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AB 9:131-138 (2010)  -  DOI:

Incorporating heterogeneity into growth analyses of wild and captive broadnose sevengill sharks Notorynchus cepedianus

J. Matias Braccini1,2,*, Vladimir S. Troynikov3, Terence I. Walker2,3, Henry F. Mollet4,5, David A. Ebert5,6, Adam Barnett7,8, Nicholas Kirby9

1Fisheries Centre, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
2Department of Zoology, University of Melbourne, Parkville, Victoria 3052, Australia
3Marine and Freshwater Fisheries Research Institute, Fisheries Victoria, Department of Primary Industries, PO Box 114, Queenscliff, Victoria 3225, Australia
4Monterey Bay Aquarium, 886 Cannery Row, Monterey, California 93940, USA
5Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, California 95039, USA
6South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa
7TAFI Marine Research Laboratories, Private Bag 49, Hobart, Tasmania 7001, Australia
8CSIRO Marine and Atmospheric Research, PO Box 1538, Hobart, Tasmania 7001, Australia
9Curatorial Department, Melbourne Aquarium, King St., Melbourne, Victoria 3000, Australia

ABSTRACT: Growth estimates for shark species are mostly derived from length-at-age data, where age information is commonly obtained from hard structures such as vertebrae and dorsal-fin spines. Unfortunately, hard structures cannot be used for estimating the age of many shark species, particularly those occurring in deep water or belonging to ancient groups. Alternative methods are therefore required for the estimation of growth for these shark groups. The broadnose sevengill shark Notorynchus cepedianus has very poorly calcified vertebrae that cannot be used for age and growth estimations. Three stochastic versions of the von Bertalanffy-Fabens growth model with random parameter k were fitted to length-increment data of captive and of wild tagged and recaptured N. cepedianus from southeastern Australia, California and southern Africa. The model based on a gamma distributed parameter k provided the best fit to the data. Captive females and wild females showed the highest and lowest values of mathematical expectation E[k], whereas wild males and wild females showed the lowest and highest values of mean maximum length L, respectively. For a time interval of 1 yr, captive females had the highest length increment, whereas wild females had the lowest length increment. Our approach allows accounting for the natural heterogeneity of growth in the estimation of the growth parameters of N. cepedianus, which has not been done previously for captive and wild sharks. This the first study to provide a representative set of growth parameters for male and female N. cepedianus, which is crucial information for the modelling of the population dynamics of this top predator.

KEY WORDS: Growth heterogeneity · Notorynchus cepedianus · Stochastic model · Phenotypic plasticity

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Cite this article as: Braccini JM, Troynikov VS, Walker TI, Mollet HF, Ebert DA, Barnett A, Kirby N (2010) Incorporating heterogeneity into growth analyses of wild and captive broadnose sevengill sharks Notorynchus cepedianus. Aquat Biol 9:131-138.

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