Foundation SA (Nature Foundation South Australia) and Royal Zoological Society of South Australia.


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